storing cut flowers
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Flower preservationTRANSCRIPT
Proper Temperatures for Storing Cut Flowers
By Brenda Ingram-Christian, eHow Contributor
Rapid cooling and proper temperature are key to maintaining the vitality of newly cut
flowers. Most cut flowers prefer temperatures at 32 to 33.8 degrees Fahrenheit,
according to ba.ars.usda.gov, with a relative humidity of 95 to 99 percent.
Pre-Cooling
• Flowers have high respiration rates which can cause them to dry out quickly. Getting your
harvested flowers from field to storage as quickly as possible is key to their survival and
longevity. Flowers that are packed quickly for shipment should be cooled prior to placing
them in boxes or they should be placed in boxes with vents to allow cool air to reach them.
Tropical Flowers
• Tropical flowers can be sensitive to cold storage and should be stored at 50 degrees
Fahrenheit. If they become too chilled, you may notice leaf or petal darkening or drying out.
Anthurium, bird of paradise, ginger, some orchids and a variety of foliage plants are sensitive
to colder temperatures, according to ba.ars.usda.gov.
Bulb Flowers
• Tulips, narcissus and hyacinths store best at 33 to 35 degrees Fahrenheit with a relative
humidity of 90 percent or more, according to University of Massachusetts Amherst. They
have a relatively short shelf life of three to seven days, dependent on the care that is given
post harvest. Gladiolas can be stored dry for up to a week or stored in a floral preservative
for up to two weeks at 36 to 40 F, according to Kansas State University.
Roses
• Roses need to be stored at 33 to 35 degrees Fahrenheit or the blooms may not open, or they
may experience a short vase life.
Considerations
• Never store fruit in the same cooler with fresh cut flowers. Fruit, especially apples, produces
ethylene gas which will cause cut flowers to age faster.
What is the floral fridge temperature for flowers?
Written by cassie damewood
Florists rely on the quality and freshness of their flowers to build and maintain a loyal clientele. To
ensure their supplies of cut flowers last as long as possible, their coolers and refrigerators must
consistently be kept at precise temperatures.
Keeping flowers at the right temperature preserves their beauty.
Jupiterimages/BananaStock/Getty Images
Refrigerator Temperatures
A floral cooler or refrigerator's ideal temperature is between 1.11 and 2.22 degrees Celsius for cut
flowers in a hydrating solution, although many units hover at around 38F. Temperatures that
fluctuate 5 degrees plus or minus of 38F can destroy or shorten the lives of flowers. If the flowers
have been removed from the hydrating mixture and placed in a preservative emulsion, they store
best at a constant 34F.
Display Units
Fresh flowers in a display unit also keep best between 34 and 36 degrees Fahrenheit to prevent
drooping or lost blooms. The containers should be plastic as metal may alter the pH balance of the
water or alter the preservative qualities of additives.
Humidity Requirements
Besides controlled temperatures, the humidity of floral storage areas must be carefully controlled.
Storage and display units need humidity levels of 90 to 95 per cent. Flowers placed in preservatives
require a minimum humidity level of 80 per cent.
Flowering Potted Plants
• Bulbs as flowering potted plants—keys to increased longevity (1.99MB pdf)
• Commercial transport of flowering potted plants: keeping quality beyond the bench (30.45MB pdf)
• Deliver poinsettias the consumer will enjoy. (1.16MB pdf)
• Effect of Nitrogen and Sulfur Applications on Post Chrysanthemum Production and Postharvest
Performance. II Plant Growth Responses (24.68MB pdf)
• Effects of exogenous sucrose on carbohydrate levels, flower respiration and longevity of potted
miniature rose (Rosa hybrida) flowers during postproduction (7.33MB pdf)
• Effects of Production and Postproduction Factors on Longevity and Quality of Kalanchoe (3.47MB
pdf)
• Growing Longer Lasting Bedding Plants (6.22MB pdf)
• High Production Temperature Increases Postproduction Flower Longevity and Reduces Bud Drop of
Potted, Miniature Roses 'Meriutral' and 'Medianclar' (623KB pdf)
• How to Make Long-Lasting, Top Performers out of Your Pot mums (11.44MB pdf)
• Post-greenhouse longevity of rooting room bulbs as flowering potted plants (15MB pdf)
• Postproduction performance of potted rose under simulated transport and low irradiance levels
(2.50MB pdf)
• Information about cut flowers
http://hort.ufl.edu/flowerpostharvest/potted-pubs.shtml
Cut Flowers
• Español
• AFE Special Report: Identifying Long-Lasting Cut Carnation Varieties (38KB pdf)
• AFE Special Report: Identifying Long-Lasting Cut Rose Varieties (65KB pdf)
• AFE Special Report: Improving Postharvest Performance of Alstroemeria (114KB pdf)
• AFE Special Report: Preventing Ethylene Injury to Fresh Cut Flowers (42KB pdf)
• AFE Special Report: Preventing Leaf Yellowing of Cut Oriental Hybrid Lilies (48KB pdf)
• AFE Special Report: Storage Temperature Effects on Cut Rose Varieties (58KB pdf)
• AFE Special Report: Three C's of Success with Fresh Cut Flowers - Care
• AFE Special Report: Three C's of Success with Fresh Cut Flowers - Cleanliness
• AFE Special Report: Three C's of Success with Fresh Cut Flowers - Cooling
• Bacteria-Free "Solutions" (703KB pdf)
