best practices in postharvest management of leafy

Proceedings

Antonio L. Acedo Jr.Katinka Weinberger

Editors

25-27 October 2007Hanoi, Vietnam

Best Practices in Postharvest Management of Leafy Vegetables in Greater Mekong Subregion Countries

Best Practices in Postharvest Management of Leafy Vegetables

in Greater Mekong Subregion Countries

AVRDC - The World Vegetable Center Shanhua, Taiwan

Best Practices in Postharvest Management of Leafy Vegetables in Greater Mekong Subregion Countries Proceedings of a GMS workshop 25-27 October 2007 Hanoi, Vietnam

Antonio L. Acedo Jr. Katinka Weinberger Editors

AVRDC - The World Vegetable Center AVRDC - The World Vegetable Center is the leading international nonprofit organization committed to alleviating poverty and malnutrition in the developing world through the increased production and consumption of safe vegetables. AVRDC - The World Vegetable Center P.O. Box 42 Shanhua, Tainan 74199 TAIWAN Tel: +886 6 583 7801 Fax: +886 6 583 0009 Email: [email protected] Web: www.avrdc.org AVRDC Publication No: 09-731 ISBN 92-9058-178-6

Editor: Maureen Mecozzi

AVRDC Publication Team: Kathy Chen, Vanna Liu, Chen Ming-che, Shiu-luan Lu

© 2009 AVRDC - The World Vegetable Center Citation Acedo AL Jr., Weinberger K, editors. 2009. Best practices in postharvest management of leafy vegetables in Greater Mekong Subregion countries: Proceedings of a GMS workshop, 25-27 October 2007, Hanoi, Vietnam. AVRDC Publication No. 09-731. AVRDC - The World Vegetable Center, Taiwan. 165 p.

Organizers AVRDC - The World Vegetable Center, ADB Postharvest Project Office Vientiane, Laos Research Instituted of Fruits and Vegetables Hanoi, Vietnam

Funding Asian Development Bank, through RETA 6376

Workshop participants

Front (L-R): Ms. Nguyen Thi Hanh, Vietnam; Ms. Nguyen Thi Thuy Linh, Vietnam; Ms. Win Win Kyi, Myanmar/ AVRDC-WVC Small Enterprise Advisor, Dr. Sasitorn Tongchitpakdee, Thailand (Processing Expert); Dr. Chu Doan Thanh, Vietnam; Dr. Antonio Acedo Jr., Philippines/AVRDC-WVC Regional Project Coordinator, Dr. Chen ZongQi, China, Dr. Lemuel Diamante, Philippines (Processing Expert) Back (L-R): Mr. Borarin Buntong, Cambodia; Mr. Nguyen Dinh Hung, Vietnam; Dr. Varit Srilaong, Thailand; Dr. Kyaw Nyein Aye, Myanmar; Ms. Luong Thi Song Van, Vietnam; Dr. Sirichai Kanlayanarat, Thailand; Dr. Li Hong, China; Dr. Li YunShou, China; Mr. Thongsavath Chanthasombath, Lao PDR; Mr. Chansomone Phomachan, Lao PDR; Mr. Nguyen Khac Trung, Vietnam; Mr. Nguyen Duc Hanh, Vietnam

Contents Acknowledgements

iii

Foreword

iv

Part 1: Problems and Needs of Leafy Vegetable Value Chains in Poverty-stricken Upland Areas in CLV and Available Country Interventions

1

Problems and Needs of Leafy Vegetable Value Chains in Selected Upland Areas in Cambodia and Available Country Interventions Mr. Borarin Buntong

2

Problems and Needs of Leafy Vegetable Value Chains in Selected Upland Areas in Lao PDR and Available Country Interventions Mr. Thongsavath Chanthsombath

9

Problems and Needs of Leafy Vegetable Value Chains in Selected Upland Areas in Vietnam and Available Country Interventions Dr. Chu Doan Thanh

17

Workshop Summary

25

Part 2: Postharvest Technologies for Fresh Leafy Vegetables

27

Postharvest Technologies for Fresh Leafy Vegetables in Myanmar Dr.Kyaw Nyein Aye

28

Postharvest Technologies for Fresh Leafy Vegetables in Yunnan, China Dr.Chen ZongQi

37

Postharvest Technologies for Fresh Leafy Vegetables in Thailand Dr.Sirichai Kanlayanarat

44

Postharvest Technologies for Fresh Leafy Vegetables Dr.Antonio Acedo Jr.

53

Workshop Summary

83

Part 3: Processing Technologies for Fresh Leafy Vegetables

84

Processing Technologies for Leafy Vegetables in Myanmar Ms. Win Win Kyi

85

Processing technologies for Leafy Vegetables in Yunnan, China Dr.Li Hong

92

Processing Technologies for Leafy Vegetables in Thailand Dr.Varit Srilaong

104

Processing Technologies for Leafy Vegetables in the Philippines and Other Parts of the World Dr.Lemuel Diamante

114

Processing Technologies for Leafy Vegetables Outside GMS Dr.Sasitorn Tongchitpakdee

133

Workshop Summary

144

Part 4: Concluding Discussion

146

Upland Agriculture Development in Yunnan, China Dr. Li YunShou

147

Summary of General Discussion

151

Annex

152

Program

153

Participants

159

Acknowledgements AVRDC - The World Vegetable Center and workshop participants gratefully acknowledge financial support from the Asian Development Bank through the RETA 6376 project. The organizers also thank the people who assisted in the preparations for the workshop and who facilitated and accommodated the group during the study tour.

iii

Foreword Postharvest technology (PHT) is crucial for perishable commodities such as leafy vegetables to bring down losses, improve marketing, and increase farm returns. It is of particular importance in the Greater Mekong Subregion (GMS), one of the world’s leading vegetable producers and consumers, where the vegetable industry is seriously constrained by high postharvest losses and poor marketing systems. Initiatives to promote the postharvest sector could fuel economic growth, promote rural sustainability, and ease the problems of poverty, unemployment, and malnutrition in developing countries. PHT enables countries to participate effectively in domestic and international trade in light of increased competition due to trade liberalization and market reforms. AVRDC - The World Vegetable Center designed and instituted two PHT initiatives for vegetables in GMS funded by the Asian Development Bank (ADB). The new ADB RETA 6376 project pursues PHT development for leafy vegetables, targeting small farmers and processors in upland areas in Cambodia, Lao PDR, and Vietnam. This project complements the ongoing initiative on fruit and vegetables (ADB RETA 6208). The ADB RETA 6376 workshop on Best Practices in Postharvest Management of Leafy Vegetables in GMS Countries held in Hanoi, Vietnam on 25-27 October 2007 sought to build the groundwork for future PHT research and development work for leafy vegetables in the region. The specific objectives of the workshop were to:

examine the needs and problems of leafy vegetable farmers and other supply chain actors in upland areas of Cambodia, Laos, and Vietnam, and the existing country initiatives addressing those needs/problems

review and document the fresh produce handling and processing technologies for leafy vegetables available in GMS and elsewhere

identify PHT to be developed and formulate the R&D details

foster regional cooperation to advance the vegetable industry in GMS countries

The workshop gathered PHT experts, key project players and other development workers in GMS to discuss and analyze the initial findings of surveys on leafy vegetable value chains in upland areas of Cambodia, Laos, and Vietnam. Existing country interventions were examined in Session 1, and

iv

experiences shared in postharvest handling (Session 2) and processing (Session 3) of leafy vegetables, including indigenous techniques and those in commercial practice with particular emphasis on simple, low-cost innovations. Session 1 concluded with a list of priority problems/needs; Sessions 2 and 3 with postharvest handling and processing technologies to be developed by the Cambodia, Laos, and Vietnam teams, respectively. Paper presentations preceded each workshop session. Best Practices in Postharvest Management of Leafy Vegetables in GMS Countries contains the papers presented in each session and the summary of the following workshop discussion. It has four parts: The first three parts correspond to the three workshop sessions, and the last part covers the concluding discussion, including a presentation about China’s experience in developing upland agriculture. This proceeding can serve as a reference for development workers, policy makers and other stakeholders in developing countries aiming to strengthen the vegetable industry through improving value-addition activities after harvest.

Dr. Antonio Acedo, Jr.

Dr. Katinka Weinberger AVRDC - The World Vegetable Center

v

PART I: Problems and needs of leafy vegetable value chains in poverty-stricken upland areas in Cambodia, Laos, and Vietnam, and available country interventions

Problems and Needs of Leafy Vegetable Value Chains in Selected Upland Areas in

Cambodia and Available Country Interventions

Borarin Buntong

Postharvest Technology Laboratory Supervisor/Lecturer and RETA 6376-Cambodia Team Expert Member

Faculty of Agro-Industry, Royal University of Agriculture Phnom Penh, Cambodia

Mong Vanndy

National Coordinator, RETA 6376/ 6208 Project Deputy Director, Kbal Koh Vegetable Research Station

Department of Agronomy and Agricultural Land Improvement Phnom Penh, Cambodia

Introduction Cambodia is one of the least developed countries in the Greater Mekong Subregion. It is located between latitude 10-15oN and longitude 102-108oE. It has 24 provinces, three cities, and a total land area of 181,035 km2. The upland areas are located on the eastern side of the Mekong River.

Vegetables rank second to rice among cultivated crops. Total production area is about 70,000 hectares with annual yield of 460,000 tons (FAO, 1999). Vegetables, particularly the leafy type, serve as a major source of income of many farmers and are the main and cheap source of nutrition for low-income families, especially those living in upland areas. Through the ADB-funded RETA 6376 spearheaded by AVRDC - The World Vegetable Center, development initiatives to introduce postharvest technology (PHT) and expand market opportunities for leafy vegetables were made possible, targeting small farmers and processors in upland areas in Cambodia, Lao PDR, and Vietnam. A major initiative is the leafy vegetable value chain survey to gather benchmark information on present postharvest practices, problems, and needs of farmers and processors to be used as a basis for subsequent R&D and training programs of the project. This paper presents some of the initial findings of the survey in Cambodia.

2 Workshop Proceedings, 25-27 October 2007

Vegetable Value Chain Survey Priority leafy vegetables and survey sites Survey site and crop priorities of Cambodia, Lao PDR, and Vietnam partners were set during the RETA 6376 Inception Workshop held on July 3-5, 2007 in Vientiane, Lao PDR. For Cambodia, Kampong Cham and Siem Reap provinces were identified as the two upland survey areas; common cabbage and Chinese kale were selected as priority leafy vegetables (Fig. 1). Preparatory activities Initial arrangement. The RETA 6376-Cambodia team led by the National Coordinator conducted an exploratory trip to the two provinces in September 2007 to identify specific areas in each province to be covered, make administrative arrangements with local authorities, and identify possible survey respondents.

Figure 1. The two sites (Siem Reap and Kampong Cham) and priority leafy vegetables of

the Cambodia surveys.

Best Practices in Postharvest Management of Leafy Vegetables in GMS Countries 3

Figure 2. Some postharvest practices for fresh leafy vegetables in Cambodia. Top, l-r: field handling of harvested produce; sorting, trimming, cleaning; air drying Chinese kale leaves after washing.

Bottom, l-r: packaging; transport. Survey questionnaire translation. Two questionnaires, one for farmers and the other for processors, sent by AVRDC headquarters (HQ) were translated into Khmer prior to the enumerators’ training. Enumerators’ training. The training for survey enumerators was conducted by the survey expert from AVRDC HQ in the Training Room of Kbal Koh Vegetable Research Station (KKVRS) on 24-28 September 2007. There were 11 participants from KKVRS and Department of Agriculture. During the training, the Khmer translation of the farmer and processor questionnaires was checked, revised, pretested, and finalized. Conduct of survey The survey in Kampong Cham was conducted on 1-5 October 2007 and the survey in Siem Reap was conducted on 6-9 October 2007. As planned, 100 respondents were covered in each province, for a total of 200 respondents. However, the target number of processors was not met, similar to the Lao and Vietnam surveys. Overall, only four processors of common cabbage (no processor of Chinese kale), all from Kampong Cham, were interviewed; the rest were farmers.


Initial findings

The RETA 6376-Cambodia team expert member from the Royal University of Agriculture who handled data input was trained by the AVRDC-HQ survey expert in survey data encoding. The following are some initial findings of the survey: Harvesting and field handling. Harvesting of cabbage and Chinese kale is done manually (Fig. 2a). The time of harvesting depends mainly on the order from the collector. The harvested produce may be left in the field to dry (cabbage) or brought to a packing area near the field. Sometimes, packing is done in the field. Some of the problems identified are as follows:

improper maturity

loose handling (no container)

careless handling resulting in leaf crushing and/or head bursting

exposure to the sun

Packinghouse operations, packaging, and transport. At the packing area, the produce is trimmed, cleaned, and sorted (Fig. 2b-c). Some outer leaves of common cabbage are removed, while for Chinese kale, some farmers separate the leaves individually. Cabbage usually is not washed; Chinese kale is washed and air-dried. There is no quality standard used during sorting. Collectors dictate quality criteria for acceptance. The produce is transported unpacked, or packed in bamboo basket of different shapes and sizes (Figure 2d-e), plastic bags, or sacks. Transport is done by small truck (Fig. 2f) or motorcycle with or without trailer. Some problems observed:

large containers that could result in high compression damage and increase the tendency of handlers to drop the container due to its heavy weight

overpacking of containers

mixing of many types of containers of produce in the transport load without proper arrangement (improper stacking)

overloading of transport load

inability of plastic bag to protect the produce

loose transport (produce transported without container)

exposure to sun and rain during transport

delays during transport or distribution


Storage. Farmers do not have storage facilities. The produce is kept in a shaded area of the house or collected immediately by collectors and wholesalers. Losses of produce during handling and transport to market are usually passed on by collectors and wholesalers to the farmers by requiring them to provide a weight allowance such as 1-3 kg additional weight per unit order. Processing. Chinese kale is usually marketed and consumed fresh. Cabbage is consumed fresh and also is processed, mainly pickled (Fig. 3). The usual procedure includes removal of outer leaves, slicing the cabbage head into quarters, salting, and fermentation for 1-2 days. Aside from food safety concerns, some problems noted by processors include:

short shelf life of 1-3 days

fast color deterioration

no uniform quality

lack of skill and knowledge in processing

no enough capital and lack of labor General problems/needs. The survey found that farmers and processors need training in PHT to improve their knowledge and skills to operate a profitable enterprise, and require assistance in sourcing capital.

Available Interventions Addressing Postharvest Problems Some farmers use their own creativity to reduce losses of cabbage and Chinese kale as shown in Figure 4. Observed traditional innovations include:

use of fresh banana leaves to line of bamboo basket to protect the produce from the sharp edges of the container

proper arrangement of Chinese kale leaves inside the container to minimize leaf tearing and crushing

individual wrapping of cabbage heads with old newsprint

use of plastic bags to minimize weight loss, which is a form of modified atmosphere packaging

exposing the cut butt end of cabbage heads to the heat of the sun for 1-2 hours before collection, to allow the cut end to dry and minimize bacterial soft rot

washing Chinese kale to allow rehydration aside from cleaning the produce


The fermentation process to produce pickled cabbage is a traditional technique, although it needs improvement to address the problems encountered. There is no PHT development for leafy vegetables in research and academic institutions. Aside from the scarcity of trained personnel in PHT, there is a lack of funding support for leafy vegetable PHT research and development.

Figure 3. Fermented common cabbage in retail

market display in Cambodia.

Figure 4. Some indigenous/present postharvest techniques

for leafy vegetables.


Conclusion

The survey opens up opportunities for proper application of development initiatives. The problems and needs identified are give only a partial picture of the situation, but do indicate that the actions needed are consistent with the objectives of development projects such as RETA 6376.



Lao PDR and Available Country Interventions

Thongsavath Chanthasombath

National Coordinator, RETA 6376/6208 Project Deputy Director, Crop Multiplication Center, Department of Agriculture

Vientiane, Lao PDR

Introduction The Lao PDR economy is agriculture-based, similar to other Greater Mekong Subregion (GMS) countries. With a land area of 236,800 km2 and a population of more than 6 million, Lao PDR is located at the heart of GMS, bordering with Cambodia, China, Myanmar, Thailand, and Vietnam (Fig. 1). The country could play a strategic role in intraregional trade of agricultural produce. In line with the government’s policy and the Ministry of Agriculture and Forestry’s strategy to modernize agriculture and promote exports, together with market-oriented economic liberalization, dramatic improvements in agriculture were achieved. Collaboration with development agencies that share common goals and objectives is being pursued, including the AVRDC-initiated and ADB-funded PHT programs for vegetables (RETA 6376 and RETA 6208). Vegetables are the second most important agricultural crops after rice. Total cultivated area is 85,710 hectares, producing 744,450 tons of produce (DOA, 2005). Leafy vegetables account for about 50% of the total vegetable production, with area and volume of production of 45,240 hectares and 356,610 tonnes, respectively. Vientiane Province is the major upland growing area, located north of the capital, Vientiane; Champasak is the leading vegetable-producing province at the southern tip of the country on the border with Cambodia and Thailand. PHT development for leafy vegetables was launched through RETA 6376. One major activity is the value chain survey targeting small farmers and processors in selected upland areas. This paper presents some of the initial findings of the survey in Lao PDR.


Vegetable Value Chain Survey Priority leafy vegetables and survey sites During the RETA 6376 Inception Workshop on July 3-5, 2007 in Vientiane, common cabbage and Chinese/green mustard were identified as the priority crops, while Vang vieng and Hinheub (in place of Kasy) Districts of Vientiane Province were selected as the survey sites. After further consultation with the provincial agriculture agency, Kasy District was reinstated as a survey site as originally proposed (Fig. 1). Preparatory activities Initial arrangement. The National Coordinator, Director-General of the Department of Agriculture, and the RETA 6376/6208 Regional Project Coordinator held a meeting with officials of the provincial agriculture agency at the provincial capital, Phonhong. The team received assurances of support for the project and assistance in other requirements of the survey, such as identification of respondents. District agriculture staff (DAS) were selected to be survey enumerators. The DAS attended enumerators’ training a week later.

Figure 1. The two sites (Vang vieng and Kasy districts)

of the Lao PDR surveys.


Figure 2. Some postharvest practices for fresh leafy vegetables in Lao PDR. Top, l-r: Loose hauling and packing in bamboo basket. Trimming

of outer leaves and packing in plastic bag. 68-kg capacity bamboo basket. Bottom, l-r: Baskets of cabbages awaiting transport. Truckload

of cabbages transported bare.

Survey questionnaire translation. Two questionnaires, one for farmers and the other for processors, sent by AVRDC headquarters (HQ) were translated into Lao prior to the enumerators’ training. Enumerators’ training. The training for survey enumerators was conducted by the AVRDC HQ survey expert in the Training Room of the Crop Multiplication Center (CMC) on 4-7 September 2007. There were 10 participants, 6 DAS and 4 CMC staff including the National Coordinator. The AVRDC-ADB Regional Project Coordinator and Small-scale Enterprise Advisor also attended some parts of the training. During the training, the Lao translation of the farmer and processor questionnaires was checked, revised, pretested, and finalized. Conduct of survey The survey in Kasy District was conducted on 10-14 September 2007 and in Vang vieng from 17-21 September 2007, with 100 respondents from each district, for a total of 200 respondents. Due to a limited number of processors, only 18 processors of both cabbage and mustards were surveyed, eight from


Kasy and 10 from Vang vieng. Selected project staff members were trained by the AVRDC-HQ survey expert to use software for encoding survey data. Initial findings

Farmers. Figure 2 shows some of the postharvest handling practices for cabbage. Cabbages are loosely handled (without packaging containers), packed in big bamboo baskets (usually 68 kg capacity), or trimmed of outer leaves (wrapper leaves) before packing in plastic bags. The major problems and needs of cabbage farmers obtained during the survey are:

Overproduction: Cabbage usually is grown after rice during the dry and cool period of the year, from December to March. When harvest time comes, there is an oversupply of produce and price of cabbage drops drastically.

Overmaturity: This is manifested as cracking and internal browning of the cabbage head. This is a frequent occurrence, as most farmers wait for the order from collectors and wholesalers rather than harvest the crop with no sure market.

Allowance for postharvest loss: Collectors/wholesalers usually require 25% allowance for losses incurred when handling the produce from the farm to the market. Because they usually provide big plastic bags as packing material with 12-kg capacity, farmers fill each plastic bag with 15 kg cabbage. Otherwise, collectors/wholesalers will not buy the farmers’ produce.

Losses due to the use of plastic bags: Use of plastic bags as packing material is beneficial in preventing too much water loss (weight loss). Cabbages are harvested in the morning (0800-1000), packed in plastic bags, piled along the road and sometimes covered by leaves, and picked up by the collectors in the afternoon (1400). Sweating inside the bag is common, a condition that favors rotting during subsequent handling. Plastic bags cannot protect the produce from handling hazards resulting from mechanical damage. High losses due to trimming of damaged leaves and rotten parts (due to bacterial soft rot) of the cabbage head are incurred (Fig. 3).

Need for storage facility: Farmers acknowledged that if they could store their cabbages for at least one month, they could have better control in harvesting and marketing their produce. This is because after one month, the price of cabbage normally increases.

Other forms of loss incurred: Drying of outer leaves, insect-damaged heads


Figure 3. Trimming losses in cabbage due to physical injury and rotting

and leafy wilting and yellowing in Chinese mustard.

Figure 4. Lao technique in Chinese mustard fermentation.


For Chinese/green mustard farmers, the major problems that contribute to postharvest loss are:

Wilting, weight loss and yellowing of leaves (Fig. 3)

Insect damage

No uniform size (small)

Overmaturity: This is manifested by the production of flower stalks, because some farmers have to delay harvest to wait for orders from collectors and wholesalers.

Allowance for postharvest loss: For green mustard, farmers are required to provide1 kg allowance for loss per 12 kg plastic bag of produce. For Chinese mustard, this is not required.

No storage facility: Farmers preferred to wait for orders from collectors and wholesalers rather than harvest the crop at the right maturity. The practice of soaking stems in water can keep mustards for only one day; then, wilting and yellowing rapidly develop. Farmers need to extend storage life of mustards.

Limited processing techniques

Processors. Figure 4 illustrates the Lao technique in fermented mustard processing, similar to that practiced for common cabbage. Sorting is first done followed by separating individual leaves, washing, adding and mixing with salt, and fermenting in a pot for 1-2 days. Prior to fermentation, the vegetable is mixed again with salt, monosodium glutamate, and rice water. The major problems and needs of processors are:

Short shelf life: Fermented mustard or cabbage usually lasts for only 1-3 days, depending on the salt concentration used.

Rapid quality loss: The fermented vegetable rapidly deteriorates in aroma (foul odor development), color (from green to brown-yellow) and taste (very sour). If consumed, diarrhea usually results.

Improvement of technique

Available Interventions Addressing Postharvest Problems Figure 5 shows some of the indigenous/traditional techniques of leafy vegetable farmers and processors observed during the survey.

Use of plastic bag for packaging, a form of MAP technique

Cooling by top icing or ice packing


Trimming cabbage and inverted positioning of head

Water dipping and sprinkling

Chinese mustard fermentation (Lao style). The technique is a traditional innovation gained through experience, but still needs improvement to solve or minimize the problems encountered.

There are other interventions being instituted by some development agencies. For example, the District Agriculture and Forestry Office (DAFO) has been implementing training programs on proper production of leafy vegetables including hygienic practices to assure food safety. The National Agriculture and Forestry Extension Service (NAFES) is involved in promoting small enterprise through its ADB-funded Smallholder Project. Some universities and development agencies (e.g. FAO, NGO) are conducting training programs in processing techniques for vegetables. However, PHT research and development interventions are lacking.

Figure 5. Some indigenous postharvest techniques for fresh leafy

vegetables in Lao PDR.

Conclusion

Postharvest handling and processing of the project’s priority leafy vegetables are far from ideal and losses could be very large, especially when there is an oversupply. Some handling and processing techniques are used but may need


to be examined and improved to increase their effectiveness. Other PHT techniques are needed and should be disseminated so that the quality and safety of the produce can be assured.



Vietnam and Available Country Interventions

Chu Doan Thanh, Ph.D. National Coordinator, RETA 6376/ 6208 Project Head, Department of Postharvest Technology

Research Institute of Fruits and Vegetables (RIFAV) Trau Qui, Gia Lam, Hanoi, Vietnam.

Introduction Vietnam is an agricultural country, with 75% of the population (or more than 62 million people) engaged in the agricultural sector. In 2005, Vietnam’s agriculture contributed 19% of the country’s GDP. Despite the great effort of the government to reduce the problem of malnutrition and poverty, the number of people living below the poverty line is still high, especially in remote and upland areas. Vegetables are one of the main sources of rural income. To help farmers, particularly the vegetable growers in upland areas, increase their income and reduce rural poverty, the Asian Development Bank through AVRDC - The World Vegetable Center is implementing a number of technical assistance programs such as RETA 6208 “Improving rural livelihoods through development of vegetable-based postharvest technologies in Cambodia, Lao PDR and Vietnam (CLV)” and recently, RETA 6376 “Support of vegetable value chains in GMS countries for prosperity and poverty reduction.” As one of the initial activities of RETA 6376, surveys of vegetable value chains in selected upland areas of Cambodia, Laos, and Vietnam were conducted. In Vietnam, the national partner is the Research Institute of Fruits and Vegetables (RIFAV). This paper describes some preliminary findings of the survey conducted in Vietnam.

Vegetable Value Chain Survey Preparatory activities Initial arrangement. An exploratory trip to the selected survey sites, Lac Thuy and Thanh Chuong districts, was conducted on 23-25 August 2007 by


the RETA 6376-Vietnam team led by the National Coordinator. The team met and discussed with authorities and staff of local departments of agriculture, people’s committees, women’s associations, and farmer associations responsible for the agriculture sector in the two districts. The local authorities strongly supported the activities of the project. The team also received strong commitment from local authorities to provide necessary assistance during the implementation of project activities. To better understand farmers’ needs and finalize the project’s priorities, the team also visited vegetable farmers and local markets where leafy vegetables are sold. Survey sites and priority leafy vegetables. The exploratory trip finalized the areas from each district to be covered in the survey and the priority leafy vegetables.

Survey sites and farmers to be interviewed Lac Thuy district: 100 farmers from four communes - Chi Ne town, Phu Lao, Lien Hoa, and Dong Tam Thanh Chuong district: 100 farmers from four communes - Thanh Linh, Thanh Thinh, Thanh Lien, and Thanh Van Priority leafy vegetables Based on the discussion with local farmers and authorities, the priority leafy vegetables identified earlier during the RETA 6376 Inception Workshop on 3-5 July 2007 in Vientiane, Lao PDR, had to be revised. The final priority crops were:

Chinese mustard

Common cabbage

Kangkong

Leafy pumpkin (optional) Survey dates Lac Thuy: 3rd week of September Thanh Chuong: 4th week of September

Enumerators’ training. To ensure smooth implementation of survey activities, RIFAV in collaboration with AVRDC - The World Vegetable Center headquarters and AVRDC’s Laos-based ADB Postharvest Project Office organized and conducted the training for enumerators at RIFAV on 10-14 September 2007. There were eight participants, five from the Department of Economics and Marketing and three from the Department of Postharvest


Technology. During the training, the farmer and processor questionnaires were revised, pretested, and finalized. Conduct of survey Although the RIFAV team was already experienced in conducting surveys based on previous experience in the RETA 6208 project, the team needed the expertise from the survey expert from AVRDC headquarters to refresh their knowledge and skills, which was achieved when the expert joined the team for some parts of the survey. Highlights of the survey in each site are as follows:

Lac Thuy District Date: 21-27 Sept 2007 Number of farmers interviewed: 88 Number of processors interviewed: 12 Total number of respondents: 100 Thanh Chuong District Date: 29 Sept-5 Oct 2007 Number of farmers interviewed: 98 Number of processors interviewed: 2 Total number of respondents: 100

Initial findings

The survey data were inputted by RIFAV survey team and sent to AVRDC for analysis. Some preliminary findings based on the data:

a) The average vegetable production area of farmers is 708 m2, of which 497 m2 or about 70% is devoted to leafy vegetables. b) The main vegetables are Chinese mustard, cabbage, kangkong, tomato, and leafy pumpkin. Chinese kale seemed to be a minor vegetable. c) Handling and processing of leafy vegetables is far from ideal and losses could be very high, especially at peak season. Main problems are rapid wilting, rotting, and inability to sell the vegetable at a good price due to lack of postharvest techniques such as storage, handling treatments, and processing.


d) Some handling and processing techniques are used, but may need to be examined and improved to increase their effectiveness.

Available Interventions Addressing Postharvest Problems There are already techniques in harvesting and field operations such as the right maturity, harvest time, harvest technique, harvest containers and tools to use, temporary storage in the field, and hauling the produce to the packing place. Some farmers also clean, sort, trim, and/or bunch the produce. RIFAV has also developed a simple, low-cost hydrocooling facility. In packaging, some materials with specific shapes and sizes can be recommended, but may need to be examined for leafy vegetables. Temperature and humidity control during storage and other measures such as avoiding exposure to ethylene sources, direct sun light and heat sources, and pests are available. In processing, RIFAV has developed a fermentation technique for Chinese mustard (Fig. 1). The specifications of the technique are as follows:

a) Chinese mustard is usually harvested at a late stage of maturity to ensure soluble solids of 8-10%, of which sugar is about 4% and protein 1-2%—the most appropriate condition for lactic fermentation. b) Table salt: use dry salt without contaminating matter. Do not use deliquesced salt for making a salt solution of 12-15%. c) Preparation of raw material: Old outer leaves and too young leaves as well as rotten and heavily damaged leaves should be removed. The upper parts of the leaves should be cut and set aside. Long leaves are cut into shorter sections. The Chinese mustard is washed with clean water to remove foreign matter, dust, and surface microorganisms. The vegetable is dried by leaving in shade with natural air circulation until no excess water is on the leaf surface. Proper weighing is done for accurate preparation of recipe. The weighed vegetable is loaded into a container made from plastic, glass, porcelain, etc. d) After packing the vegetable into containers, the container is filled with the prepared salt solution until all the vegetable is below the surface of the solution. The vegetable should be covered by a plastic or bamboo grid to keep it submerged.


e) Pressing: The container content is pressed by putting a load on the surface to the vegetable remains in the solution. The load weight is calculated at approximately 50% of total vegetable weight. f) Storage: The pickled vegetable is ready after 6-8 days. Care must be taken to ensure that foreign matter and other contamination sources do not fall into the container. If black scum forms on the vegetable surface during pickling and storage the product should be removed immediately and discarded, and the container should be cleaned and sterilized.

RIFAV has also developed a canning technique for fermented head cabbage and Chinese mustard. Fermented leafy vegetables usually have a very short shelf life of up to 3-4 days. There are other ways to prolong the shelf life and preserve the quality for up to six months using further processing techniques such as preserving in airtight pasteurized/sterilized containers like jars, cans, or plastic pouches. The technique is shown in Figure 2.


Figure 1. Flowchart for Chinese mustard fermentation technique

developed at RIFAV.


Figure 2. Flowchart for fermented cabbage and mustard canning developed at RIFAV.

The canning technique has the following procedures: a) Good quality fermented head cabbage and Chinese mustard must be used. b) Washing is done by soaking the vegetable in clean water for 5-10 minutes to remove possible contamination matters.


c) Surface drying is done with natural wind by leaving the fermented vegetables in the shade until there is no excessive water condensation seen on the product surface. d) Containers are cleaned and pasteurized. Empty jars and plastic pouches are cleaned by brushing and sterilizing using steam. e) The jars/pouches are carefully loaded to full capacity with the fermented vegetable. f) Ingredients (salt, food acid, and preservatives): The concentration of solution depends on the acidity and salt contents in the fermented vegetables. In most cases, the solution contains 0.5% acidity and 4% salt. Dissolve the ingredients in water, mix well, and filter it to remove dust and other foreign matter, and boil. The containers with fermented vegetables are filled with the solution. The solution temperature at filling should be around 80oC. The filling volume should be as much as 40% compared to the container net weight. To avoid re-contamination of products, the containers should be capped/sealed as soon as possible. In most cases, capping is done manually. For the plastic pouches, sealing is done by vacuum plastic sealer. g) Pasteurization: The pasteurization regime for glass jars (500 ml volume) is as follows:

20′ – 20′ – 20′ - - - - - - - - - -

78°C The pasteurization regime for plastic pouches (500 g) is as follows:

15′ – 20′ – 30′ - - - - - - - - - -

78°C h) Cooling: After pasteurization, the products should be cooled down as soon as possible until the containers’ surface temperature reaches about 40oC. i) Temporary storage: As usually practiced, the products are subjected to temporary storage for at least two weeks to examine any possible defects. j) Labeling and packing: After temporary storage, defect-free containers, can be labeled and packed into carton boxes.


Workshop Summary Summary of problems/needs of farmers and processors based on leafy vegetable value chain surveys of Cambodia, Laos, and Vietnam partners and available country interventions.

Country Chain Level Problems/Needs Existing/Developed Techniques

Harvest/field: proper maturity; damage (leaf crushing/tearing, head bursting) due to careless operation and loose handling (without container); wilting due to exposure to sun and delays

Cabbage head with cut butt end exposed to sun right after harvest and before collection, apparently to allow drying up of the butt end to discourage soft rot development

Farmers

Packhouse, Storage, Transport: over-trimming, loose handling, improper container (too big, use of sack, improper stacking, overloading; no storage facility /technique; rotting, wilting and yellowing result to trimming losses

Use of plastic bag (modified atmosphere packaging or MAP) with individual wrapping with newsprint

Cambodia (common cabbage; Chinese kale)

Processors Fermented cabbage: short shelf life of 1-3 days; not uniform quality Other processed products: no processing technique for Chinese kale and dehydration technique in cabbage

Traditional fermentation/pickling method


Country Chain Level Problems/Needs Existing/Developed Techniques

Cabbage: During over-supply (production peak), need storage for at least one month when prices start to go up; Over-maturity (cracking and internal browning) as farmers wait for order rather than harvest the crop; plastic packs (MAP films) provided by collectors but high transport losses due to damage (plastic bag could not protect produce from handling hazards) and rotting (favored by sweating inside the bag); losses passed on to farmers providing 25% allowance for loss (e.g. for 12 kg pack, 3 kg more added)

MAP Farmers

Chinese/green mustards: losses due to over-maturity (flowering), yellowing, wilting; for green mustard, 1 kg allowance for loss per 12 kg pack

MAP

Lao PDR (common cabbage; Chinese/ green mustards)

Processors Fermented mustards/cabbage: same as Cambodia

Fermentation method

Farmers General needs: proper harvest/field operations, postharvest treatments, packaging, storage; specific problems similar to Cambodia and Lao situations

Proper handling recommended elsewhere usually adapted by farmers

Vietnam (common cabbage; Chinese mustard; kangkong)

Processors Fermented mustard/cabbage: same as Cambodia and Lao PDR

Fermentation technique at RIFAV; plastic packing, bottling, canning to prolong shelf life


PART II: Postharvest technologies for fresh leafy vegetables

Postharvest Technologies for Fresh Leafy Vegetables in Yunnan, China

Chen ZongQi

Associate Professor Agricultural Environment and Resources Research Institute

Yunnan Academy of Agricultural Sciences Kunming, Yunnan, China

Introduction China produces more than 583 million tons of vegetables per year, or nearly 50% of the world’s production. However, postharvest losses are a significant problem and are estimated at 25-30% of production, accounting for more than 70 billion yuan (>9 billion USD) per year. Yunnan Province grows a number of vegetables on about 583,000 hectares, producing about 10.4 million tonnes for domestic use, to supply other provinces, and for export. The main vegetables are as follows: Leafy vegetables: lettuce (head and leaf types to Southeast Asia, Japan, Hong

Kong, Beijing, Shanghai, Guangdong), cabbage (Shandong, Guangdong), celery (Singapore, Malaysia, Hong Kong, Shanghai, Beijing, Guangdong, etc.), spinach (Hong Kong, Guangdong, etc.)

Fruit vegetables: sweet bean (Japan, Taiwan), eggplant and bitter gourd (South China), tomato (around China and Southeast Asia), sweet pepper (Japan, Shanghai, Hong Kong, Guangdong)

Flower vegetables: cauliflower (Malaysia), broccoli (Japan, Singapore, Beijing, Shanghai, Hong Kong, Guangdong)

Root, bulb, and tuber crops: radish (Japan, South Korea, Guangdong), carrot (Thailand, Shandong, South China), potato (Southeast Asia, around China), onion (South Korea, Japan, Russia, North China), garlic and ginger (South Korea, Middle East countries, Shandong)

Yunnan produces two types of common cabbage; the big variety, mainly for pickle and dried product processing, and the small variety for the fresh market. Chinese cabbage and leaf mustard are produced for fresh consumption and pickling. Chinese kale is of two types: the leafy type is mainly for fresh consumption, and the stem type for the local market and for supply to Guangdong and Hong Kong.


Proper postharvest handling of fresh vegetables is important to reduce losses between harvest and consumption, maintain quality (appearance, flavor and nutritive value), and ensure safety of the produce. The Yunnan provincial government promotes and supports the development and use of appropriate postharvest technologies to improve quality and market competitiveness of vegetable produce. Government research and academic institutions are spearheading technology development and extension to farmers and other industry users. These development efforts yielded good results, but are not yet sufficient to address the needs of the vegetable industry. Most vegetable farmers and marketers rely on their own techniques to reduce losses and improve marketability of their produce. This paper presents some technologies developed and techniques used by farmers in the handling and marketing of fresh leafy vegetables. Some techniques described here are recommendations, rather than products of research.

Postharvest Losses Postharvest losses of leafy vegetables in Yunnan, China have not been assessed and quantified. However, the problem is prevalent and serious, as farmers incur trimming losses and losses due to wilting and bacterial soft rot (Fig. 1). Leaf yellowing, tearing, crushing, and head bursting (in the case of common cabbage and heading type of Chinese cabbage and lettuce) are also common and contribute to losses.

Postharvest Techniques Harvesting Because of the climate and mountainous terrain of the province, common cabbage, Chinese cabbage, Chinese kale, and mustards are planted and harvested year-round in Yunnan. Harvest maturity of leafy vegetables is estimated based on appearance and/or firmness. If some of the leaves turn yellow, it means the vegetable is ready for harvest. In common cabbage and Chinese cabbage, the head is pressed lightly by hand; if it is tight and hard, the vegetable is already mature. In certain cases, sample heads of common cabbage or Chinese cabbage are cut into two parts to observe the internal stem; if the stem is too long, the head is already overmature. Harvesting is done by hand with the use of a knife. The harvested produce is then placed in collection containers, which may be plastic crates or bamboo baskets with cotton or paper cushioning or padding. The packed


produce is then brought to the packhouse for further processing. Some farmers bring their produce directly to the market, where handling operations are done before display of produce. Packinghouse operations At the packhouse, good quality produce is selected and defective vegetables discarded. Leafy vegetables are usually trimmed using a special knife (Fig. 2). Damaged and senescent leaves are removed; for some vegetables (e.g. cabbage, Chinese cabbage), the butt is trimmed. For leaf mustards, the roots are usually retained and cleaned by washing together with the leaves. The cleaned produce is then sorted based on the buyers’ requirements or based on the national industry standards such as that for Chinese cabbage (Table 1). The cleaned produce is wrapped or bundled (Fig. 2) before packaging. Table 1. Chinese cabbage standards (SB/T 10332-2000)

Grade Quality Specification (kg) Limit

First

Same characters, head tightly, natural color and luster, fresh, clean, without rot, old stem, yellow leaf, peculiar smell, bolting, wormhole, or physical defect

Disqualification vegetables can not over 5%, rotten ones within 1%

Second

Same characters, head tightly, natural color and luster, fresh, clean, without rot, old stem, yellow leaf, peculiar smell, bolting, wormhole, or physical defect

Disqualification vegetables can not over 10%, rotten ones within 1%, weight specification difference with 10%

Third

Same characters, head loose, natural color and luster, fresh, clean, without rot, old stem, yellow leaf, peculiar smell, bolting, wormhole, or physical defect

Largest size per vegetable ≥4.0 Big size per vegetable≥3.5 Medium size per vegetable≥2.5 Small size per vegetable≥1.5 Smaller size per vegetable≥1.0 Disqualification

vegetables can not over 10%, rotten ones within 1%, weight specification difference with 10%


Figure 1. Losses of leafy vegetables in Yunnan, China.


Figure 2. Trimming, cleaning, and bundling of leafy vegetables.


Packaging and transport Some vegetables are directly packed into containers. Different kinds of containers are used for leafy vegetables, depending on the market and value of the produce. For export and high-value leafy vegetables, more rigid and presentable but expensive containers are used such as foam boxes and cartons (Fig. 3). For the local markets, bamboo baskets of different sizes and shapes are used. Some produce is packed in plastic crates or handled loosely (no container) when brought to the market (Fig. 4). Cooling during transport may be done by using wet pads as liners (Fig. 4) or by using ice bottles mixed together with the produce inside the container (Fig. 5). Other techniques in packaging and transport of leafy vegetables include the following:

1. Use of sack liners and cotton-cloth pads and plastic film covers on bamboo baskets.

2. Use of paper, stretchable foam cap or plastic film to wrap cabbages individually or in groups of three such as those for Chinese cabbage.

3. Use of plastic film liner in cartons. 4. Use of foam box with and without newsprint liners 5. Circular arrangement of leaf mustards to protect the leaves from

damage and water loss 6. Use of refrigerated truck with temperatures of 1-4oC.

Storage Simple refrigerated storage facilities have been developed for the storage of fresh produce including leafy vegetables (Fig. 6). Normally, for small-scale plants, refrigerating equipment with room space is enough for storage. For most leafy vegetables, storage is done at 1-2oC and relative humidity of 90-95%. Mixed storage with fresh fruits such as apple, pear, and peach is avoided as these fruit produce high levels of ethylene, which promotes yellowing and senescence of the leafy vegetables. For vegetables to be sold in the local market (wholesale or retail market), the farmers often harvest in the early morning or after sunset, and the harvested produce is covered with wet pads or plastic film for cooling and preventing excessive water loss. For vegetables to be shipped to distant or export markets, the harvested produce is brought to a packinghouse where the different operations are carried out, including cold storage, before transport.


Figure 3. Packaging containers and techniques for leafy vegetables.


Figure 4. Transport practices and techniques for leafy vegetables.

Figure 5. Ice bottles for cooling leafy vegetables inside the container.


Figure 6. Simple refrigeration equipment for the storage of leafy

vegetables.

References

Zhang Pingzhen. 2004. Vegetable fresh keeping, storage, transportation and processing. China Agricultural Press.

Zhen Yonghua. 2000. Practical techniques for vegetable processing. Jindun Press.


Postharvest Technologies for Fresh Leafy Vegetables in Myanmar

Kyaw Nyein Aye, Ph.D.

Associate Professor Yangon Technological University

Insein, Yangon, Myanmar

Introduction Vegetables play an important role in human nutrition. Apart from ascorbic acid (vitamin C), vegetables, particularly the leafy types, are a rich source of essential nutrients such as vitamin A, folic acid, and beta-carotene. A substantial proportion of the carbohydrates found in leafy vegetables contribute dietary fiber. Many therapeutic drugs in alternative medicine originate from extracts of vegetable leaves. In Myanmar, like other Asian countries, people enjoy consuming vegetables in their daily diet. Although there are very few exports of leafy vegetables from Myanmar, some organic leafy vegetables have entered the value chain, and postharvest technology (PHT) is a common practice. PHT preserves freshness of leafy vegetables from the farm to the market. In this report, the status of PHT of fresh leafy vegetables in Myanmar is presented. Organizations and their activities related to PHT are introduced and the use of chitosan, a biopolymer derived from chitin, to prolong shelf life is presented.

Leafy Vegetable Production and Marketing Vegetables are cultivated on 405,000 hectares in Myanmar (MOAI, 2007). Many vegetable crops are grown without inputs. The Pyin Oo Lwin and Inle Lake areas produce a variety of vegetables, while the Bago area specializes in growing okra and roselle leaves. Many kinds of kitchen crops like chili, onion, and garlic are grown in Mandalay and Sagaing areas. Figure 1 shows the vegetable-growing areas in Myanmar while Table 1 shows the crop calendar of some leafy vegetables. For local consumption around Yangon metropolitan area, the big wholesale market (Thirimingalar Zay) is located on the bank of Yangon River. Handling practices are not systematic and almost no PHT is involved, except water


washing. The middlemen/brokers collect the produce from the farm and bring it to the wholesale market. Some brokers have shops in the market and resell to vegetable dealers or retailers. Most vegetables are collected from the farm using cow-driven carts. Some are packed in big bamboo baskets before transport to market, or transported loosely overnight by truck (Fig. 2), arriving at the wholesale market the following morning. When the market is very competitive during the off-season, the growers can enjoy on-farm sales. Normally, the produce is brought to a buying depot. In some areas, there can be a sort of growers' association selling their commodity direct to the wholesalers, who will then bring the produce to city or town markets. Marketing systems vary from region to region and from crop to crop. The main means of transport is truck and the major flow of commodities is to large markets and to the border areas. Retailers also are very active in distribution of fresh produce to local and street markets, and even to consumers’ doorsteps in remote villages and fields. There is no or very few quality assurance system for vegetables. Quality management throughout the commodity chain is based mainly on local knowledge, resources, and traditional wisdom (Aung et al., 2005).

Figure 1. The map showing the annual total sown area of vegetables

(MOAI et al., 2005)


Table 1. The crop calendar for some leafy vegetables and their average yield in a year in Myanmar (MOAI, 2007)

Seasons Yield (tons per acre) Sr.

Crop Name

Major Growing Area Grow Harvest

Unit Average Max

1

Mustard

SGG MDY MGW KCN KYR

Nov

Feb-Mar

Basket (equiv. to 25 Kg)

6 6 6 8 8

11 11 11 11 11

2

Green Gram (Rain) Green Gram (Winter)

MGW SGG MDY YGN PGUe AYW MGW SGG

May-June Nov-Dec

Sep-Oct Feb-Mar

Basket(equiv. to 25 Kg)

10 13 10 10 14 14 10 14

14 15 15 20 20 20 20 20

3 Cabbage SHNs PGUe PGUw

May-July Nov

Aug-Oct Mar

Viss (equiv. to 1.67 kg)

4000 5000

7000 6000

4 Broccoli

SHNs SGG AYW

May-July Oct-Nov

Aug-Oct Feb-Apr

Viss (equiv. to 1.67 kg)

4000 3500

7500 6000

SGG = Sagaing Division, MDY= Mandalay Division, MGW = Magway Division, PGU = Pegu Division,

PGUe = Eastern Pegu Division, PGUw = Western Pegu Division, KCN = Kachin State, KYR = Kayar

State, YGN = Yangon Division, AYW = Ayarwaddy Division, SHN = Shan State, SHNs = Southern Shan

State


Figure 2. Traditional transport of cabbages from the farm to roadside or

collector/wholesaler house using cow-driven cart and transport to markets using pick-up truck.

Figure 3. Packinghouse operations for some vegetables: unloading, hydrocooling in cold water, packing in carton box, cold storage, and

transport in refrigerated trucks.


Postharvest Technologies: Myanmar Experience Packinghouse facility Myanmar has only one packinghouse owned by the Yangon City Development Committee. The facility has three cold rooms with 10-tonne capacity and postharvest equipment such as a hydrocooling facility (Fig. 3). Packaging containers, such as cartons for produce to be exported to Singapore, are fabricated by an exporting company. Upon arrival in the packinghouse, the vegetables, such as lettuce and broccoli, are pre-cooled with 1 oC water containing a disinfectant prior to packing in airtight plastic bags and cartons for cargo flight. Postharvest decay and use of chitosan Postharvest decay and desiccation are the two major causes of short shelf life of leafy vegetables. Decay can be reduced to a certain extent by minimizing mechanical damage and enhancing the natural resistance of produce. Fresh vegetables can be infected before and after harvest by pathogens. Postharvest use of chemical pesticides pose food safety concerns. Postharvest chemical residues can be detected in some leafy vegetables. Table 2 shows the pesticide residues in various leafy vegetables. Table 2. Pesticide residues in various leafy vegetables detected a week after application (Theingi Nwe, 2007).

Pesticide Residue in Green Gram Leaves

Pesticide Residue in Mustard Leaves

Pesticide Residue in Kale Leaves

Days after Pesticide Application Acephate

(ppm) Dimethoate (ppm)

Malathion (ppm)

Chlorpyrifos (ppm)

Malathion (ppm)

Chlorpyrifos (ppm)

1 2.48 3.20 0.34 0.22 0.33 0.06 3 2.40 3.06 0.20 0.02 0.19 0.04 5 2.11 2.76 0.14 ND 0.15 ND 7 0.95 2.65 0.08 ND 0.13 ND

ND = Not detected

There is now a growing need to develop alternative approaches for efficient control of storage diseases. Chitosan, a natural polymer of -glucosamine, was found to control fungal diseases in fruits and vegetables such as tomato, pepper, cucumber, and strawberry. It is also a potential elicitor of plant defense systems such as chitinase (destroys cell wall of pathogens), phytoalexin (antibiotic that is toxic for bacteria and fungi), and proteinase inhibitor (Thazin Han, 2006). Furthermore, chitosan can extend the shelf life of fresh produce (Robert, 1989; Noguchi and Katsumori, 1991). The use of chitosan could provide farmers greater flexibility in postharvest and marketing schedules.


Postharvest handling of organic vegetables The rapid growth of the market for organic crops and advancements in methods to authenticate their origin require a proactive approach to setting acceptable organic farming standards. Systems to detect the presence of agrochemicals would have to be constantly updated in line with the introduction of new pesticides. In Myanmar, the present organic farming system is far from satisfactory. Researchers are currently working to develop organic vegetable farming and the use of chitosan as a biocompatible growth stimulator. To promote organic farming, it is essential that farmers are made aware of optimal procedures to produce safe, high quality crops and alternatives for agrochemicals. National organizations involved in PHT works

The Myanmar Fruit and Vegetable Producer and Exporter Association (MFVPEA) was organized to promote the use of the latest technologies in fruit and vegetable cultivation and value-added manufacturing. One of the key initiatives of MFVPEA would be to set up a special production zone for agricultural exports that would attract local and foreign investment. MFVPEA is targeting regional markets as well as Myanmar consumers. It also is involved in research and training activities, and promoting the consumption of vegetables. MFVPEA organized Myanmar's first ever horticulture show in early May 2007 to encourage fruit and vegetable growing. The four-day activity on Myaypadetha Island near Kandawgyi Lake displayed a variety of fruits and vegetables produced by different regions in the country and had a concurrent seminar on Myanmar fruit, vegetable and flower production, with presentations of research findings and growing techniques, including PHT. Under the Ministry of Agriculture and Irrigation, two key institutions have been doing research on leafy vegetables: Yezin Agriculture University, which is located near the capital Nay Pyi Taw, and the Vegetable and Fruit Research and Development Centre, located in Hlegu Township, Yangon Division. Under the Ministry of Science and Technology and Ministry of Education, some universities such as Yangon Technological University have been conducting agriculture and food science research in leafy vegetables, such as analysis of pesticide residues and application of chitosan. Under the Ministry of Commerce, an organization called Myanmar Agricultural Produce Trading (MAPT) pursues the government’s trade policy by providing assistance for the enhancement of better quality crop production. One of the functional centers of MAPT is the Postharvest Technology Application Center based in Hlegu, serving the postharvest research, development, and extension works for food grain, fruits, and vegetables, and providing a certification system related to quality of crops and analytical results of chemical compositions.


Conclusion PHT exists in Myanmar, but it needs proper attention and action. Only few sectors in agriculture, including leafy vegetable growers, apply PHT. These technologies will play a central role in promoting leafy vegetable production, marketing, and utilization in the future.

Acknowledgement The author would like to thank AVRDC-ADB RETA 6376 project for providing financial support to participate in the workshop and to Yangon Technological University and MFVPEA for the assistance in sourcing knowledge resources in PHT.

References Aung H., Htoo S.H.L. and Aung H.P. 2005. Marketing and Distribution Systems of

Fresh Produce in Myanmar, ISHS Acta Horticulturae 712: IV International Conference on Managing Quality in Chains - The Integrated View on Fruits and Vegetables Quality.

MOAI. 2007. Annual Report for 2006-2007 from Myanmar Agricultural Services, Ministry of Agriculture and Irrigation, Union of Myanmar.

MOAI, UNDP and FAO. 2005. Digital Agricultural Atlas of the Union of Myanmar, issued by Ministry of Agriculture and Irrigation, United Nations Development Programme and Food and Agriculture Organization of the United Nations (CD ROM format)

MOC. 2007. Annual Reports of the Status of Fruits and Vegetables Export submitted by Myanmar Agricultural Produce Trading, Ministry of Commerce, Union of Myanmar.

Noguchi and Katsumori. 1991. Seed Treatment by Chitin Regulator’s Properties. Japan-Kokai Tokyo, Koho, Japan. 0308004

Robert L. E. 1989. Salts of Chitin Derivatives, PCT . into Appl.Wo. 8907395 Thazin Han. 2006. Production of Chitosan from Various Sources for Use as a Plant

Growth Stimulant and Study on the Antifungal Chitinase Activity of Trichoderma harzianum as a Biocontrol Agent, Ph.D. Thesis, Yangon Technological University, Myanmar.

Theingi Nwe. 2007. Investigation on the Behavior and Fate of Pesticide and Their Effects on the Microbial Environment of the Vigna radiata (Green Gram), Brassica rapa (Mustard Green) and Brassica oleracea (Kale) Cultivation, Ph.D. Thesis, Yangon Technological University, Myanmar.


Postharvest Technologies for Fresh Leafy Vegetables in Thailand

Sirichai Kanlayanarat, Ph.D. Head, Division of Postharvest Technology

King Mongkut’s University of Technology Thonburi Thungkru, Bangkok 10140, Thailand

Introduction

Thailand produces several kinds of vegetables across a large area. In 2005, the area of vegetable production was 452,500 hectares with a yield of 4,775,222 tonnes. This production is supplied to both domestic and export markets. The major economic vegetables are chili, baby corn, asparagus, okra, cucumber, tomato, Chinese kale, garlic, red shallot, and ginger. Leafy vegetables are grown all over the country but the major ones are cabbage (Brassica oleraceae var. capitata), Chinese cabbage (Brassica oleraceae var. pekinensis), Chinese kale (Brassica oleraceae var. alboglaba), and leaf mustard (Brassica junceae var. rugosa). The main production areas for cabbage, Chinese cabbage, and leaf mustard are the North and Northeastern parts of the country, while Chinese kale is grown around Bangkok and in the Central and Western regions. Nowadays Thai people consume vegetables at an average of about 38 kg per person per year. The government is trying to increase the rate of vegetable consumption to 50 kg per person per year. The Department of Agriculture is supporting the development of technologies while the Department of Agricultural Extension spearheads the transfer of these technologies to the farmers. The domestic trade in vegetables in the larger cities such as Bangkok is shifting from traditional wet markets to supermarkets as people have more disposable income and a desire for convenience and safe quality produce. Many supermarkets are controlled by global companies from Europe and Japan; to supply these outlets, Thailand is striving to improve the quality of vegetables through the adoption of Good Agricultural Practices (GAP), Good Manufacturing Practices (GMP), and Hazard Analysis and Critical Control Points (HACCP) systems in the supply chain.


Basic Considerations Quality of leafy vegetables Quality is still very much in the “eye of the beholder.” This means appearance is the first factor that concerns the consumer. However, the perception of quality changes as the product moves along the distribution chain. For leafy vegetables, the customer wants to buy a product with fresh, clean, and green appearance, free of obvious defects and decay, not split or bolted, and without pesticide residues. To ensure high marketability and consumer loyalty (repeat purchase), the leafy vegetable should possess both high quality at the time of purchase and high quality when consumed. Factors contributing to quality loss Water loss. Leafy vegetables are living plant parts that mostly contain >90% water. Before harvest, the plant is supplied with a constant flow of water from the soil through the roots, keeping the plant turgid. Whatever water is lost through the transpiration process is replenished through root absorption of soil water. After harvest, this water-replenishing system is cut off, while water loss through transpiration continues, eventually resulting in leaf wilting. A loss of 5-10% of fresh weight would make leafy vegetables appear wilted and become unusable. To extend the usable life of leafy vegetables, the rate of water loss must be slowed down. This can be done by keeping the produce under high humidity and low temperature conditions, avoiding exposure to high air movement, or holding the produce in appropriate packaging material. Mechanical injury. The high moisture content and soft texture of leafy vegetables render them very susceptible to mechanical injury, which can occur at any stage from harvest, transportation, to retail marketing. Physical damage may be due to poor harvesting practices, use of unsuitable field or marketing containers, overpacking or underpacking containers, and careless handling. Mechanical injuries, such as skin rupture and leaf crushing, further increase the rate of water loss, provide entry points for fungal and bacterial pathogens that cause decay, and increase the rate of respiration. High temperature. Exposure of fresh leafy vegetables to high temperatures accelerates quality deterioration. Leafy vegetables left in the sun after harvest may reach temperatures as high as 50oC. As a consequence, water loss and respiration increase. If packed and transported without cooling, wilting rapidly sets in. Similarly, exposure of leafy vegetables to high ambient temperatures prevalent in the tropics shortens shelf life.