• Can't Take the Heat (2.96MB pdf)
• Chill Out! (666KB pdf)
• Cleanliness Counts (584KB pdf)
• Cut Flowers: Handle with Care - Delivering Quality Flowers in a Global Marketplace (2.63MB pdf)
• De-myth-tifying Cut Flower Care (1.67MB pdf)
• Ethylene Happens (1.57MB pdf)
• Ethylene Protection (2.38MB pdf)
• Freshness Test: Will Your Flowers Pass? (2.03MB pdf)
• Gas Poisoning (1.85MB pdf)
• Give a Little Floral TLC (2.20MB pdf)
• Good Cents Marketing (640KB pdf)
• Good Intentions (5.28MB pdf)
• How's the Water? (1.59MB pdf)
• In Search of Freshness (507KB pdf)
• Long Live the Flowers: How to Keep your Flowers Going and Going (2.22MB pdf)
• Make Your Roses Last (1.31MB pdf)
• Problem Flowers: Tips for Solving the Common Longevity Challenges of 10 Problem Botanicals
(1.82MB pdf)
• Rose Care 101 (601KB pdf)
• Summer Smarts (2.44MB pdf)
• The Big Chill (1.62MB pdf)
• The Flower "Care-athon" (1.22MB pdf)
• The Secret of Longer-lasting Flowers (1.06MB pdf)
• Think Spring! Bulb Flowers are Favorites in Spring, But Need a Little Extra Care (1.09MB pdf)
• Thirst Aid (2.25MB pdf)
• Drenched for Success (678KB pdf)
• Effects of retail hydration on water uptake and quality of "Madame DelBard" roses after long-term
transport (2.45MB pdf)
• Plotted flowering plant publications
http://hort.ufl.edu/flowerpostharvest/cut-pubs.shtml
In What Temperature Should Fresh Flowers Be?
By Jacob J. Wright, eHow Contributor
A bouquet of fresh cut flowers usually brings a smile to someone's face. Since these
flowers lost their natural water source once severed from the plant, clean and fresh
water maintains their beauty. Temperature also plays a central role in the longevity of
cut flowers. Cooler temperatures slow bud opening or decay of stem and petal tissues.
Too warm temperatures hasten flower decay and increase the need for stems to absorb
adequate water.
Transportation to Market
• Do not refrigerate tropical cut flowers or foliage stems.
Whether grown thousands of miles away or a few feet from your front door, fresh cut flowers
begin to deteriorate once cut from the mother plant. Harvest of flowers often occurs in cool,
morning temperatures when plant tissues are turgid with liquid. Buds are tightly closed in
anticipation of later opening. During long-distance transport, refrigeration between 33 and 40
degrees Fahrenheit prolongs shelf life of temperate-climate cut flowers like tulips, roses, lilies,
pussy willows, camellias and lilacs. Tropical flowers, such as heliconias, gardenias and
gingers, suffer at temperatures below 55 F, so slightly warmer reduced temperatures are
needed during transport.
Room Temperatures
• Lilacs last longer in cooler, spring-like conditions.
Once on display, cooler temperatures slow the opening and duration of petals in individual
flowers. Interior spaces between 65 and 72 F supply cool temperatures to prolong fresh cut
flower vase life. Avoid placing cut flowers in direct sunlight where infrared radiation heats up
flower petal tissues and increase their need to absorb water to remain firm and fresh looking.
Tropical flowers suffer when exposed to chilly drafts near exterior windows and doors.
Water Temperatures
• Roses appreciate cool water for longer vase life.
Cut flower stems need to be initially placed in clean, fresh water at 110 F, according to the
University of Minnesota Extension. The very warm water facilitates rapid movement of water
molecules upward into the flower stems and is referred to as hardening. Keep the flower
stems in the water and allow the water to cool naturally to room temperature. Temperate-
zone flowers appreciate a cooler water temperature alongside cooler room temperatures.
Tropical flowers need at least room temperature water or slightly warmer around 75 F, since
their plant tissues don't normally receive chilly water in their growing environments.
Longevity Tips
• If the cut flower species is naturally from a cool habitat or flowers in a cool season, keep
room and water temperatures as cool as you can to prolong the flower display. Avoid
refrigeration and chilly water conditions for flowers that come from plants native to tropical
regions. The use of commercial floral preservatives is better than homemade remedies,
according to Mary H. Meyer of the University of Minnesota Extension.
What Is the Floral Fridge Temperature for Flowers?
By Cassie Damewood, eHow Contributor
Florists rely on the quality and freshness of their flowers to build and maintain a loyal
clientele. To ensure their supplies of cut flowers last as long as possible, their coolers and
refrigerators must consistently be kept at precise temperatures.
Refrigerator Temperatures
• A floral cooler or refrigerator's ideal temperature is between 34 and 36 degrees Fahrenheit
for cut flowers in a hydrating solution, although many units hover at around 38 F.
Temperatures that fluctuate 5 degrees plus or minus of 38 F can destroy or shorten the lives
of flowers. If the flowers have been removed from the hydrating mixture and placed in a
preservative emulsion, they store best at a constant 34 F.
Display Units
• Fresh flowers in a display unit also keep best between 34 and 36 degrees Fahrenheit to
prevent drooping or lost blooms. The containers should be plastic as metal may alter the pH
balance of the water or alter the preservative qualities of additives.