Chilling injury. Some types of leafy vegetables are susceptible to injury at low temperatures. Symptoms of chilling injury may not develop until the produce is removed from cold storage and brought to normal market temperature. Chilling injury symptoms may appear as localized or general discoloration of product surface, which degrades quality and marketability. Diseases and pests. Diseases caused by bacteria and fungi generally result to tissue decay or skin blemishes that lower the value of the produce. On the other hand, insect infestation usually occurs before harvest. It is a very serious problem in cabbage, Chinese cabbage, leaf mustard and Chinese kale. The growers need to employ proper insect pest control measure without sacrificing product safety due to pesticide residues. Ethylene effects. Ethylene is a plant hormone that destroys the green color of plants. If leafy vegetables are exposed to ethylene, leaf color changes from green to yellow. Ethylene is produced by all plant parts although at varying degrees, decaying tissues, and smoke or engine exhaust. Exposure of leafy vegetables to ethylene must therefore be avoided. In certain cases, an ethylene removal system can be used.

Supply Chain Management of Leafy Vegetables

System I: Traditional The grower is financed by or committed to a middleman. The middleman receives the crop and sells it in a wholesale market to wet market and to supermarkets (Fig. 1). The grower also may sell the crop directly to the market. This is a low technology system, usually with no temperature control, and relies on selling the produce within one day after harvest. Losses of produce may be very high, particularly when weather conditions are adverse. Many growers of Chinese kale around Bangkok, Ratchaburi, Nonthaburi, Pathumtani, Nakhon Pathom, and Kanchanaburi provinces employ this supply chain system. However, growers of cabbage and Chinese cabbage in Chiang Mai, Petchaboon, and Nakhon Ratchaseema provinces also may use this system.


Figure 1. Traditional supply chain system for leafy vegetables in Thailand.

System II: Corporation A food corporation supplies vegetables to its chain of supermarkets in Thailand. Farmers are contracted to grow vegetables following recommended production practices established by research institutions. Pricing of farmers’ produce depends on prevailing market price. Depending on the crop, the harvested produce is sorted and packed on-farm and brought to the company’s headquarters for subsequent distribution. Other crops are brought to the company’s packinghouse for grading using the company’s quality standards, packing, and holding/storage. The packinghouse is located near the company’s headquarters and distribution center. If distribution cannot be done on the same day of arrival, storage is done in the company’s central cold room. The produce is distributed to the supermarket outlets in refrigerated trucks and displayed on refrigerated shelves.


Figure 2. Corporate supply chain system for leafy vegetables in Thailand.

System III: Royal Project The Royal Project is His Majesty the King Bhumibol Adulyadej’s personal initiative to develop the highlands of Northern Thailand to eliminate opium cultivation, alleviate poverty, and preserve the highland environment. The vegetable growers are the Hill Tribe people in the highlands of Chiang Mai. The vegetables include cabbages and other temperate types. Production techniques are recommended by the project’s researchers. The growers harvest their own vegetables and deliver them to 37 fully-equipped collection centers (Fig. 3). The vegetables then go through the following processes: checking for quantity and quality; cleaning, trimming, checking for chemical residues such as fertilizer and pesticides (if found to be unsafe, the produce is rejected), packing, pre-cooling (if needed), and storage in cold rooms. Each postharvest center has fairly extensive infrastructure and equipment, such as conveyors, carts, crates, measuring devices, displays showing quality guidelines, and cutting and trimming devices. At least one pre-cooling facility is used. Some crops are cooled in different ways. The center has also a cold room for storing perishable crops before transport. Small refrigerated lorries owned and operated by the Royal Project Foundation collect the produce from each Center and take it to the packinghouse in Chiang Mai. This is a large, central collection point usually employing more than a hundred people. Produce is processed and packed to a high standard of efficiency and hygiene. At the packinghouse, produce is checked for quality, trimmed, washed, checked for all chemical residues, and then packed again. Low grade or excess produce is usually sent for food processing. The packed produce is transported to Chiang Mai, Bangkok or


regional markets. Like the local postharvest centers, the packinghouse is fully equipped and has cold storage facilities. The packinghouse itself is temperature- and humidity-controlled to reduce crop wastage. Whether the produce is destined for Chiang Mai, Bangkok, or regional markets, the produce is transported by large trucks. When the produce arrives at the Bangkok Distribution Centre at Kasetsart University, the delivery is again checked for quantity and quality since some produce may have been damaged in transit. After quality check up, the produce is stored in cold rooms. From there, the produce is transported to Doi Kham Stores or to third-party retailers and wholesalers. The aspects of the project that deserve special comment are packing, grading, and the cold chain.

Figure 3. The Royal Project supply chain system for leafy vegetables in

Thailand.

Postharvest Technologies for Leafy Vegetables Controlling water loss Freshness is a very important quality of leafy vegetables. To reduce water loss, the produce is kept under cool temperatures and high relative humidity. The produce is packed in perforated plastic bag or individual film wrap, such as polyvinyl chloride (PVC) film. The type of film depends on the kind of leafy vegetable. Air movement through produce is essential to remove the heat of respiration, but the rate of air movement must be kept as low as possible to avoid excessive water loss.


At ambient temperature condition, leafy vegetables are kept under high humidity. In supermarkets, cabbage and Chinese cabbage are packed in perforated plastic bags (with 4 to 8 holes with 5 mm diameter) or individual wrap with PVC film at shelf temperature of 7oC. If perforated plastic bags are used, the number of holes should not be excessive, because the leafy vegetable will still easily wilt. If the number of perforations is too few, water will condense on the surface of the plastic bag, favoring disease development. For Chinese kale, perforated plastic bags (with 4 to 8 holes) or polyethylene (PE) bags with one open end can be used. In addition, hydrocooling Chinese kale by dipping in 4oC water for 5-10 minutes prior to 7oC storage was found to control water loss and extend shelf life. Controlling high temperature injury High temperature increases the rate of deterioration of leafy vegetables by accelerating leaf wilting and yellowing. After harvest, the produce should be kept in the shade or protected from exposure to sunlight. For Chinese kale, removal of field heat can be done by precooling as mentioned above. The produce has been found to show the freshness quality desired by supermarkets. However, if the produce is to be sold in traditional markets, water spray is enough to reduce field heat. For cabbage and Chinese cabbage, trimming of outer leaves is done before keeping in the cold room (7-10oC) Controlling chilling injury Chilling temperature damages the cell and tissue of susceptible leafy vegetables. Thus, chill-sensitive produce should not be kept at too low a temperature. Leafy vegetables can be kept at 7oC, similar to the temperature of refrigerated shelves in supermarkets. This is particularly true for Chinese cabbage and Chinese kale. If Chinese kale is kept at quite high temperature, leaf yellowing rapidly develops. For common cabbage, temperatures lower than 7oCcan be used. Controlling diseases Leafy vegetables are susceptible to postharvest diseases that render the produce unfit for sale. Postharvest diseases can be spread through field boxes contaminated by soil, decaying produce, contaminated water used to wash produce before packing, decaying rejected produce left lying around the packinghouse, and contaminated healthy produce in packages. Microbial


infection can occur both before and after harvest. The infection after harvest can be found at any time between the field and final consumer. For cabbage and Chinese cabbage, soft rot is a major problem and the pathogen usually infects the cut area at the butt. At the Royal Project packinghouse, a simple technique of applying CaCO3 paste at the butt end is done. The paste is then allowed to dry before packing. Soft rot also will develop on injured skin; damaged leaves are therefore trimmed off to minimize the problem. In Chinese kale, disease pathogens also infect the cut area. It is recommended that a sharp, clean knife should be used, and all containers must be cleaned with decontaminated water. Reducing mechanical injury Because leaf vegetables are susceptible to mechanical injury, proper handling is necessary from harvesting to marketing. Mechanical injuries are usually inflicted during harvesting, field handling, packaging, and transportation. Careless handling of vegetables causes internal browning, which results in abnormal physiological damage or splitting and skin breaks, thus rapidly increasing water loss and the rate of normal physiological breakdown. Skin breaks also provide sites for infection by disease organisms causing decay. For cabbage and Chinese cabbage, the produce must be harvested by retaining 2-3 outer leaves (wrapper leaves) to protect the edible inner leaves from damage during field handling and transport. Plastic crates (15 kg capacity) are recommended. When the produce reaches the packing area or market, it is necessary to trim the wrapper leaves as well as damaged leaves. Middlemen usually pack cabbage or Chinese cabbage in 5 kg-capacity plastic bags for sale in wholesale markets. However, for supermarkets, the produce (1-2 heads) is packed in perforated plastic bags (with 4-8 holes, 5 mm diameter) or individually wrapped with PVC film. For Chinese kale, the harvested produce is brought to the packing shed for trimming of damaged leaves and packing in 5 kg-capacity plastic bags. The produce in bags is transported by truck to wholesale markets. In supermarkets, Chinese kale is cleaned and repacked in perforated plastic bags. Controlling yellowing Yellowing in leafy vegetables is undesirable. Leaf yellowing may be related to genetics (i.e. cultivars), exposure to abusive temperatures, exposure to exogenous ethylene, and the level of stress tolerance inherent in the leaf tissue. Five possible strategies can be used to reduce yellowing: 1) breeding


for improved resistance to yellowing, 2) improved handling and transport system that would provide good temperature control, 3) segregation from or control of exogenous ethylene, 4) increased tolerance to abusive temperatures, and 5) control of ethylene response. Leaf yellowing is a serious problem in Chinese kale but not so in common cabbage and Chinese cabbage. Precooling (hydrocooling at 4oC for 5-10 minutes) has been shown to minimize the problem. If proper precooling and temperature control can be maintained during handling, transport and distribution, leaf yellowing will not be a problem. In addition, produce should be protected from exposure to ethylene. This can be done by separating leafy vegetables from high ethylene-producing products, such as ripening climacteric fruits (e.g. banana, mango, or tomato). Good air exchange and air flow through the mass of the stored produce will help prevent ethylene accumulation.

Implications for Development Cooperation The increasing sophistication of the production and distribution system Southeast Asia coupled with the realities of globalization and trade liberalization will in time increase the demand for appropriate technologies and qualified people to work at all levels in the distribution chain. Through postharvest networks and activities like the present workshop, participants can exchange knowledge and experiences and develop collective efforts to advance the productivity and competitiveness of vegetable industries in countries of the Greater Mekong Subregion and Southeast Asia.


Postharvest Technologies for Fresh Leafy Vegetables

Antonio L. Acedo Jr., Ph.D.

Regional Project Coordinator, AVRDC-ADB Postharvest Projects RETA 6208/6376

AVRDC-ADB Postharvest Project Office, P.O. Box 3938, Vientiane, Lao PDR

Introduction Leafy vegetables are important crops in GMS countries, providing income to many small farmers, processors and other entrepreneurs, and serving as health foods for the rural and urban populace. They are rich sources of vitamins, minerals, and dietary fiber. Leafy vegetables also have a vital role in the global drive to end hidden hunger, i.e. micronutrient deficiency (Buyckx, undated). Deficiency in vitamin A is a major problem in 37 countries, mostly in Southeast Asia and Africa, with 250,000-500,000 people, mostly children, becoming partially or totally blind yearly. Also, more than 2 billion people worldwide are anemic or have insufficient iron intake. Green leafy vegetables are rich in both vitamin A and iron. Sustainable and reliable food supply systems can ensure global food availability, access to food at the household level, and more opportunities for development of people’s well-being. A vital strategy is to reduce postharvest losses, especially fresh leafy vegetables, which are highly perishable. Reducing postharvest losses would not only increase food availability to the growing world population but also decrease the area needed for production and conserve natural resources (Kader, 2006). There are many postharvest technologies that extend the marketable life of fresh vegetables, but the appropriateness of these technologies has to be ascertained through site-specific and commodity-specific studies. A technology used elsewhere is not necessarily the best for use under conditions of a given developing country. Technologies developed in a developing country are simpler and less costly and may suit better the need of another developing country than modern technologies in developed countries. In recent years, reducing postharvest losses has become part of the effort to improve food availability; the other part is placed on assuring quality and safety of fresh produce. This is due to a shift in market demand in response to consumers' rising nutritional expectations and food safety awareness. Success in the marketplace for fresh produce could be highly correlated with


maintaining product quality and safety (Sullivan et al., 1991). Countries can therefore increase their competitiveness and world market shares by providing higher quality, safe products and promoting lower prices through technological innovations. This paper focuses on postharvest technologies that can be adapted to Cambodia, Laos, and Vietnam. It also reviews other techniques and information that can be considered in future initiatives. In addition, sample cost-benefit analysis of selected techniques is introduced in preparation for the training on this topic next year and for similar analysis to be done for the techniques developed in the AVRDC-ADB postharvest projects. Leafy vegetables given emphasis in this paper include the leafy brassicas, such as common cabbage. which is also known as round cabbage or head cabbage (Brassica oleracea var. capitata), Chinese cabbage (Brassica rapa. var. pekinensis), bok choy or pak choi (Brassica rapa. var. chinensis), which is a non-heading form of Chinese cabbage, Chinese mustard (Brassica juncea var. rugosa) and other priority vegetables of country partners (e.g. amaranth, kangkong).

Quality of Leafy Vegetables Leafy vegetable quality is mainly based on appearance (e.g. fresh-looking, well-formed or well-shaped, right size, right maturity, right color, turgid or not wilted, free of defects such as rot, physical damage, yellowing, or wilting) and to a certain extent, other attributes that cannot be seen but can be felt by the other human senses, such as firmness, tenderness, and taste. For common cabbage and Chinese cabbage, the heads should be light green, compact but not overmature (no seed stalk), right size, and free of defects. Freshness of cabbages can be tested by rubbing two heads together; if they are fresh, they will make a squeaking sound. For other leafy vegetables, consumers look for similar visual quality attributes (freshness, uniformity of size, shape and typical color, and free of defects). In addition, in Chinese mustard, the produce should have the typical flavor or aroma. Concerns about food safety and nutritional value have made quality definition more complex. Safety factors include pesticide residues (the most important safety issue among consumers), microbial contamination (the number one safety concern among health authorities and scientists), natural toxicants (e.g. antinutrients), natural contaminants (e.g. mycotoxins, bacterial toxins and heavy metals such as cadmium, lead, mercury), and environmental pollutants (Kader and Rolle, 2004). These safety concerns, particularly microbial


contamination, are the basis for the worldwide promotion of safety standards in production (e.g. Good Agricultural Practices or GAP), postharvest handling (e.g. Good Hygienic Practices or GHP) and processing (e.g. Good Manufacturing Practices or GMP) which incorporate principles and recommendations in HACCP and Codex Alimentarius.

Produce Quality Deterioration and Postharvest Losses

Main causes of quality deterioration and postharvest loss of leafy vegetables are wilting, yellowing, mechanical injury, high respiration rate, and decay (Kitinoja and Kader, 2003). These loss factors can be categorized into physiological, pathological, and mechanical causes. Physiological deterioration Water loss and leaf wilting. Leafy vegetables are mostly water (>90%) and have the propensity to lose water through transpiration (evaporation of water from plant tissues). Water loss is the main cause of weight loss (loss in saleable weight) and wilting (Fig. 1). It also induces degradation of nutritional components (e.g. vitamin C loss) and imposes stress (i.e. water stress) that increases respiration and ethylene production. In pak choi, postharvest wilting is primarily due to water loss through the stomata (O’Hare et al., 2001). Water loss has been measured at 2.8% per hour when held at 35°C. Complete closure of all stomata occurs between 10-15% moisture loss. Wilting occurred more rapidly in leaves with lower initial water potential. Water potential in pak choi was highest when harvested at 0400 and 2200h. Respiration and ethylene production. Leafy vegetables are non-climacteric, i.e. they do not exhibit a final surge in respiration and ethylene production during the final phase of senescence (Jobling, undated). Cabbages generally have lower respiration and ethylene production rates due partly to their morphology, in which the young inner leaves are fully covered by the more mature outer leaves, as compared to Chinese kale, mustard greens, and culinary herbs. However, they are sensitive to ethylene (senescence hormone), which causes yellowing, epinasty (leaf curving), and abscission (Fig. 1) (Cantwell and Reid, 2006; Cantwell and Suslow, 2006; Jobling, undated). In lettuce, ethylene induces russet spotting, manifested as dark brown spotting of the midribs.


A. Ethylene-induced disorders B. Bacterial soft rot, wilting and yellowing

Figure 1. Ethylene-induced cabbage yellowing and culinary herbs epinasty, abscission, and yellowing (Cantwell and Reid, 2006; Cantwell and Suslow, 2006); bacterial soft rot in common cabbage and Chinese

cabbage; and out leaf wilting and yellowing in Chinese cabbage (Acedo et al., 1999; Acedo et al., 2003).

.

Figure 2. Chilling injury development in sweet basil leaves (Cantwell &

Reid, 2006). (Score: 0-no injury, 8-severe. Score of 3 is the limit of commercial acceptability.)

Chilling injury score

Days of storage


Prolonged exposure to ethylene, as low as 0.01 ppm, could cause significant losses of the fresh produce. Ethylene can easily accumulate in packages, packinghouses, storage areas and even markets. All plant tissues produce ethylene, although at varying degrees. In markets (wholesale, retail, distribution centers), the main sources of ethylene, in addition to fresh produce, include ripening fruits, decaying produce, and exhaust gases of vehicles; the concentration could reach 0.02-0.06 ppm, which can cause a 10-30% loss in shelf life of fresh produce (Wills et al., 2000). The effect of ethylene is cumulative, so continuous exposure to a low concentration of ethylene throughout marketing can cause significant harm. The loss of shelf life will be most frustrating for the final consumer as the loss of quality will not be obvious during marketing and retail sale. Aside from accelerating aging of produce, ethylene increases the susceptibility to decay. In pak choi, leaf yellowing was found to be controlled by the sugar level (the main energy substrate) rather than ethylene, which explains the poor performance of anti-ethylene agents (e.g. 1-methylcyclopropene) in extending shelf life (O’Hare et al., 2001). Understanding this mechanism also avoided the potentially expensive error of designing genetically modified pak choi through manipulation of ethylene metabolism. Sugars tend to be highest in younger leaves and lowest in leaves towards the base of the stem even though the leaves may look similar in size and appearance. As a result, shelf life was longer in younger leaves than older leaves. Physiological disorders. Chilling injury is induced by storage below the recommended low temperature requirement but above the freezing point of tissues usually between -2°C to 0°C. In Chinese cabbage, chilling sensitivity varies with cultivar and injuries show as midrib discoloration, especially on outer leaves (Cantwell and Suslow, 2006). Chinese cabbage developed patchy papery necrosis more severely at 0°C and 2°C, while none was noted at 20°C. For tropical leafy vegetables such as kangkong and some mustard greens, chilling injury is induced at 10°C and lower. This was shown in sweet basil leaves, which developed chilling injury symptoms (browning of leaves and growing tip, bronzing of leaf veins, and loss of glossy appearance of leaves) more rapidly at lower chilling temperatures (Fig. 2) (Cantwell and Reid, 2006). For common cabbage, physiological deterioration during storage is associated with stem or seed stalk growth (bolting), root growth, internal breakdown, leaf abscission, discoloration, and black speck (Cantwell and Suslow, 2006).


Pathological decay Bacterial soft rot is the major disease problem in many leafy vegetables, particularly the brassicas (Fig. 1). It is caused by various bacterial species including Erwinia, Pseudomonas, and Xanthomonas and is characterized by slimy breakdown of infected tissue with offensive foul odor. The disease usually develops at the cut portion (butt end) and injured leaves of cabbages. Other common decays in cabbage are watery soft rot (Sclerotinia), gray mold rot (Botrytis cinerea) and alternaria leaf spot (Alternaria spp.) (Cantwell and Suslow, 2006). Mechanical injury

Leafy vegetables are very susceptible to mechanical injury (physical injury/damage). Forms of mechanical injury include leaf tearing, midrib breakage, and leaf or head cracking and crushing. Physical injuries increase the rate of physiological deterioration, including browning, as a result of oxidation of phenolics substances and the susceptibility to decay. Postharvest rots have been found to be more prevalent in bruised or otherwise damaged produce (Bachmann and Earles, 2000). Mechanical damage also increases moisture loss by as much as 3-4 times.

Postharvest losses Physiological, mechanical and/or pathological deterioration in quality results in partial or total loss of fresh produce. It is caused by a number of interacting factors, which may be preharvest, harvest, and/or postharvest in origin, such as poor crop variety, unfavorable climate, inadequate cultural practices, lack of harvesting techniques, improper handling, and poor storage conditions. Non-technological factors also contribute to postharvest loss, such as lack of capable human resources, lack of knowledge of technical and scientific technologies, inefficient commercialization and marketing systems, lack of logistics support, and lack of enabling policy for the use and administration of human, economic, technical, and scientific resources. Postharvest losses of leafy vegetables vary with commodity, location, growing season and other factors such as standards of quality and consumer preferences and purchasing power, which differ greatly among countries and across cultures (Kader and Rolle, 2004). Postharvest loss estimates in developing countries are alarming (e.g. 20-50% of production) but efforts are lacking to specify the seriousness of the problem and the interventions that are really needed.


In the AVRDC-ADB postharvest projects, postharvest losses were determined at specific stages in the supply chain in Cambodia, Laos and Vietnam and outright volume loss of specific vegetables including the leafy types (e.g. Chinese cabbage) was estimated at an average of 17% (Weinberger et al., 2007). The loss situation maybe more serious if qualitative losses (e.g. loss in price due to reduced quality, loss in nutritional quality, edibility or caloric value) were factored in. Contributing factors to these losses were identified and prioritized for R&D interventions. In the present RETA 6376 initiative, more specific assessment of postharvest loss is being pursued, covering selected leafy vegetables in two upland areas of each CLV country at the farmer and processor levels.

Achieving Desired Quality and Reducing Postharvest Losses The farm-to-table approach (other terms: system approach, whole chain approach, supply chain approach) is increasingly used to produce and deliver agricultural produce, particularly perishable crops such as leafy vegetables. Production ventures have become more consumer-driven than supply-driven as consumers are now more health-conscious and aware of product quality and safety. Previously, the main concern of vegetable crops research was to increase yield, while quality was based only on appearance and taste. This situation has changed and more attention is given to the nutritional and microbiological quality. Obtaining desired product quality and reducing postharvest loss can be achieved by using appropriate crop variety and proper conditions and techniques during production, harvesting, and postharvest handling. The following technological recommendations and innovations focus on postharvest handling, the final stage in the process of producing quality and safe products for consumers. Maintaining a level of freshness from the field to the table has many challenges which when met could expand market opportunities and competitiveness.

Improved crop variety Leafy vegetables have limited storage life even under optimum storage conditions. The potential storage life is partly under genetic control and can be manipulated by breeding. Breeding for long shelf life and desired shipping quality is needed most in developing countries with hot and humid climates where refrigerated facilities are lacking due to high initial and operational cost.


More efforts are now exerted to develop varieties with long shelf life, desired shipping and processing attributes, and high levels of nutrients, in addition to developing tropical (high temperature-resistant) varieties of otherwise temperate or semi-temperate vegetables such as the brassicas (e.g. cabbage, Chinese cabbage). Breeding leafy vegetables with high carotenoids content has been reported and results in lettuce proved to be promising due to observed genetic variations in B-carotene and lutein contents (Fonseca, 2004). B-carotene and lutein contents were further observed to be higher in leaves with higher chlorophyll content. Other nutrients in vegetables include those with therapeutic or pharmaceutical use, hence the term nutraceuticals. A growing concern is placed on the possibility of accidentally lowering beneficial non-target components while enhancing target phytochemicals with new technologies. Production conditions and techniques Environmental conditions and cultural practices during production have a tremendous effect on produce quality, safety, and shelf life. For example, lettuce harvested during a period of rain does not ship well and product losses are increased. Produce that has been stressed by too much or too little water (by irrigation or rainfall), high rates of nitrogen fertilization, or mechanical injury (scrapes, bruises, abrasions) is particularly susceptible to postharvest diseases. Brassicas are susceptible to bacterial soft rot if nitrogen is applied as foliar feed, thus nitrogen should be applied to the soil. This was not observed in pak choi (Jiang and Pearce, 2005). Applying nitrogen above the optimal rates did not result in reduced shelf life, while spraying nutrient solution appeared to be beneficial as it retarded yellowing. Potassium sulfate application also enhanced chlorophyll content and extended shelf life of pak choi. Stress during growth has different effects on produce quality and shelf life. Sustained and intermittent water stress had mostly negative effects for pak choi (Jiang and Pearce, 2005). Although shelf life of pak choi could be extended by these stresses, the plant fresh and dry weights were reduced. In Chinese cabbage, water stress did not affect the water content and weight loss during 9-week storage at 0°C. On the other hand, low light stress (shading) before harvest resulted in more rapid yellowing and wilting in pak choi. It also lowered the leaf sugar, organic acids and chlorophyll contents. Increasing the period of shading before harvest further reduced sugar content and increased moisture loss during storage.


Ensuring safety of fresh leafy vegetables also begins in the field. Outbreaks of food-borne illnesses have been traced to contamination of produce in the field (Bachmann and Earles, 2000). Some preventive measures include (1) avoiding application of fresh animal manure or slurries to a field or to an area immediately adjacent to a field nearing harvest maturity, (2) cleaning equipment that has been used to apply manure on one field before moving it to another field, (3) avoiding using irrigation water from a farm pond used by livestock, and (4) avoiding contact of produce with soil during growth (this can be done by mulching) or harvest.

Proper harvesting and field handling Quality cannot be improved after harvest, only maintained; therefore it is important to harvest at the proper maturity stage and at peak quality. Immature or overmature produce may not last as long in storage as produce picked at proper maturity. Common cabbage and Chinese cabbage heads are harvested when firm and mature (Bautista and Acedo, 1987; Boyette et al., 1992; Stephens, 2003; Cantwell and Suslow, 2006). Compactness (firmness, hardness, solidity) of heads may be determined by hand pressure. A compact head can be only slightly compressed with moderate hand pressure. Delaying harvest even a few days beyond maturity can result in split or cracked heads and increased incidence of rot. Immature heads are puffy or have hollow spaces because the inner leaves are not fully developed and hence, loosely arranged, which make them susceptible to damage (Bautista and Acedo, 1987). When harvested immature, yield also decreases and shelf life is shorter than that of mature heads. Harvest maturity of other vegetables such as leafy mustards, amaranth and kangkong is based on tenderness of leaves, plant size and number of days after planting (usually 25-30 days). They are harvested when they have developed to the fullest size, yet not so advanced in age that the leaves are tough and the flavor is bitter. Physiological age of the vegetable or the leaves within a plant could affect the rate of postharvest quality loss. In pak choi, young leaves (20-25 days after emergence) are more prone to moisture loss and subsequent wilting than older ones (40 days) (O’Hare et al., 2001). However, older leaves turned yellow more quickly than younger leaves. This response was related to initial sugar content, which was higher in younger leaves. In Chinese cabbage heads, mature leaves had a greater tendency to yellow than the same leaves, but detached from the head. Young leaves in intact heads began to swell and expand after one month of storage, causing some heads to crack; cracking was followed by rapid senescence of whole heads.


The time of the day when harvesting is done also affects produce quality and shelf life. In general, harvesting during the coolest time of the day is desirable because the produce would not be exposed to the heat of the sun and the efficiency of the harvesters would be high. If harvesting during the hotter part of the day could not be avoided, the harvested produce should be kept shaded in the field to minimize weight loss and product heat. Handle produce gently during harvesting and field handling. Research showed that harvest time of day could affect quality of pak choi but not Chinese cabbage. Pak choi harvested at 0400h and 2000h contained the highest initial and final water contents. Leaves harvested at these times maintained highest water potential, resulting in a slower rate of wilting than those with lower water potential (Jiang and Pearce, 2005). However, harvesting later in the day has an added advantage, as sugar levels were found to be higher as a result of photosynthesis during the day (O’Hare et al., 2001). This could slow down leaf yellowing in pak choi, which has been associated with sugar depletion. Harvesting is done manually, hence the harvesters have a major influence on produce quality. They should be made aware of the importance of good sanitation practices, be properly instructed in selecting for maturity, and be cautioned against handling produce roughly. An experienced picker should be able to determine the level of maturity quickly and consistently. A cabbage head is harvested by bending it to one side and cutting it with a knife which should be sharpened frequently to reduce effort and lessen picker fatigue. The head should not be removed by snapping or twisting, as this practice damages the head and results in inconsistent stalk length and trim. Broken stalks are also more susceptible to decay. The stalk should be cut flat and as close to the head as possible, yet long enough to retain two to four wrapper leaves. Extra leaves act as cushions during handling and may be desired in certain markets. Yellowed, damaged, or diseased wrapper leaves should be removed. Heads with insect damage and other defects should be discarded. It is essential that heads not harvested be left undamaged because fields may be harvested as many as three times for maximum yield. Harvested cabbage can be placed in bags, boxes, wagons, or pallet bins. Harvesting aids can significantly reduce labor costs, improve harvest efficiency and cabbage quality, and speed the harvest operation dramatically. Aids may be as simple as a modified farm trailer for transporting and boxes. Throwing of harvested cabbages to the container or collection vehicle should be avoided; instead, have someone catch the head for proper placement to prevent physical injuries. If labor is scarce, a conveyer can be used to load the harvest into the collection medium. Conveyors reduce harvest cost and speed


harvest. Mustard greens and kale may be harvested as single leaves or as whole plants. Fields are usually harvested several times, but care must be exercised to prevent damage to the plants. After harvest, purposive water loss (2-3% water loss) may be imposed. In pak choi, this can be done by laying plants under the sun for 30 minutes right after harvest (Jiang and Pearce, 2005). This was found to significantly reduce mechanical damage (snapping of turgid outer leaves) when the produce was packed into bamboo baskets. Subsequent washing to remove dirt was able to re-hydrate the produce. Wilted pak choi could be re-hydrated (and cooled) by dipping in water and the general appearance, color and original weight could be restored if moisture loss was less than 10% Re-hydration and controlled water loss led to a reduction in losses of 14.5%. The practice in Cambodia of leaving cabbage heads in the field for an hour or two with the cut butt end exposed to the sun may also work for the above purpose (Vanndy and Buntong, 2007). Additionally, this practice would dry out the cut butt end of the cabbage head, thereby depriving soft rot pathogens of water needed for their growth and development. However, the problem of heat accumulation within the produce has to be addressed. After the treatment, prompt transport to the packing shed should be done to dissipate field heat without the use of water for cooling. Washing is not advisable in common cabbage. Other leafy vegetables should be transported to the packing shed as soon as possible as they are particularly susceptible to wilting and other damage from high temperatures.

Packinghouse techniques Trimming. Leaves that have yellowed, show signs of disease, or have other obvious defects should be discarded. Removal of the four outer leaves of pak choi heads increased shelf life to over 14 days (Jiang and Pearce, 2005). In Chinese cabbage, farmers may remove all the outer leaves before transport to market. This is a traditional practice of some Chinese farmers, in which the outer nine leaves of Chinese cabbage are removed at harvest. A second trim of three leaves is made to remove mechanically damaged leaves following transport. A simple change of this practice by removing only six leaves at harvest and leaving the other three outer leaves to protect the head from physical injury was found to reduce losses by 22% without any decline in product quality, and increased the profits of the farmers. In common cabbage, outer leaves (wrapper leaves) also are trimmed off except for 3-4 wrapper leaves to protect the head from injuries during handling and transport (Bautista and Acedo, 1987). However, wrapper leaves could not fully protect the head from too much force due to impact or compression, which usually results in head bursting. Due care during handling is important.


Sorting/Grading. Systematic sorting/grading coupled with appropriate packaging and storage will extend postharvest shelf life, wholesomeness, freshness, and quality, and will substantially reduce losses and marketing cost. Sorting is done to separate poor produce from good produce, and further classify the good produce based on other quality parameters, such size (Bautista and Acedo, 1987). If this is done following quality standards set by product standards agencies or industry requirements, the process is referred to as grading. Leafy vegetables are usually sorted/graded based on maturity, size, shape, color, weight, and freedom from defects such as insect, disease, and mechanical damage. In developing countries, implementation of grade standards as well as safety standards for leafy vegetables and other fresh horticultural produce faces formidable difficulties that contribute to the lingering problem of high postharvest losses. Grade standards, if enforced properly, are essential tools of quality assurance during marketing. They provide a common language for trade among farmers, handlers, processors, and marketers, maintain orderly marketing and equity in the market-place, and protect consumers from inedible and poor quality produce (Kader, 2006). Washing and sanitizing. Most leafy vegetables are washed in clean water to remove dirt and other debris and surface contaminants. This is especially important during rainy weather as the produce is often contaminated with soil. In heading type of cabbages, washing is not advisable since it could favor bacterial soft rot if the cabbages are not properly dried. The inner edible part is kept clean by the wrapper leaves. Sanitation is essential to control the spread of diseases from one item to another and to limit the pathogen load in wash water or in the packinghouse air. Waterborne microorganisms, including postharvest plant pathogens and agents of human illness, can be acquired rapidly and taken up on plant surfaces (Kader, 2006). Natural plant surface contours, natural openings, harvest and trimming wounds can be points of entry and provide safe harbor for microbes. Chlorine in the form of sodium hypochlorite (NaOCl) solution (e.g. Clorox or commercial bleach) or as dry, powdered calcium hypochlorite can be used in wash water as a disinfectant. For the majority of vegetables, chlorine in wash water should be maintained in the range of 75-150 ppm (Suslow, 1997; Bachmann and Earles, 2000). The antimicrobial form, hypochlorous acid, is most available in water with a neutral pH (6.5 to 7.5). Concentrations above 200 ppm may injure some vegetables (e.g. leafy greens and celery) or leave


undesirable off-flavors. A 100 ppm chlorine solution can be prepared by mixing four tablespoons of commercial bleach (5.25% NaOCl) per gallon of water (Bautista and Acedo, 1987). Chlorine is used routinely as a sanitizer in wash, spray, and flume waters in the fresh fruit and vegetable industry (Beuchat and Ryu, 1997). Antimicrobial activity depends on the amount of free available chlorine (as hypochlorous acid) in water that contacts microbial cells. Chlorinated water also can be used during hydrocooling and to disinfect packinghouse, packaging, and transport facilities. Furthermore, use of sanitized wash water can help to prevent postharvest diseases and food-borne illnesses. E. coli 0157:H7, Salmonella, Cryptosporidium, Hepatitis, and Cyclospora are among the disease-causing organisms that have been transferred via fresh fruits and vegetables. A standard procedure for washing lettuce leaves in tap water was reported to remove 92.4% of the microflora (Adams et al., 1989). Including 100 ppm available free chlorine in wash water reduced the count by 97.8%. Adjusting the pH from 9 to 4.5-5.0 with inorganic and organic acids resulted in a 1.5- to 4.0-fold increase in microbicidal effect. Increasing the washing time in hypochlorite solution from 5 to 30 minutes did not decrease microbial levels further, whereas extended washing in tap water produced a reduction comparable to hypochlorite. The addition of 100 ppm of a surfactant (Tween 80) to a hypochlorite washing solution enhanced lethality but adversely affected sensory qualities of lettuce. Ozone as a sanitizer may not be practical in developing countries because of the high cost of generation and application. Hydrogen peroxide (food grade) also can be used as a disinfectant. Concentrations of 0.5% or less are effective for inhibiting development of postharvest decay caused by a number of fungi (Bachmann and Earles, 2000). Hydrogen peroxide has a low toxicity rating and is recognized as having little potential for environmental damage. Other commodity treatments. Anti-bacterial treatments can be applied to common cabbage and Chinese cabbage to control bacterial soft rot. The use of saturated alum solution and lime paste has been found very effective in controlling soft rot in common cabbage (Bautista and Acedo, 1987). Alum has two-fold functions to control bacterial soft rot: as an antimicrobial agent by direct kill, and as a moisture-withdrawing substance that deprives the bacterial pathogens of water. However, alum is phytotoxic and causes black spotting on affected leaf tissues, thus care must be taken to apply alum only on the butt end of cabbage. The use of alum is now a commercial practice of common cabbage growers in the Philippines.


Lime is only moisture-withdrawing, and usually cannot control soft rot if the pathogen already has entered into the tissues through wounds. Lime paste is commercially used by common cabbage growers in Indonesia and Chinese cabbage packinghouses in Thailand. Other simple, low-cost techniques to control bacterial soft rot in both cabbages have been developed, including the use of botanicals or leaf extracts from plants that are known to be edible or consumed as medicinal plants. One effective treatment is the use of guava leaf extract, the effect of which in common cabbage and Chinese cabbage was comparable to alum treatment (Acedo et al., 1999, 2003; Acedo and Capuno, 2004). Cabbages treated with guava leaf extract were free of bacterial soft rot while untreated heads all developed soft rot symptoms after pathogen inoculation, resulting in trimming losses of more than 30%. Other plants known to be edible or medicinal, such as oregano, milkweed (medicinal plant used to contain dengue fever), and lemon grass, were less effective. After treatment, the applied extract or substance (alum or lime) requires proper drying before packing. Proper packaging Proper packing is essential to maintaining the freshness of leafy vegetables. Packaging should be designed to prevent premature deterioration of product quality, in addition to serving as a handling unit (Bautista and Acedo, 1987). As protection, packages should prevent or reduce physical injury to the produce during transit and handling, provide ventilation to hasten cooling and escape of heat caused by respiration, and reduce water loss from the produce (Gast, 1991). Some packages promote sale of the produce. Produce packages. Rigid containers (e.g. plastic or wooden crates, cartons) are far better than non-rigid containers (e.g. mesh bags, plastic bags) to protect produce from damage during handling and transport. Rigid packages are also easier to palletize. The different packages are described as follows:

Basket: Usually refers to containers made of woven materials such as bamboo, rattan, or plastic strips. Box: Usually refers to containers made of corrugated fiberboard or Styrofoam. It may be a two-piece telescoping box, or a carton that closes with top flaps. The contents can be place-packed with liners and layer dividers, or bulk-filled. Crate: Usually refers to a wooden or plastic container. Wooden crates are usually wirebound and may be collapsible.


Plastic containers, a relatively new type of container, have good stacking strength and are water resistant. The use of plastic crates for handling and transportation of vegetables was introduced recently in some developing countries. In Nepal, the use of plastic crates is increasing among farmers and traders, particularly in situations where their return and reuse can be guaranteed; the crates have been reported to reduce postharvest losses and improve quality and safety of vegetables (Adhikari, 2006). In Sri Lanka, losses of vegetables were reduced from 30% with the use of poly sacks to 5% with the use of plastic crates (Fernando, 2006). Reinforcing and handling packages. Telescoping construction, dividers and corner reinforcement are ways that boxes have been made stronger. Container liners and cushions minimize physical injuries. Containers need to be vented to lower and maintain produce temperature for storage (Gast, 1991). Vents allow cold air to be forced more quickly through the containers and produce. Vents also allow the heat built up by respiration to escape. Produce exposed to high temperatures in unvented containers will usually have a shorter shelf life. A well-made container has uniform venting, so when it is stacked the vents will match other containers. Matching is important so cold air can be pulled through a whole stack of containers. Too much venting weakens a container, while too little venting restricts the air flow through it. A good rule of thumb is to have 5% of the container sides and/or ends vented. A few large vertical vents are better than many small round ones. A container with liners and vertical dividers will eliminate the beneficial effects of vents. An alternative way is to wrap the produce individually. Wrapping produce reduces vibration and impact damage. Old newsprint and brown paper can be used as wrapping materials. Some vegetables such as mustard greens and kale may be bundled before wrapping and packing. Palletization or unitized handling (stacking containers on standard size pallets) is used to reduce the number of times an individual container is handled, and to reduce damage to the contents. Container sizes should fit standard pallet sizes. Modified atmosphere packaging (MAP). MAP is very effective in retaining freshness, and for extending the shelf life of fresh produce by maintaining the green color of leafy vegetables, reducing loss due to the production of respiratory heat by produce, maintaining the natural fresh taste of produce, and as a result, extending product shelf life.


MAP is exemplified by the use of polymeric films as packing material. Low density polyethylene film is generally used for the packaging of fresh fruits and vegetables, owing to its high permeability and softness when compared to high density film (Somjate, 2006). Polyethylene can be sealed easily, has good O2 and CO2 permeability, low temperature durability, good tear resistance and good appearance. This film is therefore used for the production of MAP, which can be manipulated to match the characteristic respiration of produce by reducing O2 levels to slow down the rates of respiration and senescence of the produce. However, plastic films of high-density polyethylene also were found to markedly reduce water loss of produce (Ben Yehoshua, 1978). Because polyethylene bags are non-rigid material, the volume of vegetables to be packed should be limited. In a study on packing 5, 10 and 15 kg Chinese kale in each polyethylene bag, it was found that losses due to weight loss, bruising and trimming increased with increasing product volume and were about 5.6%, 6.9%, and 13.1%, respectively (Amuttiratana and Passornsiri, 1992). Plastic film packaging in pak choi effectively reduced moisture loss and wilting and was considerably more effective than manual misting or treating leaves with anti-transpirant chemicals (O’Hare et al., 2001). Plastic packaging maintains high relative humidity, which necessitates sanitary washing before packing to avoid bacterial rot. In another MAP trial under supermarket conditions (ambient 28°C) using plastic film wrap (clingwrap), it was found that semi-packed pak choi (two-thirds of leaves exposed) performed better than fully packed and non-packed (Jiang and Pearce, 2005). Although the fully packaged produce had less water loss, it tended to have more rot than the other treatments. Supermarkets preferred the semi-pack option from an aesthetic standpoint, as the fully packaged produce tended to fog due to moisture condensation. In Chinese cabbage, plastic film wrap was similarly effective in reducing moisture loss from outer leaves. However, rot develops if the heads are mechanically damaged. Cooling and storage techniques Cooling is the foundation of produce quality protection. It extends shelf life by reducing the rate of physiological change and retarding the growth of spoilage microorganisms. Because every degree of reduction from ambient temperature increases storage life, every form of cooling is beneficial, even if it is not optimum. Simple, low-cost cooling or refreshing the product is better


than no cooling at all. Ways of cooling fresh produce include (1) keeping out of direct sun, (2) using natural cooling, e.g., harvest during the cool early morning hours, open stores for ventilation during the cool of the night, cool temperatures of high altitude or a natural source of cold water when available, (3) evaporative cooling obtained by drawing dry air over a moist surface, (4) mechanical refrigeration, and (5) cooling promptly after harvest by appropriate precooling methods. Some cooling and storage recommendations and simple techniques are described by Kitinoja and Kader (2003). Precooling. Precooling is among the most efficient quality enhancements available to commercial producers and was found to rank as the most essential of the value-added marketing activities (Sullivan et al., 1996). Research confirms that lowering the respiration rate of fresh vegetables is essential to preserving market quality and the most important technology for lowering respiration rates remains proper precooling of produce within hours of harvest. Proper precooling preserves product quality by: (1) inhibiting the growth of decay producing microorganisms, (2) restricting enzymatic and respiratory activity, (3) inhibiting water loss, and (4) reducing ethylene production. There are different precooling methods (Table 1) and among these, forced-air cooling and hydrocooling were found to be the most effective and economical in preserving optimum quality and increasing market life. Hydrocooling by dipping in cold water (water cooled by adding ice) is simple and could be effective in maintaining the freshness of leafy vegetables. Hydrocooled vegetables must, however, be kept cool to prolong their shelf life. Furthermore, leafy vegetables can be sprayed repeatedly with water, especially at destination markets, to maintain low temperatures and to prevent wilting or softening. In developing countries, ice cooling or top icing is used for leafy vegetables due to increasing availability of ice. Ice packing can be used to cool vegetables during transport, distribution and storage. In tropical climates, the temperature in a box of leafy vegetables may increase to 35-40°C when sealed in the afternoon and transported the following morning. Ice packaging can lower the temperature to 20-25°C (Huang, 2006). It was also found effective in reducing leaf yellowing, wilting, and trim loss. For vegetables sensitive to chilling injury or that are damaged when in direct contact with ice, such as amaranth, a layer of newspaper can be placed between the layers of vegetables and ice. The thickness of the alternating layers of vegetables and ice is dependent on the type of vegetable, the ambient temperature, and the distance or the time to the market.


Cabbages can be precooled to 40°F before transport to improve shelf life and reduce rot (Sanders, undated). Rapid cooling either by hydrocooling alone or in combination with package icing is essential to maintaining the quality of leafy greens. In pak choi, ice packing is a cheap form of cooling to extend shelf life but has not been adopted by growers, for two reasons (Jiang and Pearce, 2005). First, growers were seldom in a position to easily access ice. Second, loose ice required plastic packing containers, which would lead to additional cost for growers. Furthermore, the effect of ice is transitory. Without proper insulating material, ice melted quickly, and temperature returned to near ambient. Optimum storage conditions. If produce is to be stored, it is important to begin with a high quality product. Damaged or diseased produce must be separated or discarded and containers must be well ventilated and strong enough to withstand stacking. Damaged produce is going to spoil and induce spoilage in the rest of the crop. In general, proper storage practices include temperature control, relative humidity control, air circulation, and maintenance of space between containers for adequate ventilation, and avoiding incompatible product mixes.


Table 1. Postharvest cooling methods and suitable commodities (Sullivan et al., 1996).

Cooling method

Commodities Comments

Hydrocooling Most leafy vegetables, fruits and fruit-type vegetables, sweet corn, snap beans

Very fast cooling; uniform cooling in bulk if properly used, but may vary extensively in packed shipping containers; daily cleaning and sanitation measures essential; product must tolerate wetting; need water-tolerant shipping containers

Forced-air cooling (pressure cooling)

Most fruits, berries, fruit-type vegetables, tubers, and vegetables not susceptible to chilling injury

Much faster than room cooling; cooling rates very uniform if properly used. Container venting and stacking requirements are critical to effective cooling. Economical and efficient.

Package-icing Most vegetables Fast cooling; limited to commodities that can tolerate water-ice contact; water-tolerant shipping containers are essential. Economical and efficient.

Room cooling All commodities Too slow for many perishable commodities. Cooling rates vary extensively within loads, pallets, and containers.

Vacuum cooling

Leafy vegetables, iceberg lettuce

Commodities must have a favorable surface-to-mass ratio for effective cooling. Causes about 1% weight loss for each 6°C cooled. A procedure that adds water during cooling prevents this weight loss, but equipment is more expensive, and water-tolerant shipping containers are needed.

Transit cooling Mechanical refrigeration

All commodities Cooling in most available equipment is too slow and variable; generally not effective for field heat removal.

Top-icing and channel-icing

Most vegetables Slow and irregular, top-ice weight reduced net payload; water-tolerant shipping containers needed.

Temperature is the most important environmental factor that influences the deterioration of harvested commodities (Kader, 2006). The optimum storage temperature for most temperate or semi-temperate/subtropical leafy


vegetables, such as many brassicas, is close to 0°C while tropical produce, >10°C. Relative humidity (RH) can influence water loss, decay development, and incidence of some physiological disorders. Condensation of moisture on the commodity (sweating) favors decay development. For most leafy vegetables, RH requirement usually ranges from 90-98%. (Kader, 2002; Kader and Rolle, 2004). Optimum temperature is achieved by mechanical refrigeration. In refrigerated chambers, RH can be increased by (1) adding moisture (water mist or spray, steam) to air through humidifiers, (2) regulating air movement and ventilation, (3) maintaining temperature of the refrigeration coils within about 1°C of the air temperature, (4) providing moisture barriers that insulate walls of storage rooms and transit vehicles, or (5) wetting the floor. Semi-temperate leafy vegetables, such as cabbages and some other brassicas, can be stored at 0-2.5°C with 95-98% RH (Boyette et al, 1992; Cantwell and Suslow, 2006; Cantwell and Reid, 2006; Sanders, undated) while for tropical produce (e.g. mustard greens, kangkong), a temperature above 10°C (usually 13°C) is recommended. Higher temperatures accelerate physiological deterioration and quality loss. In lettuce, higher storage temperature (10°C) hastened chlorophyll and carotenoid loss compared with low temperature (4°C); anthocyanin and phenolics contents were unaffected (Ferrante and Maggiore, 2007). Chlorophyll a fluorescence was used to determine the effects of storage time and temperature on lettuce leaf quality. Exposure to alternating cold and warm temperatures may result in moisture accumulation on the surface of produce (sweating), which may hasten decay. Different commodities stored together should be capable of tolerating the same temperature, RH, and level of ethylene in the storage environment. High ethylene producers, such as ripe bananas, apples, cantaloupe, can stimulate undesirable physiological changes in color, flavor, and texture in ethylene sensitive commodities, such as leafy vegetables. A farmer who can cool and store produce has greater market flexibility because the need to market immediately after harvest is eliminated. The challenge, especially for small farmers, is the set-up cost. Evaporative cooling storage. Refrigerated facilities are expensive both in terms of set-up and operational cost. Alternative storage methods are therefore important in developing countries and one of these is evaporative cooling storage. An evaporative cooler developed in India, designated as the Zero Energy Cool Chamber and described as an on-farm, low-cost, environmentally friendly cool chamber, was developed from locally available material (Ahsan, 2006). Temperatures within the chamber were reduced by as


much as 17-18°C, with more than 90% RH during peak summer periods. It increased shelf life and reduced wastage of fruits (banana, mango, oranges, limes, and grapes) and vegetables (tomato and potato). A similar zero-energy storage structure was developed in Nepal (Adhikari, 2006). The structure is constructed using brick and sand, rectangular in shape, and has dimensions of 75 cm x 50 cm x 75 cm. Its outer and inner walls made of bricks are separated by a 10-cm space filled with sand, which is frequently watered to maintain a temperature of 7-10°C and RH of >85%. It increased the storage life and reduced losses of fruits and vegetables, including cabbage and capsicum leafy vegetables. In Sri Lanka, a low cost evaporative cooler also was developed (Fig. 3) and introduced to retail traders (Fernando, 2006). Temperatures inside the cooler are 5-7°C lower than ambient while RH ranges from 90-95%. It has a capacity of 100 kg vegetables and can be used for temporary storage. It reduced losses from 20% to 5%.

Figure 3. Low-cost evaporative cooler developed in Sri Lanka.

(Fernando, 2006) Other simple and low-cost evaporative cooling structures were described previously (Acedo and Thanh, 2006), some of which were tested by partners in Cambodia, Laos, and Vietnam for tomato and chili storage. The box-type evaporative coolers with moist jute sack walling and the other with moist rice hull wall insert, as described in this report, were found to be equally effective in inhibiting wilting and reducing weight loss, resulting in doubling of shelf life of pechay (Brassica napus var. chinensis) (Acedo, 1997). Intermittent exposure to light was found to reduce leafy yellowing, which is a problem of


continuous holding inside the evaporative cooler. Later, postharvest lighting was also found to affect the shelf life of pak choi (Jiang and Pearce, 2005). Leaves stored at 10°C under normal fluorescent lighting had a shelf life of 10 days, compared with 8.2 days for leaves stored in the dark. However, high intensity lighting (metal halide and high-pressure sodium) reduced shelf life to about 6 days due to heat damage. Cold chain. As with refrigerated storage, the cold chain system is not a low-cost technology but is introduced here for future consideration as a joint government-private sector initiative. Cold chain systems preserve the freshness of produce from harvesting through marketing and delivery to the consumer and have a tremendous impact on fresh produce marketing as illustrated by the outcomes in South Korea (Ho, 2006). The economic impact of cold-chain systems is due to (1) increased consumer satisfaction as a result of improved freshness and keeping quality of produce, (2) price stabilization and continuity of supply, (3) reduced total marketing expenses due to reduced product losses, increased net quantities of fresh produce, and reduced unit marketing and garbage disposal costs, and (4) improved quality and competitiveness of farm produce, thereby contributing to increased farmer income. Some developing countries, such as Indonesia and Philippines, are starting to adapt the cold chain approach. In the Philippines, small vegetable growers in different villages of a highland province in Bukidnon (located in the south, in Mindanao) penetrated institutional markets (e.g. fast food chains) in Cebu (in the center, in Visayas) and Manila through clustering and application of the cold chain system (Rapusas, 2006). Previously, selling lettuce to local traders was difficult; prices were low and 25% from the weight was deducted as an allowance for trimmings, despite the fact that the lettuce was of good quality. An alternative market was sought by the grower who began supplying 200 kg of lettuce on a weekly basis to fast food outlets in Cebu, and later, in Manila—the latter requiring air transport of 400 kg lettuce weekly. Apart from the high cost of airfreight, lettuce delivered to the processor did not meet the 61% yield specified in the marketing contract, owing to the need for 16-20% trimming. Attaining the high quality standards of the fast food processor was a formidable challenge to the grower. A further challenge was that of supplying a 20-foot refrigerated van with 3.5 metric tonnes of lettuce on a weekly basis. Clusters of lettuce growers were then formed and shared production technologies and quality standards. With the use of refrigerated transport, the trimmings were significantly reduced to a maximum of 10% and the processor’s yield recovery specification of 61% was successfully met. To further improve the lettuce supply chain, government agencies provided


equipment assistance: a 10-foot refrigerated truck, a 20-foot refrigerated van or container, and a precooler, to complete the cold chain system. Operational steps are as follows: (1) harvested lettuce heads are immediately brought to the packinghouse for cleaning (wiping with a cloth to remove soil and other dirt particles), sorting, air drying (about two hours) and anti-browning treatment (using citrus or ‘calamansi’ juice, alum, or ascorbic acid applied to the cut portion of the lettuce); (2) selected heads are carefully arranged into nestable and vented plastic crates (11.5 kg capacity) with a brown paper lining for every two layers with each layer consisting of 12 heads; (3) cluster growers transport the packed produce to a consolidation area using a rented 20-foot refrigerated van, especially for growers located far from this area; (4) the consolidated packed produce is transported in refrigerated containers to a city pier for loading into the ship en route to Manila (shipping time from the consolidation area up to the buyer/processor takes 40 hours). The achievement of the five-grower lettuce cluster has provided the impetus for other independent, small lettuce growers to join in the cluster. This development has given the cluster a window of opportunity to expand its production volume and, in turn its captive market. Proper transport Minimizing losses during transport/shipment necessitates that special attention be given to vehicles, equipment, infrastructure, and handling. Fresh produce is transported using both refrigerated and non-refrigerated vehicles. Non-refrigerated vehicles generally are open-sided trucks with wire mesh frames. This type of transport is inexpensive and convenient, and is usually used in developing countries. Fresh produce must not be watered prior to loading, as this will lead to decay, rotting, and extensive losses. Major causes of losses during non-refrigerated transport of fresh produce are improper handling during loading and unloading, overloading without separation of produce, which leads to overheating and mechanical injury to produce at the bottom of the stack, rough roads, and lack of ventilation of the produce. Postharvest operations must address these problems. The use of refrigerated transport facilities becomes necessary for fresh produce destined for niche and international markets. For maximum shelf life and quality, green leafy vegetables should not be stored or transported in trucks where there are mixed loads containing ripening fruit such as apples, pears, mangoes, tomatoes, or bananas. Because of their soft and delicate texture, leafy vegetables should be handled gently to minimize mechanical injury. Careful handling is a well-known method of


reducing postharvest losses as is the provision of adequate shipping containers to protect the produce from physical damage. Proper market handling At destination markets, the produce may again undergo cleaning, sorting, packing, and storage. Most postharvest measures described above could be applied at this stage. Ethylene removal from the postharvest chain Ethylene is destructive to quality of fresh leafy vegetables and it accelerates different deteriorative processes. Preventing ethylene buildup around the product in packages and during storage, transport, and marketing is often the simplest method of reducing the damaging effects of ethylene. It is important to avoid storing ethylene-sensitive products such as leafy vegetables with products that produce high levels of ethylene. Increasing the ventilation rate of the storage area is another way of reducing ethylene levels. Ethylene can be removed by several chemical processes. Potassium permanganate usually is used because it reacts with ethylene to produce carbon dioxide and water. To scrub the air efficiently, it is best to spread the potassium permanganate over as large a surface area as possible, either in trays or within highly permeable bags. An ethylene scrubber made of potassium permanganate impregnated onto clay-ash chip (a proprietary Philippine product) has been developed. Ayoub et al. (1987) also tested ethylene-absorbing blankets containing alumina coated with potassium permanganate in two mixed loads of fruits and vegetables in two marine containers shipped from California to South Korea. The total produce lost in the container without ethylene scrubbing was 2645 lbs (out of 16,070 lbs) valued at US $928, which is much higher than the US $160 cost of the ethylene scrubbers. The technical and economic feasibility of preventing ethylene damage was demonstrated in lettuce using an ethylene scrubber (Thompson et al., 1989) and by separating ethylene-generating commodities from ethylene-sensitive ones during transport (Jordan et al., 1987).

Economic Analysis of Postharvest Technologies The development, introduction and use of a technology has economic, environmental, and social impacts (Jiang and Pearce, 2005). Economic impacts usually are changes in profitability due to higher demand and/or


bigger markets, lower costs, higher yields, and/or better quality. Environmental impacts are effects on the natural system, such as reduced waste and pollution or improved environmental quality. Social impacts may include enhanced networking, empowerment of the most disadvantaged groups, recognition of gender contributions, and the development of human and social capital. Environmental and social impacts may be quantified in monetary terms, but in many cases they do not have market values. Some impacts cannot be realized right after an intervention has been developed or introduced; only potential impacts can be evaluated and so, certain assumptions and projections have to be made. For postharvest technologies or technological recommendations introduced, economic impacts are mainly longer shelf life, and better quality and/or lower losses of the produce, which lead to higher profitability. For these techniques, cost-benefit analysis could be performed and from this, the return on investment or the cost/benefit ratio can be estimated. Three examples are given below. Example 1: postharvest technical advice The postharvest intervention was given as simple advice to retain 2-3 wrapper leaves in Chinese cabbage instead of removing all outer leaves as traditionally practiced. The technique reduced losses from 28.5% for the traditional practice to 6.3% for the introduced technique, which resulted to a net profit that far exceeded the additional cost (Table 2). Example 2: postharvest technique from exploratory investigation The use of botanical extracts as alternative to alum for cabbage soft rot control was explored. Experiments were conducted and the most effective treatment (guava leaf extract, 1:1 extract:water ratio) showed complete control of the disease in contrast to 100% infection of untreated heads that resulted to trimming losses of 34.8%. The cost and benefit are only potential. The potential net benefit again far exceeded the cost of the technique (Table 3). Example 3: introduction of better postharvest material The use of plastic crates as packaging material for vegetables was introduced and reduced losses to 5% from 30% in the usual practice of using polyethylene sacks (Fernando, 2006). Cost-benefit analysis is shown in Table 4, which illustrates that using plastic crates can increase profitability.