•
Humidity Requirements
• Besides controlled temperatures, the humidity of floral storage areas must be carefully
controlled. Storage and display units need humidity levels of 90 to 95 percent. Flowers placed
in preservatives require a minimum humidity level of 80 percent.
How to Store Flowers in the Refrigerator
By Cameron Easey, eHow Contributor
How to Store Flowers in the Refrigerator(Photo: Jeffrey Chen/Demand Media)
Flowers or flower arrangements that are received as a gift or for a special occasion can be kept for
long periods if they are properly stored. The key to storing flowers is to slow down the flowers
development and water loss. One way to do this is by putting the flowers or arrangement in your
refrigerator. Just make sure that there is enough room.
(Photo: Jeffrey Chen/Demand Media)
Fill the flower vase about three-quarters full with water.
(Photo: Jeffrey Chen/Demand Media)
Place the flowers that you want to keep in the vase.
(Photo: Jeffrey Chen/Demand Media)
Check the temperature of your refrigerator and make sure that it is set at or below 40 degrees.
(Photo: Jeffrey Chen/Demand Media)
Clear an area in your refrigerator to set the vase of flowers. Make sure to remove any fruit because
they should not be stored with the flowers.
(Photo: Jeffrey Chen/Demand Media)
Place the vase with the flowers on a shelf in the refrigerator.
Keep the flowers in the refrigerator for at least six hours each night. This will allow enough time for
the flowers to absorb the water and will stay fresh longer.
Optimal Temperature for Storing Flowers
By Fiona Wood, eHow Contributor
Cut flowers need to be well-hydrated to last. They should be kept in a cool place, but the
water in their vase right after they are cut should be warm.
Right after Cutting
• Flowers absorb warm water better than they absorb cool water. To ensure maximum
hydration, place them in a vase filled with water that is about 110 degrees Fahrenheit, about
the temperature of bath water. Then place them somewhere cool for an hour or two.
Storage Temperature
• Storing flowers at about 35 degrees Fahrenheit will keep them fresh longest. Cool
temperatures minimize water loss and slow development. Any temperature above freezing
but below 40 or 50 degrees Fahrenheit will work well. If the flowers are being displayed in a
room warmer than that, putting them in the fridge or another cool place at night or whenever
they are not being displayed will prolong their vase life.
Other Considerations
• Storing flowers in a fridge full of fresh produce may decrease their vase life, as fruits and
vegetables release ethylene, a ripening hormone that speeds aging in flowers.
How Long Can Fresh Flowers Live Without Water?
By Sarah Polson, eHow Contributor
Fresh flower arrangements are often used to mark a special occasion, brighten
someone's day or to just brighten up a room. How long those flowers will last depends on
the type of flowers as well as on what you do to take care of them.
Longevity by Type
• The first factor to consider in determining how long fresh flower arrangements will last is the
type of flowers in the arrangement. According to Teleflora, some of the longest-lasting cut
flowers are carnations, mini carnations, Anthurium and Star of Bethlehem. These variations
can last 14 days or more.
Examples of how long other flower types will last are as follows:
7-14 days: aster, chrysanthemum, gladiolus, heather, Asiatic and Oriental lilies, tuberose,
wax flower
5-7 days: anemone, calla, delphinium, freesia, gerbera, rose, snapdragon, zinnia
3-5 days: cornflower, daffodil, iris, lilac, lily of the valley, peony, tulip
1-2 days: gardenia
When to Cut
• If you are cutting the fresh flowers yourself to create an arrangement, when you cut them
can make a difference in how long they will last. The best time to cut flowers from your
garden is in the morning or late evening hours when it is cooler. Flowers are also most
fragrant in the mornings and filled with stored food.
Maturity
• The stage of maturity a flower is in can affect how long it will last after being cut. It's best to
cut flowers such as roses, daffodils, irises and gladiolas when they are still in the bud stage.
The flowers will then open and mature while in your flower arrangement.
Flowers such as marigolds and delphiniums, on the other hand, should be fully open before
they are cut.
How to Cut
• Use a sharp, unserrated knife or a pair of gardening shears, cutting the stems at a slant, and
immediately place the stems in warm water. If you bought precut flowers, you'll still want to
recut the stems when you get them home to give them a fresh surface with which to draw in
water. For best results, cut the stems under water to keep them from forming air bubbles
that prevent the stems from drawing in water.
• You'll also need to cut off any excess foliage on the stem that will be submerged in the water.
This will prevent them from molding in the water and creating bacteria that will shorten the
life of your blooms.
Water
• Most flowers need to be in warm water to help them live longer. Flowers produced by bulbs,
such as tulips and daffodils, need cold water.
Change the water every couple of days. Completely empty out the vase and replace the
water in it for your flowers. This is also a good opportunity to cut another 2 centimeters off
the stems to give them a fresh surface to draw water.
Flower Food
• Most fresh-cut flowers from the store will come with a packet of floral preservatives. The
preservatives contain sugar to help feed the flower, an acid compound to help the water
move more easily up the stem of the flower, and a biocide to help kill bacteria in the water.
You can make your own floral preservative. One simple solution is 2 ounces of Listerine
mouthwash per gallon of water. Listerine has sugar plus bacteria-fighting elements and is
acidic. You can also use lemon-lime soda in the water, plus a little bleach to help kill bacteria.