Table 2. Cost benefit analysis of keeping 2-3 outer leaves of Chinese cabbage during transport compared to removing all outer leaves (modified from Jiang and Pearce, 2005). Particulars Unit Traditional

practice Keeping 2-3 outer leaves

Losses -2nd day % 28.5 6.2 -3rd day % 28.6 6.4 -Average % 28.5 6.3

Weight of Chinese cabbage kg 1000.00 1000.000

(1156.07 kg shipped)

-Wasted kg 285.35 62.00 -Sold kg 714.65 938.00 -Revenues @ 0.60 yuan/kg yuan 428.79 526.80

Cost yuan -Transportation cost yuan 33.00 37.50 -Additional labor (loading etc.) yuan 6.00 6.00 -Total costs yuan 93.00 43.50

Net profit (revenues-total cost) yuan 389.79 519.30

1 USD = 8 Chinese yuan or RMB (Renminbi)

Table 3. Potential cost and benefit of using guava leaf extract and alum for bacterial soft rot control in common cabbage (Acedo et al., 1999).

Particulars No treatment

Guava leaf extract Alum treatment

% Trimming losses due to soft rot

-Trial 1 30.9 0 0 -Trial 2 38.6 0 0 -Average 34.8 0 0

Weight of Chinese cabbage, kg 1000 1000 1000 -Wasted 348 0 0 -Sold 652 1000 1000 -Revenues @ 30 pesos/kg 19,560 30,000 30,000

Cost, pesos - Treatment cost

(materials, labor) 0 100 120

-Trimming cost 150 0 0 -Total costs, pesos 150 100 120

Net profit (revenues-total cost), pesos

19,410

29,900

39, 880

1 USD = 52 Philippine peso (PHP)


Table 4. Cost-benefit analysis of using poly sacks and plastic crates for transporting vegetables from the collecting center, Keppetipola to the central (Manning) market in Colombo, Sri Lanka (Fernando, 2006). Particulars

Poly sacks Plastic crate

1) Capacity per truck load

- Number of units transported 80 bags 125 crates - Average weight of vegetables per unit 50 kg 20 kg - Total capacity 4,000 kg 2,500 kg

2) Unit price of a package LKR 30.00/bag 527.00/crate

3) Lifespan of package 2 journeys 240 journeys 4) Farm-gate purchasing price, LKR 25.00/kg 27.00/kg 5) Transport cost LKR

- Keppettipola to central market LKR 2,500.00 2,500.00 - Return journey LKR 625.00*

6) Handling charges LKR 6.00 6.00 7) Selling price of vegetables LKR 30.00 37.00 Capital cost

-Total cost of packages LKR 2,400.00 65,876.00 Fixed cost

-Depreciation of packages LKR 1,200.00 274.00 Variable

-Total transport cost LKR 2,500.00 3,125.00 -Loading and unloading cost LKR 960.00 1,500.00 -Cost of vegetables LKR 100,000.00 67,500.00

Total cost LKR 104,660.00 72,399.0 Total revenue LKR 120,000.00 92,500.00

Net profit LKR

15,340.00

20,100.00

* Empty crates occupy 1/4 of the total truck capacity. 1 USD= 100 LKR. Losses of vegetables were reduced from 30% with poly sacks to 5% with plastic sacks.

Summary Postharvest technologies are essential for leafy vegetables, most of which are highly perishable and prone to physical and biological damage during handling and marketing. Several simple, low-cost techniques are available and can be given as simple advice or adapted and optimized to suit individual country situations. Some very effective, simple techniques entail little or no cost, but adoption has been slow. Technology developers, extension workers, government, and the private sector must encourage greater adoption to achieve the ultimate goal of development efforts.


References

Acedo, A.L. Jr. 1997. Storage life of vegetables in simple evaporative coolers. Tropical Science 37:169-175.

Acedo, A.L. Jr., Acedo, J.Z. and Evangelio, M.F. 1999. Biocontrol of cabbage soft rot using botanical extracts. Research Project Report, Postharvest Technology Laboratory, Department of Horticulture, Visayas State College of Agriculture, Baybay, Leyte, Philippines.

Acedo, A.L. Jr. and Capuno, C.F. 2004. Bio-physical control of postharvest quality deterioration of Chinese cabbage (Brassica oleraceae var. pekinensis). Research Project Report, Postharvest Technology Laboratory, Department of Horticulture, Leyte State University, Baybay, Leyte, Philippines.

Acedo, A.L. Jr., Piol, J.C., Piano, M.R., Bartolini, M.V., Florentino, J.N., Lapeceros, C.M. and Mascarinas, B.E. 2003. Inhibition of Rotting and Wilting of Chinese Cabbage Using Simple and Safe Techniques. Research Project Report, Postharvest Technology Laboratory, Department of Horticulture, Leyte State University, Baybay, Leyte, Philippines.

Acedo, A.L. Jr. and Thanh, C.D. 2006. Postharvest technology of fresh tomato. In: Training-workshop Manual on RETA 6208 Postharvest Technology Training and Development of Training Master Plan, 17-20 October 2006, Vientiane, Lao PDR.

Adams MR, Hartley AD, Cox LJ. 1989. Factors affecting the efficiency of washing procedures used in the production of prepared salads. Food Microbiology 6:69-77.

Adhikari, S. 2006. Country paper: Nepal (2). In: APO. 2006. Postharvest Management of Fruit and Vegetables in the Asia-Pacific Region. Asian Productivity Organization (APO) and FAO. pp. 200-208.

Ahsan, H, S. 2006. Country paper: India (1). In: APO. 2006. Postharvest Management of Fruit and Vegetables in the Asia-Pacific Region. Asian Productivity Organization (APO) and FAO. pp. 131-142.

Amuttiratana, D. and W. Passornsiri. 1992. In: Bhatti, M.H., Hafeez, Ch., A., Jaggar, A. and Farooq Ch., M. (eds.). Post harvest losses of vegetables. Workshop Report, 17-22 October 1992. Pakistan Agricultural Research Council. Islamabad, Pakistan. Food and Agriculture Organization of the United Nations, Regional Cooperation for Vegetable Research and Development RAS/89/41.

Ayoub, J. A.; Driver, M. G.; Kim, H.; Barrett, A. and Taub, I. A. 1987. Use of ethylene absorbers in extending produce shelf life. Report of the Food Engineering Directorate, U.S. Army Natick Research Center, Natick, MA.

Bachmann, J. and Earles, R. 2000. Postharvest handling of fruits and vegetables. Appropriate Technology Transfer for Rural Areas Horticulture Technical Note 800-346-9140. 19 pp. http://www.attra.org/attrapub/postharvest.html

Bautista, O.K. and Acedo, A.L. Jr. Postharvest handling of fruits and vegetables. Manila: National Book Store Inc. Techguide Series No. 4. 24p.

Ben Yehoshua, S. 1978. Delaying deterioration of individual citrus fruit by seal-packing in film of high-density polyethylene. 1. General effects. Proceedings of the International Society of Citriculture. pp. 110-115.

Beuchat, L.R. and Ryu, J.H. 1997. Produce handling and processing practices. Emerging Infectious Diseases 3 (4)


Boyette, M. D., Sanders, D. C. and Estes, E. A. Estes. 1992. Postharvest Cooling and Handling of Cabbage and Leafy Greens. North Carolina Agricultural Extension Service Publication Ag-413-5.

Buyckx, M. The international community's commitment to combating micronutrient deficiencies nutrition Planning Assessment and Evaluation Service, FAO.

Cantwell, M. and Suslow, T. 2006. Cabbages (Round and Chinese types): Recommendations for maintaining postharvest quality. UC Davis Postharvest Technology Research Information Center.

Fernando, M.D. 2006. Country paper: Sri Lanka (2). In: APO. 2006. Postharvest Management of Fruit and Vegetables in the Asia-Pacific Region. Asian Productivity Organization (APO) and FAO. pp. 264-275.

Ferrante, A. and Maggiore, T. 2007. Chlorophyll a fluorescence measurements to evaluate storage time and temperature of Valeriana leafy vegetables. Postharvest Biology and Technology 45:73-80.

Fonseca, J. (ed.). 2004. Western Vegetable Newsletter Vol. 2 (5) www.cals.arizona.edu/crops

Gast, K.L.B. 1991. Containers and Packaging Fruits & Vegetables, Kansas State University, March 1991. http://www.oznet.ksu.edu

Herrera, M.G., Nestel, P., El Amin, A., Fawzi, W., Mohamed, K. & Weld, L. 1992, Vitamin A supplementation and child survival. Lancet, 340:267-271.

Huang, C.C. 2006. Country paper: Republic of China. Postharvest Management of Fruit and Vegetables in the Asia-Pacific Region. Asian Productivity Organization (APO) and FAO. pp. 117-122.

Jiang, T. and Pearce, D. 2005. Shelf-life extension of leafy vegetables: evaluating the impacts. Impact Assessment Series Report No. 32. 62pp.

Jobling, J. undated. Postharvest Ethylene: A critical factor in quality management. Sydney Postharvest Lab Information Sheet www.postharvest.com.au [email protected]

Jordan, J. L.; Shewfelt, R. L.; Thai, C. N. and Prussia, S. E. 1987. Transporting perishable commodities: The economic impact of separating ethylene-generating from ethylene-sensitive produce. Department of Agricultural Economics Report, Georgia Experiment Station, Experiment, GA, P. 18.

Kader, A. A., ed. 2002. Postharvest Technology of Horticultural Crops. Oakland: University of California, Division of Agriculture and Natural Resources Publication, 3311, P. 535.

Kader, A.A. 2006. The Return on Investment in Postharvest Technology for Assuring Quality and Safety of Horticultural Crops.

Kader, A. A. and Rolle, R. S. 2004. The Role of Postharvest Management in Assuring the Quality and Safety of Horticultural Produce. Rome, FAO Agric. Serv. Bull., 152, P. 51.

Kitinoja, L. and Kader, A. A. 2002. Small-scale Postharvest Handling Practices: A Manual for Horticultural Crops. Fourth edition. Davis, University of California, Postharvest Horticulture Series 8E, P. 260.

Kleiber, A., Porter, K. and Collins, G. 2001. Chinese cabbage management before and after harvest. In: O’Hare, T., Bagshaw, J., Wu Li and Johnson, G.I., ed., Postharvest handling of fresh vegetables. Proceedings of a workshop held in


Beijing, People’s Republic of China, 9-11 May 2001, ACIAR Proceedings 105:92-99.

O’Hare, T.J., Able, A.J., Wong, L.S., Prasad, A. and McLauchlan, R. 2001. Fresh-cut Asian vegetables-pak choi as a model leafy vegetable. In: O’Hare, T., Bagshaw, J., Wu Li and Johnson, G.I., ed., Postharvest handling of fresh vegetables. Proceedings of a workshop in Beijing, P.R.C., 9-11 May 2001. ACIAR Proceedings105:113-115.

Rapusas, R.S. 2006. Country paper: Philippines (2). In: APO. 2006. Postharvest Management of Fruit and Vegetables in the Asia-Pacific Region. Asian Productivity Organization (APO) and FAO. pp. 227-244.

Sanders, D.C. undated. Cabbage Production. North Carolina State University Horticulture Information Leaflet HIL-07.

Somjate, S. 2006. Packaging and transportation of fruits and vegetables for better marketing. In: APO, 2006. Postharvest Management of Fruit and Vegetables in the Asia-Pacific Region. Asian Productivity Organization (APO) and FAO. pp. 15-22.

Stephens, J.M. 2003. Cabbage, Chinese — Brassica campestris L. (Pekinensis group), Brassica campestris L. (Chinensis group). Horticultural Sciences Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. HS569.

Sullivan, G.H., L.R. Davenport, and J.W. Julian. 1996. Precooling: Key factor for assuring quality in new fresh market vegetable crops. p. 521-524. In: J. Janick (ed.), Progress in new crops. ASHS Press, Arlington, VA.

Suslow, T. 1997. Postharvest chlorination: Basic properties and key points for effective disinfection. Division of Agriculture and Natural Resources, University of California, Davis, Publication 8003. http://danrcs.usdavis.edu.

Thompson, J. F., Reid, M. S., Postma, J., Mitchell, F. G. and Yang, S. F. 1989. Evaluation of ethylene control systems. Annual Report of the California Iceberg Lettuce Research Program, Salinas, CA, P. 6.

Vanndy, M. and Buntong, B. 2007. Cambodia status of vegetable value chains. Paper presented in the RETA 6376 Inception Workshop, 3-5 July 2007, Vientiane, Laos.

Weinberger, K., Genova, C. and Acedo, A. 2007. Perishability of horticultural crops along the supply chain: some evidence from Southeast Asia. Paper presented in the International Symposium on Improving the Performance of Supply Chains in the Transitional Economies, 23-27 September 2007, Hanoi, Vietnam.

Wills, R.B.H., Warton, M.A. and Ku, V.V. (2000). Ethylene levels associated with fruit and vegetables during marketing. Australian Journal of Experimental Agriculture 40:357-492.

Wilson, L.G., M.D. Boyette, and E.A. Estes. 1995. Postharvest Handling and Cooling of Fresh Fruits, Vegetables and Flowers for Small Farms. Leaflet 800-804. North Carolina Cooperative Extension Service. 17p. http://www.foodsafety.org/nc/nc1055.htm


Workshop Summary

Summary of fresh produce handling technologies for leafy vegetables considered to be adapted and developed by Cambodia, Laos, and Vietnam teams: Purpose Cambodia Lao PDR Vietnam Prolong shelf life

Evaporative cooling storage (ECS); integrate other treatments Ice bottle for cooling

ECS, adapting other simple structure (e.g. Sri Lanka design), especially for cabbage storage; integrate other treatments

Use of ethylene scrubbers in MAP to control yellowing in Chinese mustard and kangkong

Packaging Improve existing MAP system for all priority vegetables

Improve existing MAP system for all priority vegetables

Ice packaging

Bacterial soft rot control in cabbage

Use of calcium carbonate (lime), alum and botanical extract

to be developed as part of storage management

Use of calcium carbonate (lime), alum and botanical extract

Addressing problems due to oversupply

Other recommendations: proper cropping plan, supply chain approach to solving the problems; market understanding; product diversification

Processing Improved quality and shelf life of fermented leafy vegetable

Optimize fermentation process for cabbage by considering techniques from China, Myanmar, Thailand, and Vietnam and on salting

Optimize fermentation process for Chinese mustard by considering techniques from China, Myanmar, Thailand, and Vietnam and on salting

Optimize RIFAV fermentation technique for Chinese mustard and cabbage

Develop dehydrated leafy vegetable

Drying cabbage by solar dryer and vacuum fryer

Use of solar dryer (optional activity)

Other recommendations: Modifying the salt concentration and pH (using food-grade citric acid) is the key to improving shelf life of fermented products.


PART III: Processing technologies for leafy vegetables

Processing Technologies for Leafy Vegetables in Yunnan, China

Li Hong

Deputy Director and Associate Professor Administration Department of Science and Technology Industry

Yunnan Academy of Agricultural Sciences (YAAS) Deputy General Manager

Yunnan Agricultural Science and Technology Industry Management Co., Ltd. Kunming, Yunnan, China

Introduction

China is the world’s leading producer, consumer, and exporter of processed vegetables. Processed vegetables include dehydrated, pickled/fermented, frozen and canned products, juice, ketchup, powder, and pigment extract, such as the pigment extract from the purple variety of common cabbage, which is mainly used by the food industry in a manner similar to vegetable powder (e.g. garlic and ginger powder). Dehydrated vegetables account for about 60% of the world’s total export. China produces about 300,000 tonnes of dehydrated vegetables yearly. Its annual exports of pickled or fermented vegetables are about 200,000 tonnes (as salted products) to Japan and more than one million tonnes to South Korea and Southeast Asia. China itself is a big consumer of pickled products. Canned vegetables are normally exported to Western countries or supplied to the military (e.g. freshwater bamboo root, mushroom, spinach). Vegetable juice or ketchup (e.g. carrot, tomato, cucumber) are usually mixed with fruit or made into drinks. Frozen vegetables are a more recent development. In Yunnan Province, the main processed vegetables are dehydrated, pickled, frozen and canned products. Dehydrated vegetables are classified as AD (dehydrated by hot air) or FD (dehydrated by vacuum freezing) products. The quantity of AD vegetable is much more than the FD products, with a share of greater than 85%. Aside from leafy vegetables (e.g. common cabbage, spinach, celery), other vegetables that are processed into dehydrated products include root/stem vegetables (e.g. radish, carrot, garlic, onion), floral vegetables (e.g. broccoli, cauliflower) and wild mushroom. For pickled products, the main export vegetables are artichoke and wild mushroom. Other pickled vegetables such as leafy/stem mustard, Chinese onion and common cabbage are produced mainly for local consumption. Production of frozen vegetables started two years ago and the technology was used mostly for wild


mushroom processing. It was quickly adopted for other vegetables and at present, freezing technology is a normal processing technique that covers all types of vegetables. Canned vegetables, mainly mushroom, bamboo root, peas and sweet corn, occupy only a very small share in the processing industry. This paper describes dehydrated vegetable processing and pickled vegetable processing of leafy vegetables in Yunnan, China.

Dehydrated Vegetable Processing Processing flow Figure 1 shows the processing flow to produce dehydrated leafy vegetable. Raw material selection and grading This is done to eliminate vegetables not suitable for processing. Selection and grading are based on dimension, weight, appearance, and maturity stage. Over-mature, insect-damaged, diseased, mechanically damaged, malformed, and off-types are discarded. Dimension grading is based on size, length, and thickness. Maturity of produce is mainly determined based on appearance.

Materials selection & grading

Washing & disinfection

(Peeling)

Cutting

Blanching

Drying

Sorting

Packaging

Figure 1. Processing flow for producing dehydrated leafy vegetable.


Washing and disinfection Washing is done to remove dust, soil, surface microorganisms, and pesticide residues. Leafy vegetables are washed by spray water or in a pond of water added with 600 ppm chlorine, 0.5%-1.0% hydrochloric acid or 0.05%-0.1% potassium permanganate (Fig. 2). The internal stem and leaves of common cabbage are eliminated during washing. Sometimes a washing machine is used to clean some vegetables. Cutting The vegetable is cut before further processing. Different cutting machines are used depending on the desired shape and size of the product (Fig. 2). Tough stems of some leafy greens are trimmed off. Blanching Blanching is a short heat treatment done by steaming or hot water dipping (Fig. 2). During hot water blanching, the temperature is set at 85-95°C instead of 100°C. The vegetable is conveyed to a steam-generating machine or immersed in hot water for about 2 to 3 minutes or longer, depending on the type of produce. From the heat treatment chamber, the vegetable flows out into ice water for immediate cooling. Excess water is removed by hand with the aid of a mesh screen or centrifuge (Fig. 2). Drying After cooling, the vegetable is placed on a stainless steel screen, plate, or tray with small holes, and put in the drying chamber supplied with hot steam. The steam rises from bottom to dry the product. The temperature is set at about 85 °C and then lowered gradually to 50°C. Drying may take 5-6 hours. For uniform drying, the vegetable is turned using a spade or fork. In other processing companies, leafy vegetables such as common cabbage are treated with 10% dextrose solution for 30 min before drying. In northern China, the vegetable is often dried using a local oven made of bricks and mud called kang and heated by coal. Table 1 shows the desired fresh and dry weight ratio after drying of some leafy vegetables and other types of vegetables. Sorting and packaging The dried vegetable is sorted on a sorting table to cull out partially dried, off-sized, agglomerated products as well as foreign materials such as hair and other undesirable debris, usually with the use of detecting equipment such as a magnifying glass, vibration filter, metal detector, or X-ray machine (Fig. 3).


The selected product is placed in a big plastic bag for about 1-3 days to allow dried product to absorb moisture. Finally, the dried product is repacked in plastic bag at specific weights, placed in cartons, and stored at 0-5°C and below 65% RH.

Figure 2. Washing, cutting, blanching and removal of excess water in leafy vegetable for processing to dehydrated product.


Table 1. Desired fresh and dry weight ratio after drying for some vegetables.

Vegetable Fresh/dry rate Vegetable Fresh/dry rate

Common cabbage

14-20:1 Carrot 10-16:1

Spinach 16-20:1 Tomato 18-20:1

Onion 12-16:1 Pea 7-14:1

Potato 5-7:1 Pumpkin 14-16：1

Hot pepper 3-6:1

Figure 3. Sorting, packing and storage of dehydrated leafy vegetable.

Pickled Vegetable Processing Pickled vegetables are very popular in Yunnan. Leafy vegetables that are often pickled include mustards (leaf and stem), Chinese kale and common cabbage. Other vegetables processed into pickles include cucumber, pepper, radish and Chinese onion.


Processing flow Figure 4 illustrates the processing flow for producing pickled leafy vegetable.

Raw material selection Leafy vegetable for pickling is selected in the same manner as that for dehydrated vegetable processing. Inedible parts such as tough stems and roots are removed. Sun-drying Selected vegetable is exposed to the sun for 1-2 days to reduce water content and make them soften or flaccid to avoid breaking or tearing of leaves and stems during subsequent operations. Washing The vegetable is washed in fresh water to remove dust and other extraneous materials. Excess water on the leaf surface is then removed by shaking manually. Twisting and kneading The vegetable is placed into a suitable container, then salt (about 15% of the total volume of produce being pickled), hot pepper powder, ginger, and monosodium glutamate are added. The vegetable is mixed, twisted, and kneaded to allow maximum absorption of the condiments. Fermentation The prepared vegetable is put into a pond or pot disinfected with alcohol, covered and pressed with weights for fermentation. The fermentation period varies from 3-4 days in summer and 6-7 days in winter. The vegetable has to be turned periodically to allow uniform fermentation and dissipate the heat and bad smell. Turning the vegetable is done 3-4 times during the fermentation period. Packing and storage The pickled vegetable is transferred from the fermentation pond to pots or plastic barrels and covered with the salty liquid. The pot must be airproof and placed in a shaded area or cold room.


Raw material selection

Sun-drying

Washing

Removal excess water

Turn the vegetable

Heavy press

Put in fermentation pot

Twisting and kneading

Heavy press

Finished product

Figure 4. Processing flow for producing pickled leafy vegetable.

References Li Yanyun. 2004. Hot air and frozen dehydrated vegetable processing techniques.

Jindun Press. Zheng Yonghua, Gu Zhenxin, Hanyongbin. 2002. Vegetable processing practical

techniques, Jindun Press. Liu Guofen. 2001. Questions and answers to vegetable processing techniques, Jindun

Press Schafer, W. and S.T. Munson. 1990. Freezing fruits and vegetables. Extension

Service, University of Minnesota, USA. (www.extension.umn.edu/distribution/nutrition/DJ0555.html)

Wu Juhong. 2007. Cut fresh vegetable processing and circulating, China Agricultural Scientific and Technological Press.


Processing Technologies for Leafy Vegetables in Myanmar

Win Win Kyi

Small-scale Enterprise Advisor, AVRDC-ADB RETA 6208 AVRDC-ADB Post harvest Project Office, P.O. Box 3938, Vientiane, Lao PDR

Introduction

Food processing is the most important source of income and employment in Myanmar. The Food and Agriculture Organization of the United Nations has stated that value addition through marketing and processing raw products can be much greater than the value of primary production. In Myanmar, more than 80% of the workforce is employed in the agricultural sector and it is the primary source of income. Processing is particularly important, as other agricultural sectors are unable to absorb the country’s growing labor force. There is therefore a need for rural income diversification by the creation of small-scale food processing enterprise as a key strategy for rural development This paper describes appropriate processing technologies in the rural area in Myanmar and focuses on simple and inexpensive techniques for leafy vegetables. When vegetables are maturing in the field they are changing from day to day. Harvesting and processing of several vegetables are rigidly scheduled to capture this peak quality. When harvested, vegetables undergo rapid deterioration, especially in the humid tropics where the prevailing environmental conditions accelerate the process of decomposition. After the vegetables are harvested, they may quickly pass beyond the peak quality condition due to the following processes:

1. Loss of sugars due to their consumption during respiration or conversion to starch; loss is slower under refrigeration, but there is still a great change in freshness and flavor within 2-3 days.

2. Production of heat when stockpiles of vegetables are transported or held prior to processing.

Cooling only slows down the rate of deterioration, it does not prevent it. Vegetables differ in their resistant to cold storage; each type of vegetable has its optimum cold storage conditions.


There are several options for processing vegetables including drying, freezing, fermentation, and canning. However many of these are inappropriate for small-scale use in Myanmar. For instance, canning vegetables on a small scale has serious food safety implications and contamination with human pathogens is a possibility. Freezing vegetables also is not economically viable on a small scale. Drying and fermentation are cheap and energy-efficient means of preserving perishable raw materials because they do not require sophisticated equipment. Drying and fermentation process have been employed for generations to preserve food for consumption at a later date and to improve food security.

Background Myanmar shares borders on the north and northeast by the People of Republic of China, on the east and the southeast by the Lao People’s Democratic Republic and the Kingdom of Thailand, on the south by the Andaman Sea and the Bay of the Bengal, and on the west by Bangladesh and the People’s Republic of China. The country has three seasons: rainy, hot, and cold. Generally, Myanmar enjoys a tropical monsoon climate. However, the climatic conditions differ widely from place to place due to widely differing topographical situations. For instance, Central Myanmar has an annual rainfall of less than 40 inches while the Rakhine coast gets about 200 inches. The average highest temperature in Central Myanmar during summer months (March-April) is nearly 48°C while in the Chin State about 20°C. Temperatures of towns vary according to their location and elevation. Myanmar is made up of 135 national races of which the main ethnic groups are Kachin, Kayah, Kayin Chin, Burma, Mon, Rakhine, and Shan. The population is estimated at 55 million with almost equal male and female population. The population density per square mile has been increasing from 46 to 188 over the past century (1900-2000). Myanmar has cultivated land of 18.2 million hectares. At present, the nation put under crop cultivation about 24 million acres annually. If the vacant, fallow, and wetlands are reclaimed, there will be another 20 million acres of cultivated land. Thus it can be said that the nation is rich in agriculture land. Rice is the leading crop and the staple food. There are other various crops being cultivated, including beans and pulses, corn, sesame, cotton, sugarcane, fruit and vegetables.


The industrial sector has in the past been dominated by state economic enterprises, with private businesses mostly confined to small-scale activities in industrial processing. As a consequence, value-added manufacturing has low share in GDP. However, in late 1988, the government officially pronounced a more market-oriented, open economic policy in place of the central approach, which has been followed for nearly three decades. It is equally important to note that Myanmar’s economic development has been constrained by the country’s isolation from the world economy under a rigid central planning system.

Leafy Vegetable Processing Technologies Preliminary operations Vegetables are subjected to several preliminary operations after harvesting and before processing. These include cleaning or washing and inspection, selection, and grading based on firmness, cleanness, size, weight, color, shape, maturity, and freedom from defects. Drying and dehydration process

Principles. Drying involves removal of a large part of the water contained in a product to reduce the reactions that lead to deterioration. The water is eliminated by evaporation into the surrounding air. The energy source for evaporation may come from the sun, warm air, or combustion heat. Proper drying requires knowledge of three fundamental parameters:

1. The capacity of the surrounding air to absorb the water vapor given off by the product. The capacity depends on the percentage of moisture already present in the air before it enters the dryer and on the air temperature.

2. The velocity of the air going over the product’s surface must be high (up to a certain limit) especially at the beginning of the drying process, to take the moisture away rapidly.

3. Drying has to occur rapidly to avoid the product from going moldy but not so rapidly that a crust could form on the product surface. The temperature must not be too high because the product may blacken and spoil.


To dry the product properly, the characteristics of the fresh product have to be taken into account (fatty fish is not dried in the same way as leafy vegetables), as well as those expected of the final product (texture, color, specific taste). The quality of the fresh and dried produce before and after drying must be determined. Types of dryers. There are several types of dryer for food processing, such as fuel-fired dryers, electric dryers, and solar dryers. The sun is a cheap source of energy, but it is important to check first the availability of solar energy at the site before deciding to use a solar dryer. Table 1 shows a solar analysis grid. Preparing the product before drying. Washing removes dirt, surface microorganisms, and other debris. The water must be clean and treated with disinfectant. The produce is then sorted to choose the best raw material for drying without undesirable changes. It may then be cut into cubes, slices, strips or filets to make the drying process faster and easier. This operation is necessary when the product is thick, or else the drying will be too slow and microorganisms may be able to infect the produce. Pretreatments. Blanching, sulfuring, and other pre-drying treatments could improve the storage potential and taste of the dried product. The drying process. Drying increases the preservation period of a product but it changes the product quality in terms of taste, texture, and nutritional value. Appreciating the product’s quality depends on the consumer’s eating habits. A high temperature over a certain period of time sets off two reactions: on enzymatic browning and hardening, which degrades quality and may hinder the drying process. Other forms of deterioration include loss of aroma, destruction of vitamins, and denaturation of proteins. Packaging and storing of the dried product. The dried product must be packaged soon after drying to avoid contaminants, dust, and other debris when the product has cooled down. Aside from promoting sale and providing information (quantity, production date) about the product, the packaging system protects the product against filth (germ, insect, dust), moisture, light, oxygen, and physical deterioration and makes handling easier during transport and marketing. The packaging material to use depends on the nature of the product, storing and handling conditions (temperature, humidity, risk of deterioration), protective capacity of the materials, practicality, availability, and cost.


Plastic containers and bags are common packaging materials. Plastic containers used to handle fresh and processed vegetables are tough, easy to handle due to their light weight, can be reused, and facilitate stacking without damaging the product. Initially, the cost of plastic containers and bags is high, but if protected from sun and extreme conditions, they can last for years. In developed countries, various plastics are used at all stages in postharvest handling and processing of fruit and vegetables. Polyvinylchloride (PVC) is used primarily for wrapping, while polypropylene (PP) and polyethylene (PE) bags are most widely used for packaging minimally processed products. Plastic bags are suitable for handling small amounts of vegetable products and are commonly used in supermarkets and retail stores in developed and developing countries. Vacuum packaging extends the shelf life of vegetables for long periods. This technique relies on withdrawing air from the package with suction. Removal of air retards the development of enzymatic reactions and bacterial spoilage. Vacuum packaging and gas flushing establish a modified atmosphere quickly and increase the shelf life and quality of processed products. In addition to vacuum packaging, the specifics of handing must be taken into account, especially time delays and temperature fluctuations. Advice on consuming dried product. The product is fully soaked in water to allow absorption of water lost during drying. Half an hour to two hours give acceptable results. Two to six hours give a more tender product. Water must be added constantly for the product not to be exposed to air. During soaking, vegetables lose of a lot their flavor. They can be spiced up with garlic, onion and various herbs. The product must be cooked using the soaking water because it contains the minerals from the produce. Dried cabbage and green vegetables can be cooked after soaking until a tender texture develops. Producing dried cabbage. Figure 1 shows the flow diagram for drying cabbage leaves. After discarding the spoiled leaves and the core, the cabbage is washed with clean water and cut into thin slices (about 4 mm thick) for fast drying. The slices can be blanched before drying, such as by dipping in boiling water for 3 minutes or steaming for 5 seconds. Blanching too long may cook the cabbage. Sodium bicarbonate can be added to the boiling water (10 gm per liter). Blanching speeds up the drying process. However, it not recommended for slow drying because of the risk of the blanched cabbage fermenting. The maximum drying temperature is 55°C. It is recommended that the final moisture content should be 4%. End of drying may be determined when the leaves become hard and brittle. The drying ratio is 1:18. In indirect drying, the color stays very close to that of the fresh product.


Advice for consumption is that dried cabbage must be soaked for 30 minutes in hot water before using. Dried green tea leaves. Figure 2 shows the flow diagram for producing dried green tea leaves. The first stage in producing dried green tea leaves is to inactivate the enzyme whose action is fundamental to the preparation of black tea. After plucking the tea leaves, they are roasted in a shallow pan over a fire or using steam. The duration varies from 15 seconds to 7-8 minutes. This step is followed by a series of operations: pressing, rolling, and kneading the leaf to produce a mass with uniform moisture content. Traditionally this process is done by hand or by simple apparatus. A half-hour resting step allows the mass to mature before drying on a screen above a stove or by exposure to the sun. Final desiccation is carried out in rotary cylinder using hot air.

Washing

Discarding the spoiled leaves

Cutting

Blanching

Drying

Packaging

Figure 1. Flow diagram for producing dried cabbage.


Plucking

Roasting or Steaming

Pressing

First Rolling

Kneading

Resting

Drying

Second Rolling

Drying

Packing

Figure 2. Flow diagram for producing dried green tea leaves.

Fermentation technologies Diversity of fermented foods. Numerous fermented foods are consumed around the world. Each nation has its own types of fermented food, representing the staple diet and the raw ingredients available in that particular place. Although the products are well known, they may not be associated with fermentation. The methods of producing many of the world’s fermented foods came about by chance. Several fermentable products arise from lactic acid fermentation, which enhances the nutritional value of a food product through increased vitamin levels and improved digestibility. These products are extremely important in meeting the nutritional requirements of a large proportion of the world’s population. Desirable fermentation. It is essential with any fermentation process to ensure that only the desired bacteria, yeast, or mold start to multiply and grow on the the produce. These organisms could suppress other microorganisms, which may be pathogenic, cause food poisoning, or spoil the fermentation process. Most food spoilage organisms cannot survive in either alcoholic or acidic environments. Therefore, the production of both these end products can prevent a food from spoiling and extend the shelf life. Alcoholic and acidic


fermentations generally offer cost-effective methods of preserving food for people in Myanmar, where more sophisticated means of preservation are unaffordable. Lactic acid fermentation is carried out under three basic types of conditions: dry salted, brined, and non-salted. Salting provides a suitable environment for lactic acid bacteria to grow, which imparts an acid flavor to the vegetable. For pickling, any variety of common salt is suitable as long as it is pure; impurities or additives can cause problems. Salt with chemicals to reduce caking should not be used as they make the brine cloddy. Salt with lime impurities can reduce the acidity and shelf life of the final product. Salt with iron impurities can result in the blackening of the vegetables. Magnesium impurities impact a bitter taste. Carbonates can result in pickles with a soft texture. Dry salted fermented vegetables. With dry salted fermentation, the vegetable is treated with dry salt (Fig. 3). The salt extracts the juice from the vegetable and creates the brine. The vegetable is prepared, washed in potable cold water, and drained. For every 100 kg of vegetables, three kg of salt is needed. The vegetables are placed in a layer of about 2.5 cm depth in the fermenting container. Salt is sprinkled over the vegetables. Another layer of vegetables is added and more salt is added. This is repeated until the container is three- quarters full. Cloth is placed above the vegetable and a weight is added to compress the vegetable and assist the formation of brine, which takes about 24 hours. As soon as the brine is formed, fermentation starts and bubbles of carbon dioxide begin to appear. Fermentation takes between 1-4 weeks, depending on the ambient temperature. Fermentation is complete when no more bubbles appear, after which the pickle can be mixed with vinegar, spices, oil, and spices. Brine salted fermented vegetables. Brine is used for leafy vegetables, which inherently contain less moisture. A brine solution is prepared by dissolving salt in water (15-20% salt solution). Fermentation takes place in a brine of about 20° salometer. As a general guide, a fresh egg floats in a 10% brine solution. Properly brined vegetables will keep well in vinegar for a long time. The duration of brining is important to the overall keeping qualities. The vegetable is immersed in the brine and allowed to ferment. The strong brine solution draws sugar and water out of the vegetable, which decreases the salt concentration. It is crucial that the salt concentration does not fall below 12%, otherwise the condition does not allow for fermentation. To achieve this, extra salt is added periodically to the brine mixture.


Once the vegetable has been brined and the container sealed, microorganisms will rapidly develop in the brine. The natural controls that affect the microbial population during fermentation include the concentration of salt and temperature of the brine and the availability of fermentable materials and the numbers and types of microorganisms present at the start of fermentation. The duration of fermentation is correlated with the concentration of salt in the brine and its temperature. Most vegetables can be fermented at 12.5-20°C. At higher salt levels of up to about 40° salometer, the sequence is skewed towards the development of a homo fermentation, dominated by Lactobacillus plantarum. At the highest concentration of salt (about 60° salometer) the lactic fermentation ceases to function and if any acid is detected during brine storage, it is acetic acid, presumably produced by acid-forming yeasts, which are still active at this concentration of salt. Non salted, lactic acid fermented vegetables. Some vegetables are fermented by lactic acid bacteria, without the prior addition of salt or brine. Example of non-salted products includes gundruk (consumed in Nepal), sinki, and other wilted fermented leaves. The fermentation process relies on the rapid colonization of the food by lactic-acid producing bacteria, which lower the pH and make the environment unsuitable for the growth of spoilage organisms. Oxygen is also excluded. Restriction of oxygen ensures that yeasts do not grow.


Fresh cabbage

Cleaning

Washing

Size grading

Cutting and shredding

Adding 2.5% salt

Fermentation process (2-4 weeks)

Lactic acid production (1-2%)

Packaging in glass jars

Figure 3. Flow diagram for producing fermented cabbage.

Summary In Myanmar, many farmers are often forced to give produce away or let it rot due to the inability to store large quantities of fresh produce without incurring heavy losses; small local markets for the large quantities of fresh produce in season; and inefficient distribution and transportation to meet the demand in urban areas. To minimize the problem, many organizations from the government and nongovernmental sectors in Myanmar have made efforts to address seasonal gluts through value-addition activities such as processing. Vegetables are low-acid foods subject to a wide range of microorganisms that may lead to spoilage and the possibility of food poisoning. Vegetables can be processed by heating to destroy the bacteria, or by pickling, salting, or drying to inhibit bacterial growth. Processing should be employed to solve the problem of oversupply and low price of fresh produce during production peaks, and to serve market demand.

References Barbosa-Canovas, G.V. Fernandez-Molina, J.J., Alzamora, S.M., Tapia, M.S., Lopez-

Malo, J. and Chanes, J.W. 2003. Handling and Preservation of Fruits and


Vegetables by Combined Methods for Rural Areas. FAO Agricultural Services Bulletin 134

Rozis, J.F. 1997. Drying Foodstuffs. Bachhuys Publishers, Leiden Lal, G., Siddappa, G. S. and Tandon, G. L. 1986. Preservation of Fruits and

Vegetables. Indian Council of Agricultural Research, India Battcock, M. and Azam-Ali, S. 1998. Fermented Fruits and Vegetables. FAO

Agricultural Services Bulletin 134 Fellows, P. and Hampton, A. 1992. Small-scale food processing: A guide to

appropriate equipment. Intermediate Technology Publication Proceeding of Regional Workshop on “Agribusiness Development through Agricultural

Engineering Application to Agricultural Products. 2001. Value-added Food Products Processing for Micro-Income Generation of Rural

Communities in Myanmar. 2002.


Table 1. Analysis grid of the availability of solar energy on the drying site 1. Do you know what the average daily radiation on a horizontal surface (ES) is, in the area where the dryer is to be set up, and for the harvesting period (in kWh per day and per square meter)?

< 2 (0) 2 to 4 (3) 4 to 6 (6) > 6 (9)

If you were able to answer this question, go straight to question 5. If not, we will try to estimate it by answering the following question. 2. What is the average number of hours of sunshine per day? < 4 (0) 4 to 7 (1) 7 to 10 (2) > 10 (3) 3. What is the total length of a solar day (from sunrise to sunset) in hours? < 8 (0) 8 to 10 (1) 10 to 12 (2) > 12 (3) 4. What kind of clouds are there? Thick (0) Thin or misty (2) No clouds (3) Thick cloud is when the sky is entirely overcast: there is only diffuse solar radiation T1= the sum of answers 2+3+4 T1= The value of solar radiation is given by the following: T1 < 3 ES < 2 k W h 3< T1 < 6 2 < ES < 4 k W h 6< T1 < 8 4 < ES < 8 k W h T1>8 ES > 6 k W h The estimated value of ES can then be put in the appropriate category in question 1. 5. What is the average number of consecutive days in which the sun shines less than four hours? 0 (0) 3 (3) 1 (1) > 4 (4) 2 (2)

6. At what latitude is the dryer site (in degrees south or north)? > 45 (0) 30 to 15 (2) 45 to 30 (1) < 15 (3) 7. At what altitude is it (in meters)? < 500 (0) 500 to 1,000 (1) 1,000 to 2,000 (2) 2,000 to 3,000 (3) > 3,000 (4) 8. How can one describe the climate? Equatorial or humid tropical (0) Maritime or temperate (1) Continental (2) Desert or semi-arid (3) An equatorial climate is hot and damp with very little variation in temperature. A maritime climate is milder. In a desert climate, there are great variations in temperature but very little humidity. A continental climate is close to that, but less extreme. 9. What is the average relative air humidity during the drying period (in %)? > 85 very humid (0) 85 to 65 quite humid (1) 65 to 45 quite dry (2) < 45 very dry (3) Relative air humidity above 85% is difficult for humans to bear. When the temperature is high, objects stick to the skin, one feels like one is in a stream bath, it is very difficult to get dry. Air with less than 45% humidity dries everything out. 10. Are there any particles in the air (pollution from smoke, car exhausts, dust, and sand)? High concentration (0) Low concentration (1) None at all (2)

The total T2 = the total of answers 6+7+8+9+10 T3 = T1+T2-5 =

If T3 < 6 the physical conditions are not right for solar drying, one must resort to another form of energy. If 6 < T3 < 20, another source of energy must be provided at a relay. If T3 > 20, conditions favor using solar energy.


Processing Technologies for Leafy Vegetables in Thailand

Varit Srilaong, Ph.D.

Division of Postharvest Technology King Mongkut’s University of Technology Thonburi

Bangkok, Thailand

Introduction Vegetables are high-value crops grown in home gardens for family consumption and/or income generation or in large areas of land as commercial ventures but usually dominated by small-scale producers. Vegetables are also important in human nutrition, being rich in essential minerals, vitamins, dietary fibers, fats, starch, and energy. Vegetables are major sources of vitamin C. Vitamin C, together with carotenoids, anthocyanins, and glucosinolates, are known antioxidants that can prevent several human diseases. Dietary fibers in vegetables, which include cellulose, hemicellulose, pectin, and lignin, also contribute to improved human health. Vegetables are an essential part of the human diet and add flavor, aroma, and color to many food preparations. The consumption of vegetables varies among countries and regions. The average world consumption of vegetables is around 85 kilograms per person per year. In industrialized countries, the consumption is around 120 kg per capita. It is around 30 kg per capita in Africa and around 150 kg per capita in China. In Thailand, commercially important leafy vegetables include cabbage, Chinese cabbage, spinach, lettuce, celery, and mustard. Leafy vegetables are highly perishable. Thus, processing is one of the important techniques to reduce the postharvest loss problem. Postharvest loss of fresh vegetables is estimated at 20-50% in tropical countries. Aside from solving the perishability problem, processing can improve the eating quality of some bitter-tasting leafy vegetables. This paper presents the processing technologies developed and/or commercially used for leafy vegetables in Thailand, focusing on some simple techniques.


Fermentation Technologies Fermentation is a traditional means of preservation. Salt has long been used to preserve foods. Brine fermentation involves complex microbial, chemical, and physical reactions and gives the final product unique flavor characteristics. Almost all vegetables produce substances as nutrients for the growth of fermentation-related microorganisms. In general, fermentation is desired for most vegetables that are given a brine treatment. Fermenting vegetables serves two main functions: (1) encourage growth of certain microorganisms that are responsible for desired sensory changes; and (2) develop a preservative effect.

Leaf mustard pickle Leaf mustard (Brassica juncea) is grown wildly in Thailand, especially in the north, where the temperature is lower than in the other areas. Most leaf mustards are used for pickle production. The pickled product is yellowish, crispy, and sour or salty in taste. Microbiology of leaf mustard fermentation. The microorganisms responsible for the fermentation of leaf mustard are the lactic acid bacteria, Leuconostoc mesenteroides, Lactobacillus spp., and Pediococcus spp. Usually when leafy vegetables are packed in salt or in brine solution, soluble nutrients from the commodity support the growth of lactic acid bacteria. General processing of leaf mustard: a case study of SME in Thailand. The mature green leaf mustard (60-70 days after cultivation) is cut and transported to the production plant or left in the field for one day to dry (especially during the rainy season). The leaf mustards are then trimmed and layered in a fermentation well or tank, and covered with brine solution. The vegetable is covered with a heavy plastic sheet and weights are placed on top. In general, the longer the fermentation interval, the higher the salt concentration used. The concentration of brine solution is about 20% and the duration of fermentation depends on the desired characteristic of final product (Fig. 1).


Cut mature leaf mustard and transport to processing plant

Trim and place in fermentation tank

Add 20% of brine solution or dry salt

Cover with plastic sheet with weights

1 night

Transfer to sauce, 4-5 days*

Pack in plastic bag or vacuum pack

Market

3 months - 1 year

Wash 3 times with tap water

Adjust pH for 1 night

Wash again with tap water and drain

Filling in plastic bag with sauce

Vacuum pack

Pack in transportation box

Market

Figure 1. General flow chart of leaf mustard pickle processing. *The composition of sauce depends on the processor. In general, it contains monosodium glutamate (MSG), acidifying agent (citric acid), firming agent (calcium chloride), sugar, herb, spice (chili), vinegar, and soy sauce or fish sauce.

Quality standards of leaf mustard pickle. The following are the specifications of the quality standards of leaf mustard pickle as specified by Thailand’s standards agency:

Definition: Leaf mustard pickle is a product from green leaf mustard (Brassica juncea) Ingredients of pickle sauce: Water, soy sauce or fish sauce, vinegar, salt, sugar and additives such as

chili, herbs, etc. pH of finished product: < 4.5 Additives:

1. MSG < 0.25% 2. Acidifying agent: acetic acid, citric acid, malic acid, tartaric acid, lactic

acid, ascorbic acid 3. No artificial coloring 4. No preservative


5. Firming agent: NaCl < 1,000 mg/kg or CaCl2 < 350 mg/kg 6. Contamination: tin < 250 mg/kg

Microorganism: 1. Total plate count < 1×103 colonies/ g of sample 2. Coliform < 3/ g sample 3. Yeast and fungi < 100 colonies/ g of sample

Packaging of leaf mustard pickle. Pickled mustards may be displayed bare in the market (Fig. 2-3) or packed in different kinds of containers (Fig. 4). Packaging materials may include plastic bags tightened with rubber bands for local market, plastic bag under vacuum and heat seal, tin cans with easy open lids, and retort pouch for thermal processing. Problems in leaf mustard pickle processing. The main problem of leaf mustard pickle production is the quality of raw material, especially during the rainy season. Leaf mustards produced in the rainy season develop a soft texture in contrast to mustards produced in winter. Some processors solve this problem by adding a certain chemical during the pickling process.

Figure 2. Leaf mustard pickle displayed in wet market.

Figure 3. Salted and dried leaf mustard pickle.


Figure 4. Different packaging materials for leaf mustard pickle in a

supermarket.

Drying Technologies

Dehydration or drying is the simplest and most natural form of food processing. It preserves fresh produce by removing most of its free water. Reducing the water content of the produce slows the rate of respiration, enzymatic action and overall deterioration rate, making the product less susceptible to decay and facilitating transport and long-term storage. While all vegetables can be dried, not all would be of high quality and good taste when dried. The vegetables can dry naturally in the sun (direct solar drying), via solar assisted methods (indirect solar drying), or with added ventilation and heat to speed the process (electric, gas, diesel, or solar cell powered drier). Drying in the sun is the least expensive method, and quite viable if the climate is hot and dry during harvest time. However, it is the slowest method and often results in products of lower overall quality. Pre-drying treatments, such as steam or boiling water blanching and ascorbic acid dips, can help in reducing losses of flavor, color and nutritional quality during the drying process. Value can be added to dried vegetables by enhancing flavor during drying, such as by adding spices. In Thailand, drying is done for leafy vegetables, particularly herbs and spices. Prior to drying and to improve quality of the dried product, the following operations are done:


1. Washing with clean and good quality water. 2. Removing inedible parts. 3. Cutting or slicing into small pieces to reduce drying time,

thereby minimizing loss of taste and texture quality attributes.

4. For some vegetables, blanching in boiling water or steam. Blanching is a short heat treatment, which ends certain enzymatic reactions in the fresh product. Blanching decreases the microbial population presents on the surface of fresh produce and helps retain bright color, good texture, and fresh flavor after processing. Steam blanching usually takes longer time but results in less loss of vitamins than boiling water blanching.

5. Cooling the blanched produce using cold water. Figure 5 shows a schematic presentation of generic heated air-drying. In general, an ambient air is heated and the heated air is brought into contact with food to remove moisture. When the air passes through the heater, the temperature of the air increases and the relative humidity decreases. The hot air will then pass through a bed of moist food and gives up heat that is used to evaporate free water from the food. Leafy vegetables and other agricultural produce are usually dried to below 10% moisture. Figure 6 illustrates the general procedure in drying vegetables. Solar drying The simplest method for solar drying is to lay produce directly upon a flat black surface and allow the sun and wind to dry the crop. Solar drying works best in a hot and dry climate. When drying produce in the sun, the produce is exposed to the sun for the first 2-3 days, and then transferred to a ventilated shady spot to complete drying. In locations with a high relative humidity, solar drying may take too long to produce a high quality product. Simple solar dryers can be made from trays of screen material propped upon wooden or concrete blocks to allow air to circulate under the produce, protecting it from insects and birds while drying. More complex models of solar dryers have glass or clear plastic windows that cover the produce, providing some protection from insects while capturing more of the heat of the sun. To improve drying efficiency, some sort of structure must be used to


capture solar radiation. Figures 7, 8 and 9 are examples of solar dryers developed and commercially used in Thailand. Oven drying If the weather does not permit solar drying, vegetables can be dried in a large gas or electric oven. Drying time can be reduced if ventilation is increased by using a small fan placed outside the oven. Rotating the tray every 3-4 hours within the oven and turning the produce occasionally promotes uniform drying. Packaging dried vegetables The dried products can be packed in airtight jars, plastic or glass bottles, or plastic bags. The container should be filled with the dried produce as full as possible to remove air before sealing. Heat-sealing or vacuum-sealing plastic bags can further extend shelf life of the dried product. The packed produce should be kept in a cool, dark and dry place.

Figure 5. A schematic diagram of hot air drying.


Receiving raw material

Product storage

Washing

Cutting

Pre-treatment

Drying

Packing

Finished product storage

Figure 6. General flow diagram for a vegetable drying operation.

Figure 7. Tunnel solar dryer developed by Solar Power Research, Silapakorn University, Thailand.


Figure 8. Commercial solar dryer developed by Department of Food Engineering, Mahasarakham University, Thailand for drying

white mulberry leaves.

Figure 9. Solar greenhouse dryer developed by Solar Power Research,

Silapakorn University, Thailand.

References

Division of Food Science. 2001. Food Production. Sokhothai Thummatiraj Open University Press, Thailand. 429 p. (in Thai)

Hui, Y.H., Ghazala, S., Graham, D.M., Murrell, K.D. and Nip, W.K. 2004. Handbook of Vegetable Preservation and Processing. Marcel Dekker, Inc., USA, 739 p.

Kitinoja, L. and Gorny, J.R. 1999. Postharvest technology for small-scale produce marketers: Economic opportunities, quality and food safety. Postharvest Horticulture Series No. 21. pp. 13.1-13.20.

Romnukul, P. 2002. Food Preservation. Odian Store Publishing, Thailand. 222 p. (in Thai)


Thai Industrial Standard Institute No. 69-2523. 1980. Standard of canned leaf mustard pickle. Ministry of Industry, Thailand. (in Thai)

Solar Power Thailand. 2007. http://www.thaisolarpower.com/index-thai.htm


Processing Technologies for Leafy Vegetables in the Philippines and Other

Parts of the World

Lemuel M. Diamante, Ph.D. Department of Food Science and Technology

Visayas State University Visca, Baybay, Leyte, Philippines

Introduction Leafy vegetables will deteriorate in quality within a few hours after harvesting, especially in tropical countries. Product quality deterioration can be slowed if cold storage facilities are available; even so, leafy vegetables can be stored only for a few days. If the volume of production of leafy vegetables is limited, then the harvest can be absorbed easily by the fresh market. However, if the harvest is bountiful, then there is a need to look for alternative processing technologies to prolong the availability of these vegetables. Processing into salted, pickled/fermented, dried, canned/bottled or frozen products are possible ways of extending the supply of leafy vegetables. Salting and pickling/fermenting leafy vegetables are the simplest processing methods because they do not require sophisticated equipment. However, the shelf life of a salted and pickled/fermented vegetable is limited to several days to a few weeks. To increase the shelf life of the salted and pickled/fermented vegetable for several months, bottling with heat processing is usually employed. Bottling/canning with heat processing and drying of leafy vegetables usually require the use of sophisticated and expensive equipment, but the quality of the resulting products approximates fresh produce, and the processed vegetables have shelf lives of several months. Canned/bottled and dried vegetables are stable at ambient conditions in contrast to frozen vegetables, which need low temperature storage and transport. This paper describes processing technologies in the Philippines and elsewhere and focuses on simple and inexpensive techniques. Introductory information on some factors to be considered in processing leafy vegetables is also presented.


Commodity Considerations Leafy vegetables are low in acid and sugar compared with most fruits and they vary in processing requirements for salting, pickling/fermenting, drying, canning/bottling, and freezing. For example, salt is added to pickled/fermented leafy vegetables to promote the growth of lactic acid bacteria, which eventually give the characteristic sourness to the product. Leafy vegetables need to be blanched (with water or steam) prior to drying, canning/bottling, or freezing. The purpose of blanching is to inactivate the enzymes catalase and peroxidase, which cause deterioration of vegetables during further processing. Blanching must be properly done to preserve the green color (chlorophyll), otherwise chlorophyll is broken down to phaeophytin, which imparts brown color to overblanched vegetables. Dehydrated leafy vegetables usually are dried to very low moisture (5% or less) to slow deterioration during subsequent storage. Canned leafy vegetables are processed with severe heat processing (above 100oC) because of their low acidity compared with most canned fruits, which are acidic and thereby require temperatures lower than 100oC. There is little difference in processing requirements for fruits and vegetables with respect to freezing.

Pre-processing Operations Before the leafy vegetable is processed, a number of operations usually are done, such as washing, cutting, and blanching.

Washing

Vegetables may be washed with water in three different ways: soaking, washing by agitation, and spraying. Washing vegetables with water can be manual or mechanized, depending upon the scale of operation. Soaking is not in itself an effective means of removing dirt, but it is useful as a preliminary treatment to washing by spray or agitation. If the vegetables are agitated in water, the efficiency of the soaking process is greatly enhanced. Washing by means of water spray is by far the most satisfactory method. Vegetables that are heavily contaminated with soil or other objectionable material should first be soaked thoroughly to loosen adhering soil before washing under sprays. The efficiency of a spray of water for washing depends upon the pressure of the water, its volume and also the distance of the spray nozzle from the vegetable to be washed. Spray washer pressures vary between 60 to 200 psi. The process removes most of the soil and many of the insects from the leaves.


Cutting Leafy vegetables require different cutting methods. For example, small cabbage heads are cut into sections (slicing) ready for blanching and canning. However when cabbage is to be used for pickling/fermenting and drying, fine shredding (1/32 to ¼ inch wide) may be necessary. Generally when the leafy vegetables readily soften after blanching, there is no need for cutting or shredding for further processing like pickling/fermenting, drying, or canning. In spinach harvested by cutting the stem just above the ground level, trimming is no longer necessary since it is already in the form ready for further processing. Blanching Leafy vegetables must be heated to a minimal temperature to inactivate natural enzymes before processing or storing (even when processed to frozen product). This special heat treatment to inactivate enzymes is known as blanching. Blanching is not indiscriminate heating. Too little is ineffective, and too much damages vegetables by excessive cooking, especially when the fresh character of the vegetable is to be preserved by further processing. Two of the more heat-resistant enzymes in vegetables are catalase and peroxidase. If these are destroyed, then other enzymes that contribute to deterioration also will be inactivated. Effective heat treatments for inactivating catalase and peroxidase in different vegetables are known, and sensitive chemical tests have been developed to detect the amounts of these enzymes that might survive the blanching treatment. Cabbage for canning is water-blanched at 100oC for 1-1.5 minutes while cabbage for drying is steam-blanched for about 4-5 minutes. Spinach for canning is water-blanched at 76.7oC for about 6 minutes or at 100oC for 1.5 minutes while spinach for drying is steam-blanched for about 3-5 minutes. For other leafy vegetables, blanching treatment can be established experimentally prior to commercial test. For other leafy vegetables such as Chinese kale and Chinese mustard, blanching may be done in 100oC water for about 1.5 minutes or by steaming for 3-5 minutes.

Salting Technology Salting is done to draw water from the vegetables, impart a salty taste, inhibit or kill some of the microorganisms on the vegetables, and permit the survival of useful microorganisms. Useful microorganisms produce acids and flavor compounds by fermentation of sugars in the vegetables.