Tips
• Keep fresh flowers out of direct sunlight. It's also best to keep them away from vents,
radiators, drafts and TV sets so they stay cool.
In the evenings, move the flowers to a cooler place or refrigerate them to help them last
longer.
Keep flowers away from fruit. Fruit gives off a chemical that will age flowers more quickly.
The differences between a floral cooler & a beverage cooler
Written by tatyana ivanov
Commercial coolers are used for a variety of different purposes, and to cool many different products.
Two common types of coolers are the floral cooler and the beverage cooler. Both of these types of
coolers can be seen in supermarkets and floral shops, and many also exist in back rooms for storage.
Floral and beverage coolers are used for different purposes, and so they have different cooling
systems.
Florists use coolers to keep their flowers fresh
Jupiterimages/liquidlibrary/Getty Images
Purpose
One of the main differences between a floral cooler and a beverage cooler is their purpose. Florists do
not use coolers to make their flowers cold, but rather because the cool air prevents the flowers from
wilting and keeps them fresh. Supermarkets and other stores use beverage coolers to provide a cold
product to consumers. Because of these different objectives, both types of coolers have different
cooling mechanisms and options to accommodate different products.
Cooling Mechanisms
Beverage coolers and floral coolers use cold air in different ways. Floral coolers use a regulated air
system that prevents the flowers from being damaged by the influx of air, while preventing them
from drying out. Similarly, floral coolers allow you to adjust the humidity to be between 80 to 95 per
cent inside the cooler, which also helps prevent drying. Beverage coolers are designed to keep
beverages as cool as possible without freezing, and generally try to keep the humidity as low as
possible. Additionally, floral cooler thermostats are usually set lower than beverage cooler
thermostats.
Types of Coolers
Floral and beverage coolers come in a variety of models with different features. Both types of coolers
are made in walk-in and reach-in styles. The walk-in models are much larger and are meant to be
used more for storage than for product display. The reach-in coolers come with different door
options, including a sliding door and a door that you pull open. Either type of cooler can be custom
made to accommodate a specific space. Beverage coolers, however, come in an additional model that
is not available in floral coolers; the commercial beer cooler opens from a sliding door on the top.
Considerations
Though there are several companies that can convert a beverage cooler into a floral cooler, these
conversions can be more costly than purchasing a cooler than has been manufactured for flowers.
Determine how much stock you will be storing in your beverage or floral cooler before purchasing it,
so that you know what size cooler to get. Additionally, both floral and beverage coolers come with
different shelving options. Beverage coolers generally have more shelves placed closer together to
accommodate as much product as possible, while floral coolers have more spacious shelves to
prevent damage to the flowers.
Commercial Cooling of Fruits, Vegetables, and Flowers
Publication Number: 21567
Author: JAMES THOMPSON
Inventory Type: Paperback
Language: English
ISBN-13: 978-1-60107-619-9
Copyright Date: Rev. 2008
Length: 61 pp.
Challenges in Postharvest Handling of Cool Season Vegetables
Marita Cantwell
(Dept. Plant Sciences, University of California, Davis, CA 95616,Tel: 530-752-7305;email:
[email protected]; Webpage: http://postharvest.ucdavis.edu)
Abstract:This paper is an overview of important postharvest challenges facing handlers and
marketers of cool season vegetable crops from a California perspective. Consumers are increasingly
concerned about microbial food safety. Recent outbreaks of food pathogens on leafy greens and
other vegetables have focused much attention on food safety. The implementation of GAPs (good
agricultural practices) and GMPs (good manufacturing practices) is necessary to ensure safe products.
Many buyers require third party certification of compliance with good practices. There is increased
focus on temperature management and strengthening weak links in the cold chain. The most
effective way to ensure the quality and safety of vegetables is to maintain the cold chain after initial
cooling and provide as close to optimum storage/transport temperatures as possible. Other
environmental conditions that can significantly impact product shelf-life and quality include relative
humidity, presence of ethylene gas, and the composition of the atmosphere. Increased use of
modified atmospheres is another important trend in postharvest handling of vegetable products.
Atmospheres may be provided in consumer packages, in pallets shrouds, in storage rooms, or in
marine containers. The main benefits of modified atmospheres are to reduce rates of ripening and
senescence, to slow softening, to reduce decay, and possibly to reduce compatibility problems in
mixed load shipments. Ethylene contamination and its control remains another challenge. Molecular
modification of ethylene synthesis and perception sites in products, and the use of chemical blockers
of ethylene receptors are two strategies to reduce undesirable ethylene effects. In current
commercial handling, however, low temperature, ventilation and ethylene oxidation are the most
common practices to reduce ethylene concentrations. The increasing sophistication of packaging
materials, sanitation procedures, and emphasis on low temperature processing and handling have all
contributed to the success of fresh-cut products in the market place. Cool season fresh-cut vegetables
constitute the major volume of these products. Consumers want products with better sensory quality.
Although the diversity of products and presentations has increased, increased efficiency and
traceability during distribution are increasingly required by supermarket chains and food service
distributors.
Key words: Cool season vegetables; Postharvest handling ; Challenges
Introduction
In the U.S. fresh fruit and vegetable marketing system the focus is on adding value and
decreasing costs by streamlining distribution and understanding customer needs. This U.S. produce
marketing system has evolved toward increased direct sales from shippers to final buyers.
Consumers place high value on taste/flavor, freshness, and appearance of vegetables. Product form
and packaging are changing as more companies introduce value-added products like fresh-cut
produce, designed to respond to the growing demand for convenience in food preparation and
consumption. Fresh produce continues to be a critical element in the competitive strategy of retailers,
and year-round availability is now a necessity for both food service and retail. Key drivers in produce
marketing are global retail players, global retail brands, growing role of private labels, retailer-supplier
contracts/partnerships and the decline of the spot market.
Some of the challenges in postharvest handling of cool season vegetables to be briefly discussed
include ① increased concern over microbial food safety, ②better cold chain management of
perishables, ③role of modified atmospheres and ethylene, ④fresh-cut and value-added
products,⑤traceable and efficient handling during distribution.
1....Microbial Food Safety Considerations
Ensuring microbial food safety is the single most important challenge confronting the fresh
produce industry today, especially for cool season leafy vegetables that are eaten uncooked. Control
of decay causing fungal and bacterial microorganisms has been the main focus in the past, but
control of human pathogens (viral, parasitic and bacterial) now grabs the spotlight. Leafy vegetables
are produced in the “natural” environment, and therefore should be expected to carry a wide variety
of microorganisms. Most microorganisms on fresh produce are harmless, and the number of
organisms itself is not an indication of quality. Total counts of bacteria on freshly harvested
vegetables can vary from ten to millions of cells per gram of product, depending on environmental
factors. More important to food safety is the assurance that specific human pathogenic organisms
are not present. Concerns about the microbial food safety of fresh produce have been increasing
among consumers. One of many such efforts around the nation, a Center for Produce Safety was
founded in 2007 at UC Davis to serve as a clearinghouse for research and training on fresh produce
safety (http://cps.ucdavis.edu/).
The main strategy to ensure microbial food safety is to prevent contamination. In 1998 the FDA (US
Food and Drug Administration) issued a guidance document for the fresh produce industry (Table 1).
The goals of these guidelines are to reduce microbial risks by preventing contamination and by
improving the effectiveness of control measures when contamination exists. More recent documents
have been developed to add practical checklists to these general guidelines, such as the USDA Good
Agricultural Practices and Good Handling Practices Audit Verification Checklist
(http://www.fsis.usda.gov/). Other industry-government efforts have led to the development of
commodity specific guidelines (http://www.unitedfresh.org/newsviews/guidance_documents). After a
major food safety incident on spinach, leafy green vegetable growers in California developed a
marketing agreement which specifies metrics and verification processes to ensure microbial food
safety http://www.caleafygreens.ca.gov/ and this is now being proposed as the basis of a national
program (http://www.nlgma.org/).
An example of changing postharvest practices is the use of water. Water in dump tanks, water
flumes and recycled cooling operations is particularly susceptible to cross-contamination by decay-
causing organisms and/or microorganisms that cause food borne illness. Some of the organisms of
current concern include bacteria (E. coli strains, Salmonella spp., Listeria monocytogenes), protozoan
parasites (Cryptosporidium spp., Cyclospora spp.) and viruses (Hepatitis A, Norwalk virus). The main
purpose of sanitizers in water used in postharvest handling operations is to reduce microbial
contamination of the water and prevent cross contamination. Disinfectants do not eliminate
organisms from fresh produce. Typically, chlorinated wash water reduces microbial populations of
fresh fruits and vegetables by less than 100-fold. Most of the water sanitation in California is based
on the use of chlorinated disinfectants. Other alternatives are being actively evaluated including
ozone, chlorine dioxide, acidified sodium chlorite, ionization, UV and other types of irradiation,
hydrogen peroxide, and peroxyacetic acid.
Table 1....Brief summary of the main principles described in the FDA guide to minimize microbial food
safety hazards for fresh fruits and vegetables and elaborated on in subsequent guidelines
Postharvest step Principle emphasized
General Prevention of microbial contamination of fresh produce is favored over reliance
on corrective actions once contamination has occurred. Accountability at all
levels of the agricultural and packing operations is important to a successful food
safety program
Water Wherever water comes into contact with fresh produce, its quality dictates the
potential for pathogen contamination.
Manure & biosolids Properly treated manure or biosolids can be an effective and safe fertilizer.
Animal feces While not possible to exclude all animal life from fresh produce production areas,
many field programs include elements to protect crops from animal damage.
Worker health,
hygiene
Infected employees who work with fresh produce increase the risk of
transmitting food- borne illness.
Field sanitation Fresh produce may become contaminated during pre-harvest and harvest
activities from contact with soil, fertilizers, water, workers, and harvesting
equipment.
Packing facility Maintain packing facilities in good condition to reduce the potential for microbial
contamination.
Transportation Proper transport of fresh produce will help reduce the potential for
contamination.
Traceback The ability to identify the source of a product can serve as an important
complement to
good agricultural and management practices.
Verification Once good agricultural and management practices are in place, ensure that the
process
is working correctly.
2. Strengthening weak links in the cold chain
The most effective way to maintain the quality and safety of fresh fruits and vegetables is to
maintain the cold chain and provide as close to optimum storage temperatures as possible. Table 2
summarizes the cold chain for fresh fruits and vegetables and requirements for successful movement
from field to fork. Cool the product as soon as possible after harvest. Temperature is the most
important factor determining deterioration rate. Decreasing the temperature reduces the product’s
metabolism (respiration and ethylene production), water loss, and the growth of decay-causing fungi
and bacteria. Mechanical refrigeration is the basis for most cooling methods. Room cooling (placing
products in a refrigerated room) is a relatively low cost, but also slow method. The cold air needs to
circulate around the product to remove heat, so leave space between boxes and between pallets.