A salting technology for Chinese cabbage was developed in Australia to supply the Japanese market with a raw material for pickled vegetable (Thompson et al., 2001). This was done to avoid the use of complex packaging and storage requirements for live, fresh product. The value of whole, fresh vegetables often does not justify the use of quicker, but far more expensive, air transit. The salted Chinese cabbage produced by this technology conformed to Japanese market requirements and trial export shipments were well received. The technique involves the following procedure:

1. Cabbages are cooled 5oC, and overmature and damaged wrapper leaves are removed.

2. The cabbages are cut into half longitudinally through the stem and

leaf petioles, but not the majority of leaf-blade material.

3. The halves are torn apart and immersed for 5 minutes in a 200 to 300 ppm sodium hypochlorite solution at 5oC.

4. Following disinfestation, the halves are rinsed in 5oC tap water and

shaken to remove excess water before transfer to salting tubs (inner tub dimensions: length-upper 56 cm, base 52 cm; width-upper 36.5 cm, base 32.5 cm; depth-20 cm).

5. During packing and layering into tubs, salt is sprinkled onto the

stem/leaf-petiole area at the rate of 5% by weight of the cabbage.

6. 5% salt solution at 5oC is added to tubs at the rate of 15% cabbage weight.

7. Cabbages are placed under pressure with surface weight for 16 hours

at an air temperature of either 4oC or ambient (i.e. 15o to 25oC).

a. The pressure employed at 4oC is 175% of total cabbage weight per tub, or approximately 1.2 kPa pressure.

b. If higher room temperatures are used, the pressure should be

higher, approximately 1.6 kPa (processors can determine if low temperature or high pressure is easier to achieve in their factory).


8. After 16 hours, 25% of surface weight is removed and add approximately 10% (by cabbage weight) additional volume of salt solution is added.

9. After 4 days, the salt solution is drained and the cabbage halves are

vacuum-sealed in barrier-film bags. The product is now ready for immediate consumption or additional processing. Otherwise, storage should be continued at 4oC. The abovementioned salting technology could be adapted by Asian countries that have a competitive edge in serving international markets such as Japan and South Korea.

Pickling and Fermentation Technologies Pickled vegetables may be defined as a food to which an edible acid, for example, lactic acid or acetic acid in the form of vinegar, has been added. Fermented vegetables are foods in which the acid is produced from sugar in the food product by the fermentation of lactic acid bacteria. Nearly all vegetable material may be fermented by lactic acid bacteria. They contain sugars and are nutritionally adequate as substrate for growth of the lactic acid bacteria and other microorganisms. Relatively few species of bacteria are responsible for the fermentation of the majority of vegetable products. They develop in a natural sequence of species; the relative role of each species is governed primarily by environmental conditions. Vegetable fermentation is initiated by the bacterial species Leuconostoc mesenteroides, which imparts desirable flavors derived from the acids, alcohol and other products of fermentation. It apparently produces conditions favorable to growth of other lactic acid bacteria in the growth sequence. This is followed by Lactobacillus brevis, Pediococcus cerevisiae, and Lactobacillus plantarum. The environmental conditions, numbers and kinds of organisms present, cleanliness, salt concentration and distribution, temperature, and covering will influence the course of fermentation. Fermented mustard processing Mustard leaves for fermentation are first washed very well and the roots and old leaves are removed. Salt is then sprinkled on the leaves to induce wilting. For a kilogram of mustard leaves, boil 1 cup of rice water (from washing)


with ¼ cup salt and cool. The wilted mustard leaves are placed in a jar and the rice water washing mixture is added. Weights are placed on the leaves so that they are thoroughly submerged in the salt solution and stored at room temperature. After a week or so, the fermented mustard leaves should be sour. Figure 1 presents the process flow for producing pickled mustard leaves. Pickled cabbage processing Pickling cabbage may first involve shredding to produce 1/32 inch leaf shreds. The shreds are then acidified with citric acid and/or vinegar to about 0.5-0.7% acid expressed as lactic acid, sweetened to a desirable degree (5-10% added sugar), and heated in boiling water to attain a closing temperature of 74-77oC. The usual procedure is to place the acid-sugar solution in water in the bottom of each jar and then add the blanched shredded cabbage to fill the jar. Heat processing of the jars of product as mentioned earlier and cooling the jars using tap water follow. Figure 2 shows the process flow for pickled cabbage production. Sauerkraut production Sauerkraut is originally a German fermented cabbage and was historically prepared at home in large batches as a way of storing food for the winter. The process starts by harvesting cabbages at proper maturity. The solid white heads are trimmed to remove green, broken, and dirty leaves. The core is removed and the cabbage is sliced to about 1/32 inch wide, 2.25% salt is added, and the shredded cabbage is packed into tanks. Brine begins to form shortly after shreds are salted, and when the tank is full there is sufficient brine present. The temperature of the shredded cabbage in the tank must be kept at about 18 to 23oC (65 to 73oF) to produce sauerkraut with superior flavor, color, and ascorbic acid content. The fermentation of many vegetables and vegetable blends is similar to that of sauerkraut. Figure 3 illustrates the process flow for sauerkraut production.


Harvested mustard Washing Roots/old leaves removed Add salt on the leaves Cook rice water with salt Place wilted leaves in jar ←← Cooled salt solution Cover jar tightly (air tight) Ferment (duration varies) Fermented mustard leaves

Figure 1. Process flow for producing fermented mustard leaves.

Cabbage head Remove green (wrapper), broken and dirty leaves Remove core Shredding Acid-sugar solution Cabbage shreds →→→ Bottling cabbage shreds in solution Heat-process in boiling water Pickled cabbage

Figure 2. Process flow for producing pickled cabbage.


Cabbage head

Trim green, broken and dirty leaves

Remove core

Shredding

Add salt on the shreds

Place shreds in a jar

Cover jar tightly (airtight)

Ferment

Sauerkraut

Figure 3. Process flow for sauerkraut production. Kimchi production Kimchi is a Korean fermented Chinese cabbage. The cabbage is usually sliced thicker than the European counterpart (sauerkraut). The Koreans ferment the cabbage in enormous quantities. The cabbage is packed into huge earthenware jars, which are then buried in the ground up to the neck and the lids are covered with straw until the Kimchi is needed. Kimchi almost always includes hot pepper, usually dried and either ground or crushed into flakes. Because the ground, dried hot pepper sold in Korean markets is generally fairly mild, generous quantities are usually used. Table 1 shows the recipe for Kimchi production that would yield 1.5 quarts of the product. Figure 4 presents the flow diagram of the production process. Figure 5 shows finished Kimchi in different presentations and packaging.


Table 1. Sample recipe for Kimchi production. Particular Description

A. Composition 3 tablespoons plus 1 teaspoon pickling salt 6 cups water 2 lbs Chinese cabbage (Napa), cut into 2-inch squares 6 scallions, cut into 2-inch lengths, then slivered 1 1/2 tablespoons minced fresh ginger 2 tablespoons ground dried hot pepper (or other mildly hot ground red pepper) 1 teaspoon sugar

B. Process 1. Dissolve the 3 tablespoons salt in water. Put the cabbage into a large bowl, a crock, or a nonreactive pot, and pour the brine over it. Weight the cabbage down with a plate. Let the cabbage stand for 12 hours.

2. Drain cabbage, reserving the brine. Mix the cabbage with the remaining ingredients, including the 1 teaspoon salt. Pack the mixture into a 2-quart jar. Pour enough of the reserved brine over the cabbage to cover it. Push a freezer bag into the mouth of the jar, and pour the remaining brine into the bag. Seal the bag. Let the Kimchi ferment in a cool place, at a temperature no higher than 20oC (68°F), for 3 to 6 days, until the Kimchi is as sour as you like.

3. Remove the brine bag, and cap the jar tightly. Store Kimchi in the refrigerator, where it will keep for months.


Chinese cabbage Remove green, broken, and dirty leaves Remove core Slice Dissolve salt in water Cabbage slices→→→ Mix cabbage slices in a jar Cover jar tightly Drain the brine solution Other ingredients→→→ Mix cabbage with other ingredients Ferment Kimchi

Figure 4. Process flow for Kimchi production.

Figure 5. Kimchi products from Chinese cabbage.


Drying and Dehydration Technologies Vegetable drying or dehydration involves the removal of nearly all of the water normally present in the tissues by evaporation. Drying is a general term for water removal from foods whether using natural means (sun drying) or mechanical means (artificial dryers). Dehydration is the process of water removal from foods using mechanical dryers. Since vegetables need to be dried to very low moisture, mechanical dryers are almost always used. Vegetable dehydration has one or both of the following purposes: to preserve the perishable raw commodity against deterioration and/or to reduce the cost of packaging, handling, storing and transporting the material by converting it to a dry solid, thus reducing its weight and volume. Dehydrated vegetables are used in dry soup mixes, canned soups and sauces, frozen entrees, processed meats, baby food, dairy products, and seasoning blends. Simple dryers As most vegetables are dried to <5% moisture, sun drying has limited application. Most dehydrated vegetables are processed by the forced air drying. The common kinds of simple and low-cost vegetable dryers are the cabinet dryers of various sizes. Figure 6 shows some cabinet dryers of various sizes that can be used for vegetable dehydration. Producing dehydrated cabbage In the Philippines, dehydrated cabbage is processed by first removing the wrapper leaves and those that are damaged or discolored. Each head is then sliced into quarters and the core is removed. The quartered cabbage is sliced, shredded to ¼ inch thickness, and steamed for 4 minutes. The blanched shreds are spread on trays then dried in a cabinet dryer at 60-70oC until moisture content drops to 5-6%. The dried shreds are cooled and packed in thick polyethylene or polypropylene bags. Figure 7 illustrates the process flow for producing dehydrated cabbage. In India, blanched cabbage shreds are soaked in 3% salt plus 6% sucrose for 12-16 hours at 4oC to markedly reduce shrinkage and improve rehydration without affecting palatability besides increasing shelf life of dried product.


In China, the availability of dehydrated vegetables including dehydrated Chinese cabbage and dehydrated cabbage are electronically advertised by several companies (e.g. Xinghua Luhe Foods Co. Ltd; Anhui Technology Import and Export Co., Ltd; Zibo Weike Food Co., Ltd; Zheng Kang Food Co., Ltd., etc.). However, these companies did not publish the processing conditions for their products. Dehydrated vegetables are now commodities in the international trade and a dollar earner for the country. The different dehydrated Chinese cabbage and dehydrated cabbage are shown in Figure 8. Producing dehydrated kangkong Dehydrated kangkong in the Philippines is processed by first detaching the leaves from its stem. The leaves are blanched in boiling water with 0.02% MgO for about 3 minutes. The blanched leaves are spread on trays and then dried in a cabinet dryer at 60-70oC until 5-6% moisture. The dried leaves are cooled and packed in thick polyethylene or polypropylene bags. The dehydrated kangkong leaves can be stored for up to four months. Figure 9 shows the process flow for producing dehydrated kangkong.

Figure 6. Cabinet dryers of various sizes for vegetable dehydration.


Cabbage head

Trim green, broken, and dirty leaves

Remove core

Shredding

Blanching

Spread shreds on tray

Drying

Cooling

Packaging dehydrated cabbage

Figure 7. Process flow for dehydrated cabbage production.

Dehydrated Chinese cabbage

Dehydrated cabbage

Figure 8. Dehydrated cabbages.


Kangkong leaves

Detach leaves from stem

Blanch in water with 0.02% MgO

Spread leaves on trays

Drying

Cooling

Packaging dehydrated kangkong leaves

Figure 9. Process flow for producing dehydrated kangkong leaves.

Canning Technologies Canning is a major method of preserving foods but requires relatively high initial investment. Canning is founded on the basic premise of destruction of microorganisms by heat and prevention of contamination. It has been proven that bacterial cells and spores are destroyed at a constant uniform rate by heat. This rate is characteristic for a given microorganism and for a given food in which it is heated. The constant is referred to as the specific heat resistance of a microorganism. In conventional canning, the food is placed inside containers, the air is removed by vacuum or exhausting, and the cans are hermetically sealed. The cans are placed in a retort and sterilized with steam as shown in Figure 10. The rate at which heat penetrates into the product in the can must be measured from the slowest heating part of the can. These data are then integrated with the thermal resistance constants of the target microorganism and a process time is calculated. The containers used in commercial canning consist primarily of enamel-coated steel, tin-coated steel, and glass. Plastic containers and other flexible packaging materials with laminated layers of different functional properties for protecting the food and suitable for heat processing have been used recently. For products that are more corrosive to tin, there are a variety of lacquers or coatings to apply over the tin layer, giving extra protection. Many containers are made of aluminum plate coated with epoxy resin.


Vegetables differ from fruits in chemical composition and therefore require different canning conditions. The acidity of vegetables is generally much lower than that of fruits, and they may contain more of the heat-resistant soil organisms than fruits. Many vegetables require more cooking than fruits to develop their most desirable flavor and texture. For these reasons canned vegetables in general require more severe processing than fruits. Cabbage canning Small cabbage heads are cut into sections and blanched at 100oC for 1-1.5 minutes or until soft. The cabbage while still hot is filled into cans and hot 2% brine is added. For No. 2½ cans (401 x 411) (4 1/32 inches diameter and 4 11/32

inches height) with an initial temperature of 60oC, the process usually takes 40 minutes at about 116oC. Figure 11 shows the process flow for cabbage canning. Canning techniques for other leafy vegetables Similar canning procedure is usually followed for other leafy vegetables as shown in Figure 11. Differences may lie only on the temperature and time of heating the canned produce. For spinach leaves, for example, the leaves are first thoroughly washed and then sorted out to remove defective leaves, weeds and trash. The leaves are blanched in 77oC water for about 6 minutes. While still hot, the blanched leaves are packed into cans but not too compact and hot 2% brine is added. For No. 2 ½ cans (401 x 411) with an initial temperature of 60oC, the process takes about 95 minutes at 116oC.

Figure 10. Vertical and horizontal retorts used in the canned food

industry in the United States.


Cabbage head

Trim green, broken, and dirty leaves

Remove

Cut into sections

Blanching

Place blanched cabbage in cans → 2% Brine

Heat processing

Cooling

Canned cabbage

Figure 11. Process flow for producing canned cabbage.

Summary Processing is an important value-addition activity that could solve the perishability problem of leafy vegetables, increase the availability and marketability of the product, and improve farm productivity and profitability. In many developing countries, such as those in the Greater Mekong Subregion, leafy vegetable production and processing are dominated by small-scale farmers and processors. Thus, processing technologies to be introduced must be simple and low-cost but should not compromise product quality and marketability. A range of simple processing technologies for leafy vegetables is described, such as salting, fermentation, and dehydration technologies. Other processing techniques, such as freezing and canning, are relatively expensive but could be employed by small processors if they can organize among themselves to form a group (e.g. cooperative) and are given support by relevant government institutions and other development agencies.

References Cruess, W.V. 1958. Commercial Fruit and Vegetable Products. McGraw-Hill Book

Company, New York. pp. 42-55.


De Leon, S.Y., Bravo, O.C. and Martinez, L.O. 1988. Fruits and Vegetables Dehydration Manual. National Book Store Inc., Diliman, Quezon City. p. 204.

De Leon, S.Y., and Guzman, M.P. 1982. Preservation of Philippine Foods. Phoenix Publishing House, Inc., Quezon City. p. 107.

Diamante, L.M. 2006. Dehydration of food products. Resource Unit in Food Processing and Preservation. Visayas State University (VSU), Visca, Leyte, Philippines. 35 pp.

Diamante, L.M. 2006. Heat processing of food products. Resource Unit in Food Processing and Preservation. VSU, Visca, Leyte, Philippines. 30 pp.

Diamante, L.M. 2006. Pickling and fermentation of food products. Resource Unit in Food Processing and Preservation. VSU, Visca, Leyte, Philippines. 25 pp.

Diamante, L.M. 1998. Dehydration of food products (Module 13). Training Modules on Capability Building and Curriculum Enhancement on Agri-Products Processing for TechVoc Teachers. TESDA-SSDF/ViSCA, Leyte, Philippines. 32 pp.

Diamante. L.M. 1996. Development of a combination agrowastes and solar dryer for processing of fruit and vegetable products. In: F.B. Sotto, D.T. Dy and J.G. Young, eds., Proceedings of the Conference on Environmental Research and Resources Management in the Visayas and Mindanao Regions of the Philippines. pp. 122-132.

Jayaraman, K.S. and Das Gupta, D.K. 1992. Dehydration of fruits and vegetables - Recent developments in principles and techniques. Drying Technology. 10(1):1-50.

Luh, B.S. 1992. Vegetable processing. In: Y.H. Hui, ed., Encyclopedia of Food Science and Technology. John Wiley & Sons Inc., New York. pp. 2662-2669.

Luh, B.S. and Kean, C.E. 1975. Canning of vegetables. In: B.S. Luh and J. Woodroof, eds., Commercial Vegetable Processing, AVI Pub. Co, Westport, Connecticut. pp.195-289.

Pederson, C.S. 1975. Pickles and sauerkraut. In: B.S. Luh and J. Woodroof, eds., Commercial Vegetable Processing, AVI Pub. Co, Westport, Connecticut. pp.457-490.

Hua, J. and Huang, C. 1992. Vegetable pickling & fermenting. In: Y.H. Hui, ed, Encyclopedia of Food Science and Technology. John Wiley & Sons Inc., New York. pp. 2677-2680.

Potter, N. and Hotchkiss, J.H. 1995. Food Science. Chapman & Hall, New York. pp.418-442.

Somogyi, L.P. 1992. Vegetable dehydration. In Encyclopedia of Food Science and Technology (Y.H. Hui, ed.). John Wiley & Sons, Inc. New York. pp. 2657-2662.

Thompson, G., Morgan, W., Winkler, S., Chew, M., Frisina, C. and Jaeger, J. 2001. Diversifying Asian vegetable Markets. Rural Industries Research and Development Corporation, Barton, ACT. 17 pp.

http://www.fabulousfoods.com/bios/ (visited September 30, 2007)


Processing Technologies for Leafy Vegetables Outside GMS

Sasitorn Tonchitpakdee, Ph.D.

Department of Food Science and Technology, Faculty of Agro-industry, Kasetsart University

Bangkok, Thailand

Introduction Leafy vegetables, also called potherbs, greens, or leafy greens, are plant leaves eaten as a vegetable, sometimes accompanied by tender petioles and shoots. There are several hundreds species of plants with edible leaves. Leafy vegetables most often come from short-lived herbaceous plants such as lettuce and spinach. They are generally low in calories and fats, high in dietary fiber, minerals (iron and calcium), and protein per calorie. They also contain high amount of phytochemicals such as vitamin C, vitamin A, lutein, folic acid, and phenolic compounds. Examples of leafy vegetables are bok choy, brussels sprouts, collards, cabbage, Swiss chard, lettuce (iceberg, romaine), kale, mustard greens, spinach, and watercress. Leafy vegetables can be eaten raw or cooked. They can be processed into different products such as minimally processed, canned, fermented, frozen, and dehydrated products. Information provided in this paper is about simple processing techniques for leafy vegetable processed products, which are be found in countries outside the Greater Mekong Subregion.

Fermented Leafy Vegetables Sauerkraut Sauerkraut or kraut is a fermented cabbage (Brassica oleracea var. capitata L) which is prepared from sound, well-matured heads. The five commercial varieties of cabbages used for sauerkraut production are Dutchmaster Ferry Morse 6201, King Cole, Roundup, Glory 61, and Large Glory. Cabbages with 24% total sugar are suitable for sauerkraut production. Generally, good quality raw material contains up to 30-60 mg/100 g of vitamin C. Sauerkraut can be prepared as whole or shredded style. However, shredded sauerkraut is more common for the industry due to its good quality and uniform fermentation.


The sauerkraut processing flow is shown in Figure 1. After delivery, cabbages are transported via conveyer to the coring machine. Then the cored head is trimmed (removing outer leaves and bad spots) and cut/shredded before transport to fermentation vat. Salt (2-3%) is added evenly as the shredded cabbage is distributed in the vat. This allows the product to be cured by natural fermentation. Immediately after adding salt, juice is released from the cabbage. This “early brine” may be withdrawn from the vat to assure a maximum filling of cabbage into the vat. After the vat is filled, it is covered with a plastic sheet that is weighed with water. After four or more weeks, the fermentation is considered complete, when the finished product contains not less than 1.5% of acid, expressed as lactic acid. Fermentation temperature is at 20-25°C in the first phase and needs to be lowered to 14-18°C. In the early stage of fermentation, most of the lactic acid bacteria are heterofermentative (gas-forming) species such as Leuconostoc mesenteroides. The carbon dioxide creates an anaerobic environment that promotes the desirable lactic acid bacteria. After eight days of fermentation, most of lactic acid bacteria are homofermentative (nongas-forming) species such as Lactobcillus plantarum. Other lactic acid bacteria in sauerkraut production are Lactobcillus brevis and Pediococcus cerevisiae.

Cabbage

Temporary storage

Removal of external leaves

Coring/Trimming

Cutting/Shredding

Salt addition

Fermentation

Storage

Figure 1. Flow chart of sauerkraut processing.


Korean baechu cabbage Trimming and cutting Washing Brining

Red pepper powder, garlic, radish, ginger, salted-pickle seafoods, green onion, sugar, etc.

Rinsing

Draining

Brined Cabbage

Stuffing/Mixing

Packaging

Fermentation

baechu kimchi

Figure 2. Flow chart for Baechu Kimchi processing.

Table 1. Recipe, Baechu Kimchi.

----------------------------------------------------------------- Raw ingredients Weight ratio (%) ----------------------------------------------------------------- Korean baechu cabbage 100 Radish 13 Green onion 2.0 Red pepper powder 3.5 Garlic 1.4 Fermentation anchovy juice 2.2 ----------------------------------------------------------------

Shelf life of the finished product after completion of fermentation depends on the storage temperature. The finished product shelf life/storage time at a temperature of about 15°C is estimated at six months. At temperatures not exceeding 20°C, the storage time could be estimated at 2-3 months. The product maybe canned using sufficient thermal processing to assure preservation in hermetically sealed containers (cans, jars, or flexible pouches), or it may be packaged in sealed containers and preserved with or without the addition of sodium benzoate or any other ingredient approved by the FDA.


At small scale and in traditional processing, shredded sauerkraut can be obtained by using simple available glass or rigid plastic receptacles. At home, this process can use glass jars and/or local/traditional pottery receptacles from a minimum size of 2-3 kg up to the available/practical sizes (better limited to 10-15 kg). For whole sauerkraut production, prepared whole cabbages are put into fermentation vats and 5-6% salt concentration brine is poured on top. The fermentation conditions are the same as for shredded sauerkraut. To assure a uniform fermentation and to avoid a strict anaerobic (butyric) fermentation it is necessary to apply "aeration" step (every 2-3 days at the beginning of the fermentation, and then every 5-7 days). In some countries, sauerkraut juice is produced for its dietetic value (lactic acid and vitamin C content) and its refreshing taste. The juice, the result of the fermentation of lactic acid from cabbage, mainly from sliced sauerkraut, is used. The juice must be the result of a normal lactic fermentation, i.e. without butyric fermentation or other deterioration. A good quality juice must have an acidity of 1.4% lactic acid and a content of maximum 2.5% salt. This is obtained by the mixing of various sauerkraut qualities. The collected juice (from sauerkraut production) is heated slightly to eliminate CO2 gas and to obtain protein coagulation. Filtration of juice is the next step, followed by filling in container, closing and pasteurization at 75-80°C for 4-5 minutes. Kimchi (pickled cabbage) Kimchi is a traditional fermented food product in Korea. It is probably the most important processed food product in Korea and it is eaten at most mealtimes. Production is estimated at over one million tons, mainly at household level. Daily consumption is estimated at 150 to 250 grams per person. There are almost 200 types of kimchi available in the market. However, the most popular type of kimchi is baechu kimchi, which is made from cabbage. Baechu kimchi can be prepared using whole cabbage (tongbaechu kimchi) or chopped/cut cabbage (matbaechu kimchi). Other types of kimchi are made from radish, cucumber, leek, spinach, green pepper, etc. This section refers to kimchi produced from cabbage. Essential processing steps that can affect quality of kimchi are selection and formulation of raw ingredients, salting, rinsing and draining, pretreatment of sub-ingredients, mixing process, placing in crock (fermentation vessel), and fermentation (Fig. 2). Good quality of Korean baechu cabbage (Brasica campestris var. pekinensis) (known also as Chinese cabbage), with light-green colored soft leaves and compact structures with no defects, are required for production of kimchi. After grading and washing, the cabbage is cut lengthwise into 2 to 4 parts and


treated with dry salt for several hours or with 10% brine for 10 hr. For chopped matbaechu kimchi, the cabbage is cut into 3-5 cm pieces and macerated in 8-15% salt solution for 2-7 hours. Maceration is the most important step for taste, texture, fermentation, and preservation. The macerated cabbage is rinsed several times with fresh water to remove excess salt and drained to remove extra water. A mixture of spices and other ingredients (Table 1) are packed between layers of cabbage leaves. The stuffed cabbages are placed in a jar (crock) to allow facultative anaerobic condition for fermentation. Traditionally, the crock is buried underground to maintain consistent low temperature. Kimchi fermentation is carried out by various microorganisms present in the raw materials and ingredients used, especially lactic acid bacteria. Among the 200 bacteria isolated from kimchi, the important microorganisms in fermentation are Lactobacillus plantarum L. Brevis, Streptococcus faecalis, Leuconostoc mesenteroides, and Pediococcus pentosaceus. After fermentation, the product can be left to mature for several weeks if refrigeration is available. If stored under warm conditions, the kimchi deteriorates rapidly. To assure good quality of kimchi, the final salt concentration of the product is adjusted to 2.2-3.0% (w/w).

Fermented mustard leaf

Fermented mustard leaf or leaf mustard pickle or Pak-gard-dong (Fig. 3) is a well-known indigenous fermented food product found in many Asian countries such as China, Taiwan, and Thailand. In Taiwan, most of harvested leaf mustards are dry-salted in wells or vats for fermentation to prepare the pickle product. After fermentation, the yellowish pickles with crispy texture and pickle flavor are called Hum-choy.

Figure 3. Fermented mustard leaf.

General processing steps of leaf mustard pickles are shown in Figure 6. The mature leaf mustard are washed, cut, and wilted in the sun for a day. Then they are trimmed and shipped to fermentation wells or vats. Prior to


deposition of the first layer of leaf mustard in an upright position, dry salt is spread at the base of well. For the following layer, the leaf mustard is deposited at inverted position and each layer is spread with dry salt and pressed tightly. At the top of a well, the leaf mustard is covered with a heavy-duty plastic film and weights. After three days, water is drawn out of vegetable tissue and the level of leaf mustard is lowered. Further deposition of leaf mustard and salt are repeated 2 or 3 times and finally covered and sealed with a heavy-duty plastic film and pressed with stones for long term fermentation (2-6 months). Microorganisms associated with the fermentation include lactic acid bacteria, Lactobacillus spp., Pediococcus spp. and Leuconostoc mesenteroides. The products can be marketed for consumer demand or hermetically sealed in sterilized cans or pouches for local and overseas sales. Leaf mustard pickles can be used as raw material for fu-choy and mei-kan-choy production (Fig. 4). Fu-choy is a product with unique flavor and aroma that has an in-container secondary fermentation. For fu-choy production, fermented mustard leaf are partially dried (sun drying), then the stems and the inner leaves are cut into thin strips and packed tightly in glass bottles or other types of containers. The neck of container is filled with the partially dried leaves originating from outer leaves and followed by sealing. The bottles or jars undergo secondary fermentation in a bottom-up position for 2-3 months. The products are stable at ambient temperature with shelf life several months to a year. Mei-kan-choy, an intermediate moisture fermented product, is usually made from the sun-dried outer leaves of leaf mustard pickle.

The mature leaf mustard

Washing/cutting

Sun-drying (1 day)

Trimming and shipping to fermentation vats

Spreading dry salt at the base of vats

(A) Deposition of leaf mustard (upright position)

(B) Spreading dry salt onto leaf mustard (9-15% w/w)

(C) Deposition of leaf mustard (inverted position)

(D) Coverage with plastic film and weights (3 days)

Repeat (A)-(D) 2 or 3 times

Coverage and sealing with heavy-duty plastic film and weights


Fermentation (2-6 months)

Leaf mustard pickles

Partially dried (sun drying)

Inner parts of leafs Outer parts of leaf

Cutting into strips Further sun drying

Packing into jars or bottle Wrap wilted leaves into balls

Pressing/capping /sealing Packing in plastic bag

Aging bottom up (2 months) Mei-kan-choy Fu-choy

Figure 4. Flow chart of leaf mustard pickle processing. Other pickled leafy vegetables There are many other brine-pickled leafy vegetables around the world such as Pak-sian-dong, a popular pickled leafy vegetable Pak Sian (Gynadropsis pentaphylla) in Thailand, Sayur asin, a fermented wilted mustard cabbage (Brassica juncea) from Indonesia, which is also known as kiam chai in Thailand, and kiam chaye in Malaysia, and Gundruk (pickled leafy vegetable), a non-salted lactic acid bacteria products of Nepal.