Forced-air cooling pulls the cold air through the containers and greatly increases the rate of cooling.
A cold room can be modified with portable and fixed forced-air handlers to increase cooling rates.
Hydrocooling (by submersion or spraying cold water) products that tolerate wetting provides fast
cooling and avoids water loss. It takes more time to hydrocool packed product and wood or waxed
containers are needed. Sanitation of the hydrocooling water (usually by chlorination) is critical to
prevent contamination. Some products tolerate contact with ice; crushed or flaked ice can be applied
directly or as slurry in water. Evaporative cooling can be used in hot dry environments by pulling
outside air through wet pads to provide high humidity, cooler air. Other environmental conditions
affect shelf-life (relative humidity, ethylene, and atmosphere composition), but these factors are less
important than temperature control and all are influenced by storage temperature.
Freshness is a very important quality attribute. Freshness can be maintained by expedited
marketing, but can also be achieved by storing for short periods (days) under the proper conditions.
The longer the period from harvest to consumption, the greater the emphasis on good temperature
management. The importance of temperature and prompt cooling are clearly shown in the case of
broccoli shelf-life (Figure 1). If products are stored for long periods (weeks), they need to be kept
very close to their ideal storage conditions to minimize quality loss. Once the product has been
cooled, low rates of air circulation reduce water loss during storage. Cool season vegetables require
high humidity during storage to prevent dehydration. All cool season vegetables (Brassicas, lettuces,
celery, carrots, etc) are non-chilling sensitive products with recommended storage temperatures of 0-
3°C). Chilling-sensitive vegetables (recommended temperatures vary from 7-13°C) include basil,
cucumbers, eggplants, tomatoes, peppers. A listing of specific temperature and storage
recommendations for many fruits and vegetables can be found at
http://postharvest.ucdavis.edu/Produce/Storage/index.shtml. Postharvest treatments and
technologies other than temperature management (plastic packaging, humidity control, ethylene
control, modified atmospheres, decay-control treatments) are considered supplemental to this
fundamental technology. Although marketing requirements are changing for fresh produce, the
implementation of basic postharvest principles remains relevant to all fresh produce (Table 3).
Figure 1. Impact of temperature (left) and cooling delays (right) on shelf-life of broccoli
Table 2. Maintaining the cold chain for perishable fruits and vegetables
Postharvest operation Temperature Requirements
Harvest Protect the product from the sun
Transport quickly to the packinghouse
Cooling Minimize delays before cooling
Cool the product thoroughly as soon as possible
Temporary storage Store the product at optimum temperature
Practice first-in first-out rotation
Ship to market as soon as possible
Transport to market/distributor Use refrigerated loading area
Cool truck before loading
Load pallets towards the center of the truck
Put insulating strips inside door or reefer if truck makes multiple stops
Avoid delays during transport
Monitor product temperature during transport
Handling at distribution Use a refrigerated unloading area
Measure product temperature
More product quickly to the proper storage area
Transport to retail or foodservice operations in refrigerated trucks
Display at proper temperature range
Handling at home or Store product at proper temperature
Foodservice outlet Use the product as soon as possible
Table 3....Ten important guidelines for postharvest handling of cool season vegetables
1. MATURITY. Harvest the product at the correct stage of maturity.
2. REDUCE INJURIES. Reduce the physical handling to a minimum; every time product is handled,
it is damaged.
3. PROTECT PRODUCT. Protect the harvested product from the sun; bring it rapidly from the
field/exposed area to the packing station and keep out of the direct sun. Transport carefully
4. CLEANLINESS & SANITATION. Keep the packing line as simple as possible and keep it clean.
If water is used, use clean water or a sanitizer if the water is reused. Maintain strict worker
hygiene. Comply with guidelines for GAPs (Good Agricultural Practices) and GHPs (Good Handling
Practices).
5. PACK CAREFULLY. Sort, classify and pack the product carefully to achieve uniformity and to prevent
damage (compression, scrapes, etc.) which causes decay and inferior quality; use an adequate box or
container. Packaging can also be informative.
6. PALLETIZE. Insure that the boxes are well aligned on the pallet and that the pallet is strapped.
7. COOL. Cool the product as soon as possible after harvest; generally for every hour of delay from
harvest to initiate cooling, one day of shelf-life is lost. Lowering product temperature is the most important
way to reduce deterioration.
8. KNOW PRODUCT. Know the requirements of the market (size, maturity, etc) and the product
handling requirements (temp., RH, shelf-life, etc.) of the product.
9. COORDINATION. Always try to coordinate the postharvest handling so that it is efficient and rapid.
Postharvest handling maintains the quality of a product, it can not improve it.