Dried/Dehydrated Leafy Vegetables Dehydrated spinach Large-leafed spinach is selected as raw material. The older leaves and roots are trimmed off. After thorough washing, spinach is loaded onto trays and subsequently onto carts for dehydration. The drying temperature should be


maintained at 80C. The dehydration time is about 4 hours. After dehydration, the moisture of dehydrated spinach should be below 6.5%. Dehydrated cabbage Large cabbages with good quality (soluble solid not less than 4 Brix) are selected as raw material. Outside layers of the head cabbage are removed. The cabbages are then shredded and blanched in boiling water with 0.2% sodium bisulfite for 3 minutes. After that they are loaded onto trays for dehydration.

Frozen Leafy Vegetables According to USDA (product grades) and product standards (FDA), frozen leafy greens are the frozen products prepared from the clean, sound, succulent leaves and stems of plants including beet greens, collards, dandelion greens, endive, kale, mustards green, spinach, Swiss chard, turnip greens, and any other “market accepted” leafy green. The preparation processes include sorting, trimming, washing, blanching, and proper draining. The product then is frozen and maintained at proper temperature for its preservation. Any functional, optional ingredient(s) permissible under the law maybe used to acidify and/or season the product. Frozen leafy greens are available in the market in different styles such as leaf, chopped, and pureed.

Fresh-cut (Minimally processed) Leafy Vegetable "Fresh-cut produce" is defined as any fresh fruit or vegetable or any combination thereof that has been physically altered from its original form, but remains in a fresh state. Regardless of commodity, it has been trimmed, peeled, washed and cut into 100% usable product that is subsequently bagged or prepackaged to offer consumers high nutrition, convenience, and value while still maintaining freshness. Fresh-cut produce is also known as minimally processed, lightly processed, partially processed, pre-prepared, fresh processed, pre-cut, value-added products. This product provides convenience, appearance, taste, and flavor for consumers. Leafy vegetables that are available in the market as fresh-cut produce are lettuce and spinach (Fig. 5). In fresh-cut lettuce processing (Fig. 6), good quality lettuce is harvested and trimmed of outer leaves and transported to the packinghouse where it is cooled using vacuum or forced-air cooling. Lettuce heads are then graded or sorted and further trimmed before coring using a coring device in a room with low temperature (3-5°C). The cored lettuce is then conveyed to continuous-feed cutter for cutting (3 x 3 cm) or shredding (<0.5 mm). Some lettuce types


(romaine) need manual cutting. The lettuce is then washed with water with disinfectant.

Figure 5. Examples of fresh-cut (minimally processed) leafy vegetable.


Harvest ↓

Field-pack & local transport ↓

Vacuum or forced-air cooling ↓

Reception, dump, trim, and core ↓

Chop/shred/tear ↓

Wash and cool ↓

Centrifugation or other drying technique ↓

Combine different products for salad mixes ↓

Package in plastic film bags ↓

Box, palletize and store temporarily ↓

Transport to food service outlets and/or retail markets

Figure 6. Flow chart of fresh-cut lettuce processing.

Processing aids can be used to reduce browning. The lettuce is dried using centrifuges and air tunnels, and may be combined with different products for salad mixes. Final products are packed into plastic film bags, which are normally modified atmosphere packaging. Bags then go through a metal detector and conveyor to boxing and palletizing area. Temperature for temporary storage should be <5ºC (<41ºF), among which 0°C (32°F) is optimum temperature. Fresh-cut products should be transported to food service outlets and/or retail markets in pre-cooled clean trucks equipped with thermostat at <5°C (41°F). Keys to maintaining quality and extending shelf life of fresh-cut vegetable products are to use the highest quality raw material, minimize mechanical damage (use sharp knives), rinse cut surfaces, remove excess water, maintain strict sanitation, use appropriate packaging and atmosphere, and maintain product temperature at 1-2°C.

References

Battcock, M. and Azam-Ali, S. 1998. Fermented fruits and vegetables: a global perspective. FAO Agricultural Service Bulletin No. 134.

Bates, R.P., Morris, J.R. and Crandall, P.G. 2001. Principles and practices of small- and medium-scale fruit juice processing. FAO Agricultural Service Bulletin No. 146.


Cantwell, M. 2007. Fresh-cut Vegetable Products: Overview and Challenges. http://postharvest.ucdavis.edu/

Hui, Y.H., Ghazala, S., Graham, D.M., Murrell, K.D. and Nip, W.K. 2004. Handbook of vegetable preservation and processing. Marcel Dekker, Inc., USA, 739 p.


Workshop Summary Summary of processing technologies for leafy vegetables considered to be adapted and developed by Cambodia, Laos, and Vietnam teams Purpose Cambodia Lao PDR Vietnam Improved quality and shelf life of fermented leafy vegetable

Optimize fermentation process for cabbage by considering techniques from China, Myanmar, Thailand and Vietnam and on salting

Optimize fermentation process for Chinese mustard by considering techniques from China, Myanmar, Thailand and Vietnam and on salting

Optimize RIFAV fermentation technique for Chinese mustard and cabbage

Develop dehydrated leafy vegetable

Drying cabbage by solar dryer and vacuum dryer

Use of solar dryer (optional activity)

Other recommendations: Modifying the salt concentration and pH (using food-grade citric acid) is the key to improving shelf life of fermented products.


PART IV: Concluding discussion

Upland Agricultural Development in Yunnan, China

Li Yunshou, Ph.D.

Deputy Director General Agricultural Environment and Resources Research Institute

Yunnan Academy of Agricultural Sciences Kunming, Yunnan, China

Introduction Yunnan’s agriculture typifies an upland scenario. It is a mountainous and multi-ethnic province on a plateau in China with the highest altitude of 6740 m and lowest altitude of 76 m. Its natural environment is very special, the landform and physiognomy are complex, and the earth’s surface and underground are rich in resources. The geographical site of Yunnan is from 21°83′2″ to 29°15′8″ north latitude and from 97°31′39″ to 106°11′47″ east longitude. The maximal length from the east to the west is 864.9 km and the maximal length from the south to the north is 990 km. The province has a mild climate, profuse rainfall, a short frosting period per year, and a lot of sunshine. The total area of the province is 394,000 km2 or about 4.1% of the country’s total land area. The population is nearly 45 million with 26 local nationalities. The rural population accounts for 77% and the population of poverty distributed in rural areas is 10.05 million.

Brief History of Yunnan Agriculture Yunnan’s agriculture has a long history that probably dates back more than a million years ago. The discovery of Sinanthrupus yuanmouensis demonstrated that there were traces of human activities 1.7 million years ago. The social, morphological, administrative, and agricultural configuration of the province has evolved through very lengthy and complex processes. Agriculture has been influenced by inland agricultural civilizations, Yunnan people began to plow by cattle and irrigate fields in early Chin Dynasty (221-206 B.C.). After Zhuge Liang (181-234) quelled the Nanzhong during the Three Kingdoms (220-265), people were encouraged to farm, plant mulberry, rear silkworm, and mobilize garrison troops and peasants to open up wasteland and grow food grains on a large scale. Today’s Qujing Prefecture is a product of those efforts, becoming the agricultural civilization center of Yunnan. From Jin Dynasty (265-316) to the middle of Tang Dynasty (618-907), most of Yunnan was governed by Nanzhao (a local regime in ancient


China) and many advanced agricultural techniques and tools were brought in, especially from Sichuan. The political and military system of transporting prisoners and migrating garrison troops to Yunnan to reclaim fields played the most important role in the development of agriculture from the late Tang Dynasty to Ming Dynasty (1368-1644). The exchanges between Yunnan and inland China were very frequent and included agricultural techniques, tools, seeds, plant varieties, food products, and other materials. During the early period of the Qing Dynasty (1644-1840), the government took some active measures to develop Yunnan’s agriculture. However, in the late period of the Qing Dynasty (1840-1911) after the Opium War, just like the other provinces of China, Yunnan became a semifeudal and semicolonial prefecture of Britain and France. During the period, Mengzi, Manhao, Hekou, Simao, and Kunming were gradually opened as foreign commercial ports. After the 1911 revolution led by Dr. Sun Yat-sen, the Qing Dynasty was overthrown and the government proposed to re-energize industries. Yunnan’s agriculture production (tea, raw silk, tobacco, medicinal materials, etc.) developed more rapidly. However, the Japanese invasion in 1930-1940 caused great damage to the agricultural economy. Since 1949 and following the lead of inland provinces, Yunnan’s agriculture went through many different stages: requisitioning public grain to increase stores, suppressing bandits and putting down counterrevolutionaries, increasing grain yield to support the war to resist U.S. aggression and aid Korea, land reform movement, socialist transformation of agriculture, movement to form rural people’s communes, the Great Leap Forward movement, rural socialist education campaign (1963-1966), the Great Proletarian Cultural Revolution (1966-1976), restructuring of rural economic system (1979-1992), opening to the outside world, construction of socialist modernization, and socialist new village construction. In every stage, Yunnan’s agriculture developed steadily at varying degrees.

Achievements of Yunnan’s Agriculture At the end of 2005 and through the realization of the 10th Five-Year Plan (2001-2005), the total agricultural output value in Yunnan surpassed the 100 billion RMB (Renminbi or Chinese Yuan) target as it reached 106.8 billion RMB. The agricultural added value reached 65.6 billion RMB, the total yield of grain reached 15 million tons, the livestock farming output value reached 33.9 billion RMB, and the pure income of farmers reached 2042 RMB per farmer per year. These agricultural achievements laid a stable foundation of the future development of the agricultural economy. The main agricultural achievements during the 10th Five-Year Phase were:


1. Grain yield reached all-time highs in the history, and the rate of high

quality food increased by a big margin. The production of tobacco, potato, tea, sugar cane, natural rubber (oak), cut flowers, and various vegetables developed rapidly. Nearly 200 products gained the Green-Food Symbol, 280 products the Nontoxic-Food Symbol, and 272 areas recognized as nontoxic-food plant growing area.

2. The structure of agricultural production was rationalized and off-farm production, forestry, livestock farming, and fisheries were improved. The ratio of grain crops and commercial crops was nearly 70:30. Livestock farming output value accounted for 32% of the total agricultural output. The area of nontoxic-food production also increased.

3. Agricultural industries developed further and export-oriented industries expanded gradually. At the end of 2005, 2,500 agricultural enterprises realized 22.6 billion RMB of sales income. Other offshoots of agricultural industrialization included the development of super-industries, improved specialization and standardization of agricultural production, and raised the participation of farmers’ organization.

4. The town and township enterprises developed speedily and transformation of towns to cities increased by 29.5%. More than 3.5 million people were employed in the labor force in these enterprises, with added-value production of 60.8 billion RMB.

5. Farmers’ income increased steadily and livelihood burden was reduced. Many farmers were trained through the Sunshine Project and the Millions-of-Civilian-Workers Training Project, and most of the surplus trained manpower (nearly 5 million) were employed outside the province, earning a labor income of 10 billion RMB accounting for 20% of pure income of farmers per year.

6. Projects to help the poor and related regulations were implemented to improve the living standards of people living below the poverty line. The main measures were to develop agricultural industries, train and mobilize the surplus rural labor force, provide financial assistance through small loans, social assistance, and moving whole villages in poor areas to resource-rich areas suitable for human living. The government also invested more than 15 billion RMB in the “help-the-poor” financing, reducing poverty among the population from 10.22 million to 7.38 million, effecting relocation of 0.3 million families from their shanties to better homes, and increasing the school attendance rate of children to 97%.

7. Government investment increased to 47.45 billion RMB to provide rural basic infrastructures, preserve the environment, improve


farmland and irrigation systems, solve the problem of unsafe drinking water that affected 5.56 million people, and increase crop production. By the end of 2005, 83% of administrative villages had safe tap water, 98% had electricity supply, more than 98% had good roads, 92% had telephone facility, and 49.9% of the province had forest cover.

8. Scientific and democratic administration of rural public affairs maintained social stability and accelerated material and cultural progress.

9. Because of the friendly relationships and good bilateral and multilateral cooperation between China and ASEAN and other countries, membership in the WTO, formation of cooperation of Pan-Zhujiang-Delta district, and the promotion of intra- and international agricultural product markets, Yunnan’s agriculture is expected to develop more rapidly.

Emerging Challenges Many conditions favored the development of Yunnan’s agriculture, but there are challenges to confront in the future, such as the following:

integration of urban and rural economy and development of industries

enhancement of agricultural productivity without compromising the environment

development of rural and agricultural modernization

improvement of the economic and social well-being of farmers Increasing farmers’ income and reducing the income gap between rural and urban populace (the ratio of rural and urban population was 4.5:1 in 2005) are difficult challenges. The net income of rural people per year was lower than the national average. Investment in agricultural basic facilities is still insufficient and the ability to resist natural calamities is very weak. Average economic losses due to natural calamities exceeded 5 billion RMB per year. Agricultural growth is still limited and agricultural competitiveness is difficult to raise. Farmers’ cultural practices are far from being scientifically or technologically based, and rural labor migration is high. With increasing urbanization, some unpredictable and even irreversible problems such as environmental pollution and food safety problems could occur in the future. On a global scale, as part of the Greater Mekong Subregion, Yunnan is


situated in a region that can be easily influenced by trans-border developments, disease spread, and climate change.

Directions of Upland Agricultural Development in Yunnan Although Yunnan’s agriculture is more underdeveloped than that of the inland provinces, it has great potential to develop due to its unique features and strategic location. Scientific development should guide agricultural development. Developing local industries both downstream and upstream, accessing markets, increasing scientific and technological innovations, to conform and balance productive elements, and promoting rural development should led to economic prosperity and more dignified human living conditions.

Cooperation for GMS Upland Agricultural Development

Agricultural ministers of the six GMS countries (China, Cambodia, Lao PDR, Myanmar, Thailand, and Vietnam) have passed CASP to advance trans-border agricultural trade and investment, accelerate food safety and poverty reduction initiatives, reinforce the protection of the environment and sustainable use of natural resources, and open the borders to all GMS members fairly. The Asian Development Bank (ADB) has supported GMS economic cooperation projects through the years and made great efforts to coordinate minister meetings. Cooperative works among GMS partners in developing postharvest handling technologies and creating market opportunities could possibly delve into studies on the policies of rural economy and society, problems of poverty and food safety in upland regions, regional agricultural production and programming, strategic sustainable agricultural development, R&D on vegetable plants with medicinal, nutritional, pharmaceutical, and pesticidal properties, industrial processing (e.g. ethanol or diesel oil material plants), new variety breeding technology, postharvest integrated pest control (Post-IPM), studies on postharvest losses, specific PHT development, produce processing technology, substitute plant development for poppy (opium) and toxic hemp, training and technology transfer, building database for agricultural and biological resources, national and regional market research, market information development, and product and trade standardization.


Summary of General Discussion Priority postharvest problems/needs for leafy vegetables in CLV and PHT R&D interventions

PARTICULAR CAMBODIA LAO PDR

VIETNAM

Priority leafy vegetables

Common cabbage, Chinese kale

Common cabbage, Chinese/green mustard

Common cabbage, Chinese mustard, kangkong (optional: leafy pumpkin)

Problems/ needs

R&D works Problems/ needs

R&D works Problems/ needs

R&D works

Lack of storage techniques, especially during peak production

Use of EC (2 structures) in combination with other treatments to prolong shelf life

Lack of storage techniques, especially during peak production; need to extend storage life by at least 1 month

Use of EC (2 structures) in combinations with other treatments to prolong shelf life of cabbage and green mustard

Rapid wilting and yellowing of Chinese mustard and kangkong

Poor packaging leading to losses and rapid quality deterioration

Improving existing plastic film packing in common cabbage and chinese kale

Rapid wilting and yellowing of mustards

Improving existing plastic film packing in cabbage

Poor packaging leading to losses and rapid quality deterioration

Use of MAP and ethylene scrubbers to control wilting and yellowing in package and storage; improving existing plastic film packing

Fresh produce handling

Cabbage soft rot

Use of lime, alum and guava leaf extract for soft rot control

Cabbage soft rot


Cabbage soft rot


Processing Fermented products

Short shelf life of fermented cabbage

Adapt and refine RUA processing technique for cabbage

Low quality, short shelf life of fermented mustard

Adapt Vietnam technique and compare with indigenous method for Chinese mustard

Fermentation techniques for leafy vegetables not optimized

Optimize pH and salt concentration for Chinese mustard and cabbage

Dehydrated products

No drying technique for cabbage

Test solar dryer Adapt low-cost vacuum frying technique (Philippines)

Test solar dryer

Other recommendations: 1. For the problem of oversupply during production peak: proper cropping systems, understanding of market dynamics, (e.g. supply/demand, price trends), and diversifying production. 2. Training on basic principles of processing as well as postharvest handling is urged as existing knowledge of partners in Cambodia, Laos, and Vietnam is insufficient.


ANNEX: Program & Participants

Workshop on

Best Practices in Postharvest Management of Leafy Vegetables

in GMS Countries

25-27 October 2007

Army Hotel, Hanoi, Vietnam

Organizers:

AVRDC - The World Vegetable Center Research Institute of Fruits and Vegetables, Vietnam

Asian Development Bank


Scope and Objectives Postharvest technology (PHT) is crucial for vegetables to bring down product losses, improve marketing and utilization, and increase farm returns. It is of particular importance in the Greater Mekong Sub-region (GMS), one of the world’s leading vegetable producers and consumers, in which vegetable industry development is seriously constrained by high postharvest losses and poor marketing system. To help minimize these problems, the AVRDC-ADB RETA 6376 project embarks on PHT development for leafy vegetables complementing on-going initiative on fruit-vegetables. This workshop serves as an initial undertaking.

The overall goal of the workshop is to build the groundwork for future PHT R&D works for leafy vegetables in GMS. The specific objectives are to:

1. examine the needs and problems of leafy vegetable farmers and other supply chain actors in Cambodia, Lao PDR and Vietnam (CLV) and the existing country initiatives addressing those needs/problems.

2. review and document the fresh produce handling and processing technologies for leafy vegetables available in GMS and elsewhere.

3. identify PHTs to be developed and formulate the R&D details.

4. foster regional cooperation to advance the vegetable industry in GMS countries.

This workshop gathers PHT experts, key project players and other development workers in GMS to discuss and analyze the initial findings of surveys on leafy vegetable value chains in upland areas of CLV and the existing country interventions (Session 1) and exchange available experience in postharvest handling (Session 2) and processing (Session 3) of leafy vegetables, including indigenous techniques and those in commercial practice with particular emphasis on simple and low-cost innovations. Session 1 will conclude with a list of priority problems/needs to be addressed while Sessions 2 and 3, postharvest handling and processing technologies to be developed by the CLV teams, respectively. Each session will be presided by a Chair and proceedings recorded by the Rapporteur. Paper presentations will precede the workshop discussion.


Participants Main participants include RETA 6376 national coordinators and team members from Cambodia, Laos, and Vietnam, participating partners and PHT experts from China (Yunnan Province), Myanmar, and Thailand, invited experts and AVRDC scientists. Limited slots for representatives of development agencies are available subject to payment of registration fee of 150 USD that includes workshop kit and proceedings, welcome dinner, lunches and coffee breaks, and study tour. Contact: Dr. Antonio Acedo Jr. Regional Project Coordinator AVRDC-ADB Postharvest Projects PO Box 3938 Vientiane, Lao PDR Tel: +856 21 780028 Fax: +856 21 780042 Mobile: +856 20 288 3275 Email: [email protected]


Program Schedule

24 October 2007 (Wednesday) Arrival of participants

25 October 2007 (Thursday)

0830 Registration

0900 Welcome statement Director General / RIFAV

0910 Welcome statement and workshop overview

Antonio Acedo Jr / Regional Project Coordinator

0920 Introduction of participants

0930 Group picture & coffee break

Session 1: Problems and needs of leafy vegetable value chains in poverty-stricken

upland areas in CLV and available country interventions

1000 Country presentations:

Cambodia findings Mong Vanndy / KKARC

Lao PDR findings Thongsavath Chanthasombath / CMC

Vietnam findings Chu Doan Thanh / RIFAV

Sirichai Kanlayanarat / Chair 1045 Discussion and prioritization of

postharvest

problems/needs for R&D

intervention

Varit Srilaong / Rapporteur

1230 Lunch break

Session 2: Postharvest technologies for fresh leafy vegetables

1400 Paper presentations:

China experience Cheng ZongQi / YAAS

Myanmar experience Kyaw Nyein Aye /YTU

Thailand experience Sirichai Kanlayanarat / KMUTT

Experience outside GMS Antonio Acedo Jr / AVRDC-ADB PPO


Win-Win Kyi / Chair 1500 Discussion:

Chu Doan Thanh / Rapporteur

1530 Coffee break

1600 Discussion continued and identification of postharvest handling technologies to be

adapted/developed

1900 Welcome dinner

26 October 2007 (Friday)

Session 3: Processing technologies for leafy vegetables

0830 Paper presentations:

China experience Li Hong / YAAS

Myanmar experience Win Win Kyi / AVRDC-ADB PPO

Thailand experience Varit Srilaong / KMUTT

Experience outside GMS Lemuel Diamante/VSU

Sasitorn Tongchitpakdee/KU

0930 Discussion: Antonio Acedo Jr / Chair

Borarin Buntong / Rapporteur

1030 Coffee break

1100 Discussion continued and identification of processing technologies to be adapted/developed

1230 Lunch break

Li YunShou / YAAS 1330 Upland agriculture development in

Yunnan, China and GMS

1400 General discussion and formulation of

some details of future PHT R&D works

Antonion Acedo Jr / Chair

Win Win Kyi / Rapporteur


1530 Coffee break

1600 Closing program

27 October 2007 (Saturday) Study tour to vegetable production, processing

and marketing firms


Participants Cambodia Borarin Buntong Lecturer/Laboratory Supervisor, Faculty of Agro-industry Royal University of Agriculture Phnom Penh, Cambodia Tel: +855 12 822 910 E-mail: [email protected]

China

Li YunShou Deputy Director and Associate Professor Agricultural Environment and Resources Research Institute Yunnan Academy of Agricultural Sciences (YAAS) Tao Yuan Village, LongTou Street, Kunming 650205, Yunnan, China Tel: +886 871 589 2205 Fax: +886 871 589 2112 Mobile: +886 1318 742 4343, 715 8905 E-mail: [email protected] Chen ZongQi Associate Professor, Agricultural Environment and Resources Research Institute Yunnan Academy of Agricultural Sciences (YAAS) Tao Yuan Village, LongTou Street, Kunming 650205, Yunnan, China Tel: +886 871 589 2205 Fax: +886 871 589 2112 Mobile: +886 1318 785 1558 E-mail: [email protected] Li Hong Deputy Director and Associate Professor, Administration Department of Science and Technology Industry, Yunnan Academy of Agricultural Sciences (YAAS) Deputy General Manager, Yunnan Agricultural Science and Technology Industry Management Co., Ltd. 761 Bai Yun Road, Jiangan District, Kunming 650231, Yunnan, China Tel: +886 871 513 6613 Fax: +886 871 589 2112 Mobile: +886 1388 803 0892 Email: [email protected]


Lao PDR Thongsavath Chanthasombath National Coordinator, ADB RETA 6376/ 6208 Project Deputy Director, Crop Multiplication Center (CMC) Department of Agriculture (DOA), Ministry of Agriculture and Forestry (MAF) P.O. Box 811, Vientiane Capital, Lao PDR Tel : +856 21 78 0040 to 41 Fax: +856 21 78 0042 Mobile: +856 20 2400224 E-mail: [email protected] Chansamone Phomachan Project Assistant, ADB RETA 6376/ 6208 Projects Crop Multiplication Center (CMC), Department of Agriculture (DOA) Ministry of Agriculture and Forestry (MAF) P.O. Box 811, Vientiane Capital, Lao PDR Tel : +856 21 78 0040 to 41 Fax: +856 21 78 0042 Mobile: +856 20 589 7188

Myanmar

Kyaw Nyein Aye Associate Professor, Yangon Technological University No. 503, Building A, Parami Condo Parami Road, Hlaing Township Yangon, Myanmar Tel: +95 (0) 9500802 Email: [email protected]

Philippines

Lemuel M. Diamante Invited Expert, Department of Food Science and Technology College of Engineering and Agri-industries Visayas State University Visca, Baybay, Leyte 6521, Philippines Tel: +63 53 335 2601 Fax: +63 53 335 2752 E-mail: [email protected]


Thailand

Sirichai Kanlayanarat Head, Division of Postharvest Technology King Mongkut’s University of Technology Thonburi Thungkru, Bangkok 10140, Thailand Tel: +66 2 4707720 Fax: +66 2 452 3750 E-mail: [email protected] Varit Srilaong Lecturer, Division of Postharvest Technology King Mongkut’s University of Technology Thonburi Thungkru, Bangkok 10140, Thailand Tel: +66 2 470 7726 Fax: +66 2 452 3750 E-mail: [email protected] Sasitorn Tongchitpakdee Invited Expert , Department of Food Science and Technology Faculty of Agro-Industry Kasetsart University 50 Phaholyothin Rd., Chatuchak Bangkok 10900, Thailand Tel: +66 2 562 5037 Fax: +66 2 562 5021 Mobile: +66 81 987 9204 Email: [email protected] Vietnam Chu Doan Thanh National Coordinator, RETA 6376/ 6208 Project Head, Department of Postharvest Technology Research Institute of Fruits and Vegetables (RIFAV) Trau Qui, Gia Lam, Hanoi, Vietnam. Tel: +84 4 876 5627 Fax: +84 4 827 6148 Mobile: +84 (0) 912 187 834 E-mail: [email protected]

[email protected] [email protected]

Luong Thi Song Van Researcher, Department of Postharvest Technology Research Institute of Fruits and Vegetables (RIFAV)


Trau Qui, Gia Lam, Hanoi, Vietnam Tel: +84 4 876 5627 Fax: +84 4 827 6148 Mobile: +84 (0) 914 240 281 E-mail: [email protected]

AVRDC

Antonio L. Acedo Jr. Regional Project Coordinator AVRDC-ADB Postharvest Projects (RETA 6208/6376) c/o AVRDC-ADB Postharvest Project Office

Crop Multiplication Center (CMC) Department of Agriculture (DOA) Ministry of Agriculture and Forestry (MAF)

PO Box 3938, Vientiane, Lao PDR Tel: +856 21 780028 Fax: +856 21 780042 Mobile: +856 20 288 3275 Email: [email protected]

Win Win Kyi Small-scale Enterprise Advisor AVRDC-ADB RETA 6208 Project c/o AVRDC-ADB Postharvest Project Office

Crop Multiplication Center (CMC) Department of Agriculture (DOA) Ministry of Agriculture and Forestry (MAF)

PO Box 3938, Vientiane, Lao PDR Tel: +856 21 780028 Fax: +856 21 780042 Mobile: +856 20 246 7713 Email: [email protected] Observers Nguyen Thi Hanh Researcher, Department of Postharvest Technology Research Institute of Fruits and Vegetables (RIFAV) Trau Qui, Gia Lam, Hanoi, Vietnam. Tel: +84 4 876 5627 Fax: +84 4 827 6148 E-mail: [email protected] Nguyen Thi Thuy Linh Researcher, Department of Postharvest Technology Research Institute of Fruits and Vegetables (RIFAV)


Trau Qui, Gia Lam, Hanoi, Vietnam Tel: +84 4 876 5627 Fax: +84 4 827 6148 E-mail: [email protected] Other Participants

Mr. Nguyen Dinh Hung Deputy Head, Department of Science and International Cooperation Research Institute of Fruits and Vegetables (RIFAV) Trau Qui, Gia Lam, Hanoi, Vietnam. Tel: +84 4 876 5627 Fax: +84 4 827 6148 Mr. Nguyen Khac Trung Researcher, Department of Postharvest Technology Research Institute of Fruits and Vegetables (RIFAV) Trau Qui, Gia Lam, Hanoi, Vietnam. Tel: +84 4 876 5627 Fax: +84 4 827 6148 Mr. Nguyen Duc Hanh, Vietnam Researcher, Department of Postharvest Technology Research Institute of Fruits and Vegetables (RIFAV) Trau Qui, Gia Lam, Hanoi, Vietnam. Tel: +84 4 876 5627 Fax: +84 4 827 6148 Mr. Tran Duy Long, Vietnam Researcher, Department of Postharvest Technology Research Institute of Fruits and Vegetables (RIFAV) Trau Qui, Gia Lam, Hanoi, Vietnam. Tel: +84 4 876 5627 Fax: +84 4 827 6148


www.avrdc.orgAVRDC – The World Vegetable CenterHeadquartersPO Box 42Shanhua, Tainan 74119Taiwan

T +886 (0) 6 583-7801F +886 (0) 6 583-0009E [email protected]

best practices in postharvest management of leafy

Documents