10. TRAINING and COMPENSATION. Train and compensate well the workers involved in critical
postharvest handling steps; make sure that workers have the necessary tools to facilitate their
work
3. Modified atmospheres and ethylene
Modification of the atmosphere typically involves lowering the oxygen and raising the carbon
dioxide concentrations in the atmosphere surrounding a product. Normal air is comprised of about
78% nitrogen, 21% oxygen, 0.03% carbon dioxide and other inert gases. Sometimes removal of
ethylene is also considered in modified atmospheres. The term controlled atmosphere is used when
the atmosphere can be monitored and controlled, and the term modified atmosphere is used when
the atmosphere is different from normal air but there is no ability to control concentrations. The
latter includes the use of pallet shrouds with high carbon dioxide for decay control and plastic film
packaging for fresh-cut vegetables. Controlled and modified atmospheres are a supplement to
proper temperature and relative humidity and may offer several benefits: retard color and texture
changes, retard senescence and compositional changes in vegetables, reduce physiological disorders
such as chilling injury, retard decay growth, and control insects in stored products. Products differ in
their tolerance to low oxygen and high carbon dioxide atmosphere medication and Table 4 provides
some examples. If atmospheres are outside these beneficial levels, products can be damaged. Most
of the information on CA/MA has been developed empirically. There is a need to better understand
the physiological effects of short-term and long-term CA. In the future, ‘sense and respond’
technologies may permit a more a tailored use of MA.
Table 4....Examples of the tolerance of vegetables to low oxygen and high carbon dioxide levels
Minimum oxygen concentration tolerated Maximum carbon dioxide concentration tolerated
% O2 Products % CO2 Products
0.5 salad-cut vegetables 2 tomato, pepper, lettuce, endive, Chinese
cabbage, celery, artichoke, sweetpotato
1.0 mushroom, garlic, onion, most
fresh-cut fruits and vegetables
5 peas, chile peppers, eggplant, cauliflower,
cabbage, radish, carrot
2.0 sweet corn, beans, celery, lettuce,
cabbage, cauliflower
10 cucumber, summer squash, snap bean,
okra, asparagus, broccoli, parsley, leek,
green onion, bulb onion, garlic, potato
3.0 broccoli, tomato, pepper,
cucumber, artichoke
15 sweet corn, mushroom, spinach, kale,
Swiss chard
5.0 green peas, asparagus, potato
Ethylene is a potent gaseous plant growth regulator that may affect many aspects of plant growth
and development. It is produced by all fruits and vegetables, and may have both beneficial and
detrimental impacts on fresh produce (Table 5). In climacteric fruits, ripening is regulated by ethylene
(bananas, avocado, mango, papaya, apple, tomato, etc) but ethylene has no or minimal affect on the
ripening process of non-climacteric fruits (strawberry, citrus, pepper). However for most leafy and root
vegetables, ethylene production rates are very low and these vegetables are damaged by ethylene in the
storage environment. There are 5 strategies to control ethylene: avoid, remove, inhibit production,
inhibit action, and modify plant response through genetics. Avoidance includes keeping ethylene
generating fruits away from sensitive vegetables, and keeping extraneous sources of ethylene such as
propane forklifts away from sensitive products. Removal techniques include ventilation with fresh air,
absorption of ethylene (with carbon filters for example), and oxidation of ethylene (permanganate and UV
scrubbers for example). Low temperature retards ethylene production by fruit and there are specific
inhibitors for enzymes of the ethylene biosynthesis pathway. Inhibition of ethylene action can be
achieved with low temperature, controlled atmospheres, and use of chemical inhibitors. Finally, genetic
or molecular engineering of specific enzymes has been very effective to control ethylene production and
ethylene action and this is used commercially in some flowers. Currently the most important of the
chemical inhibitors of ethylene action is 1-MCP (1-methylcyclopropane as it binds to the ethylene
receptors on cell membranes, rendering the product insensitive to ethylene.
Table 5....Examples of consequences of ethylene action in fruits and vegetables
Beneficial effects Detrimental effects
1. Stimulates ripening of climacteric fruit 1. Accelerates senescence
2. Promotes color development in fruits 2. Causes excessive softening in some fruits
3. Promotes de-greening of citrus 3. Stimulates chlorophyll loss, yellowing
4. Stimulates dehiscence in nuts 4. Stimulates sprouting
5. Alters sex expression in Cucurbits 5. Promotes discoloration reactions and related disorders
6. Promotes flowering in pineapple 6. Promotes abscission of leaves and flowers
4. Increased Diversity of Value-added Products
The average number of items handled in a U.S. fresh produce department is over 300 today, up
from fewer than 140 twenty years ago. Yet six commodity groups still make up 42 percent of total
sales, just as they did in the 1980s: bananas, apples, citrus fruits, potatoes, lettuce, and tomatoes.
Part of the diversity in the U.S. supermarket is the result of diversity within basic produce categories,
as illustrated with lettuce: intact crisphead and loose leaf lettuces are packed into various size carton
and plastic boxes; lettuces are commonly marketed as cut salad products in different sizes for retail
and food service. Also there may be special types of the conventional items. Broccoli, for example,
has many “relatives” including gailan, rapini, purple broccoli, broccoflower, broccoli romanesco.
Diversity of produce is also seen currently in the offerings of products according to production
systems; conventional, organic, sustainable, or protected cultivation.
Fresh-cut or minimally processed or fresh-cut products have grown rapidly during the past few
years, extending from the foodservice sector to the retail shelf. Fresh-cut produce now represents
about 15% of the value (12-15 billion dollars) of fresh produce in U.S. supermarkets. Packaged salads
alone are valued at about 50% the total value of fresh-cut produce items. Fresh-cut products are
prepared and handled to maintain their fresh state while providing convenience to the user.
Producing minimally processed products involves cleaning, washing, trimming, coring, slicing,
shredding, and other related operations. There are many examples of fresh-cut products among the
vegetables: fresh salad mixes, cut green beans, broccoli and cauliflower florets, slaw mixes of
cabbage and carrots, celery and carrot sticks, sliced mushrooms, whole peeled and diced onions,
garlic, and potatoes. About 70% of the total volume of fresh-cut items is comprised of lettuce, green
cabbage, carrots, onions, potatoes, broccoli and cauliflower. These are typically expected to have a
shelf-life of 10-14 days. The other fresh-cut vegetables usually have less shelf-life (Cantwell, 2009).
The increasing sophistication of packaging materials, strict sanitation and concerns about microbial
contamination, and emphasis on low temperature processing and handling have all contributed to the
success of fresh-cut products in the market place (Table 6).
Throughout the 1990s a major industry debate existed over whether it was preferable to process
at the shipping point, where product freshness is at its maximum level, or at the destination, where
product reworking can occur. Both require optimal temperature management throughout distribution
to maximize marketable product. It now appears evident that regional processing plants will
dominate, due to proximity to market and the demand for just-in-time deliveries. Although the fresh-
cut segment of the produce industry is relatively new, there has been an increase in industry
consolidation as this product category has matured. Currently, two California-based companies
control around 65 percent of total retail packaged salad sales. In some cases, California processors
have developed joint ventures with regional processors to expand distribution of their brands into
new geographic markets.
Table 6....Basic requirements for preparation of minimally processed fruits and vegetables
• High quality raw material: Variety selection; Production practices; Harvest and storage conditions
• Strict hygiene and good manufacturing practices: Use of HACCP principles; Sanitation of
processing line, product and workers
• Low temperatures during processing: Use of cold water flumes; Process room is refrigerated;
Process line shut down if product temperature exceeds 4°C
• Careful cleaning and/or washing before and after peeling: Good quality water (sensory, micro, pH)
• Use of mild processing aids in wash water for disinfection or prevention of browning and texture loss:
Chlorine, ozone, other disinfectants; antioxidant chemicals; calcium salts to reduce firmness loss.
• Minimize damage during peeling, cutting, slicing and/or shredding operations; Sharp knives on
cutters; elimination of defective and damaged pieces
• Removal of excess moisture: draining, spin or air drying; combination technologies
• Correct packaging materials and packaging methods: Selection of plastic films to ensure adequate
oxygen levels to avoid fermentation; selection of appropriate films for piece size and product type
• Correct temperature during distribution and handling: Keep all fresh-cut packaged products at 0-5°C
5. Packaging and traceable, efficient distribution
Although the diversity of products and presentations has increased, there is a trend to simplify
the excessive types of packaging in the U.S. In some distribution systems, plastic containers are
being used, but most vegetables are still marketed in carton boxes. Carton manufacturers have
developed a new carton with a common standard pallet ‘footprint’ of 16 x 24, but of varying heights
to accommodate a wide range of products, with interlocking tabs along the long side, and open retail
display-ready http://www.internationalpaper.com/PDF/PDFs_for_Packaging/CFSTechnicalManual.pdf.
Such a modular system for packing fresh produce was proposed many years ago by produce trade
associations working groups to reduce the plethora of packaging types used (>200). This packaging
is similar to the ‘Eurobox’ concept of interlocking, stacking, layered, standard modular corrugated
boxes designed specifically for produce. Supermarket chains are interested in reduced package types
to permit implementation of mechanized selection systems at their produce distribution centers.
Changes in plastic or carton containers dimensions and volumes may affect cooling rates and require
changes in vent placement, pallet stacking patterns and cooler design and management.
Successful produce marketing firms will become more market-driven, identifying and meeting the
specific needs of each market segment for quality, packaging, product form, merchandising and
information. More produce marketing firms are adopting a supply chain management approach,
emphasizing faster delivery, more accurate temperature management, and improved packaging
technologies, all based on better demand information. Broader adoption of standardized PLU (Product
Look Up) codes and the introduction of more packaged produce items will permit better information
management through EDI (Electronic data interchange) and category management. More recently
RFID (Radio frequency identification) technology allows for identification of a package from the field
through the entire marketing system and allows for complete traceability. However, there are some
technical challenges with RFID use on high water content perishable products and current costs for
implementation are considerable high. Other approaches include the Global Trade Item Number
(GTIN) for external traceability. http://www.unitedfresh.org/newsviews/produce_traceability_initiative
Specific information exists for postharvest handling requirements of many specific products.
Many produce handlers, however, do not have a good understanding of the interaction between the
handling steps or are unable to integrate the entire handling system to make management decisions.
Certainly, ensuring microbial food safety requires an integrated approach to the postharvest value
chain. Unnecessary delays are particularly troublesome for more perishable leafy greens and for
packaged fresh-cut products. An example of the increased need for integration and logistics of
perishable handling is emphasized by the World Food Logistics Organization (www.wflo.org), which
developed from the previous Refrigeration Research and Education Foundation. Their focus is on
perishable warehousing, transportation, distribution, information and logistics. “Food miles” is a
recent environmental issue that concerns the costs to transport fresh produce from source of
production to the consumer and is one reason for ‘buy local, buy fresh’ campaigns
(http://attra.ncat.org/farm_energy/food_miles.html). And more generally, concerns over sustainability
(environmental, social, and economic) have impacted all segments of the fresh produce industry.
References
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