testing ethylene control technologies in domestic fridges - wrap

Final report - Strategies to Reduce Waste of Fresh Produce

Testing ethylene control

technologies in domestic fridges

A report describing trials to assess the potential benefits of ethylene control technologies within domestic fridges, as a means of extending the shelf-life of fresh produce, and thereby reducing household food waste.

Project code: RBC820-002

Research date: March 2009 – June 2010 Date: May 2011

WRAP‟s vision is a world without waste, where resources are used sustainably. We work with businesses and individuals to help them reap the benefits of reducing waste, develop sustainable products and use resources in an efficient way. Find out more at www.wrap.org.uk

Written by: Dr. Debbie Rees (NRI, University of Greenwich), Dr. Neil Hipps (East Malling Research), Dr. Richard

Colgan (NRI, University of Greenwich), Karen Thurston (East Malling Research)

Legacy research commissioned by the previous government

Front cover photography: Fridge fruit (ID: 16639)

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Testing ethylene control technologies in domestic fridges 3

Executive summary

WRAP is working with industry to identify ways of reducing wastage of fresh fruit and vegetables through the

whole supply chain. From the packhouse, through distribution depots and retail outlets, to domestic households,

every step of the chain offers opportunities to realise the benefits of avoiding waste.

Research1 has found that the majority of food and drink waste occurs at the end of the chain – in the household.

This project focuses on the potential for ethylene control technologies to extend the shelf-life of fresh produce in

domestic fridges, thereby helping to reduce household food waste. Through practical experiment, it measured the

effects of three technologies on fresh produce stored in fridges, against „control‟ produce stored normally in

identical fridges. The tested technologies were:

Absorption of ethylene in the fridge by use of Extrafresh discs containing potassium permanganate.

Addition of ozone to the fridge to act as an ethylene control agent. Ozone also destroys and/or retards the

growth of bacteria and fungal spores.

Treatment of fresh produce with an ethylene inhibitor, 1-methylcycopropene, the active ingredient of

SmartfreshTM.

Ethylene is important because it can increase the rate of deterioration of fresh produce. The concentrations at

which ethylene can affect produce is very low, and therefore methods of reducing its presence, or equally its

effects, may be beneficial.

Previous research2 has suggested that consumers should be encouraged to store more fruit and vegetables in the

fridge at home to extend their shelf-life. One possible consequence of this may be an increase in ethylene

concentrations in domestic fridges. The widespread presence of more ethylene-generating produce may have

adverse consequences for the quality of ethylene-sensitive produce. This may then support a rationale for using

one of the three ethylene control technologies examined here.

Researchers developed a methodology to compare these technologies against an untreated control scenario. The

trial design allowed direct comparison between the technologies. Fresh produce was selected to ensure that the

following categories were included in each of the tests:

Produce shown to be „most wasted‟ in the household.

Produce which generates ethylene.

Produce which is sensitive to ethylene.

The amount of fresh produce was chosen to reflect a scenario of greater fridge storage of fruit and vegetables in

the home. A range of produce was chosen that offered a “worse case” scenario in terms of likely ethylene

concentrations in the fridges. The same combination of items was placed in each fridge. Ethylene levels were

then measured in the fridges at set intervals over a three-week period, and the on-going quality of the

refrigerated produce was monitored for deterioration using a visual scoring system.

The results showed that the action of opening and closing the fridge had a significant effect on reducing ethylene

concentrations. The absorption technology (a) was found to reduce ethylene concentrations, but its effect on

fresh produce quality, as against the control, was limited. The ozone technology (b) had little effect on either

ethylene or the fresh produce at the output, discharge interval and frequency settings selected. The ethylene

inhibitor technology (c) reduced ethylene concentrations, and lowered the rate of deterioration for a limited

selection of produce, but had no, or negligible effects on others.

During this study the fridges were set at 4°C as recommended by fridge manufacturers. Notably, under these

conditions all the fresh produce used in the tests had a shelf-life of seven or more days, and eight of the 21

product had a shelf-life greater than 21 days. This would suggest that if fridge temperatures are at the

recommended level, there may be no need for additional technologies to extend shelf-life. The report, therefore,

concludes that the use of ethylene control technologies at this stage of the supply chain is unlikely to have great

benefits, and should not be given high priority.

1 Waste arisings in the supply of food and drink to households in the UK, WRAP, 2009

2 Helping consumers reduce fruit and vegetable waste, WRAP, April 2008


Contents

1.0 Introduction and background to the project ............................................................................. 6 1.1 Overview of supply chain food waste .................................................................................... 6 1.2 Objectives .......................................................................................................................... 7 1.3 Technical background .......................................................................................................... 7

1.3.1 The role of ethylene in the deterioration of fruit and vegetables .................................. 7 1.3.2 The rationale for controlling ethylene within fridges ................................................... 9 1.3.3 Potential strategies for controlling ethylene and its effects within fridges. .................. 10

1.4 Project team ..................................................................................................................... 11 2.0 Methodology ............................................................................................................................. 12

2.1 Basis of the trials .............................................................................................................. 12 2.2 Choice of produce for fridge storage ................................................................................... 12 2.3 Effect of produce selection on ethylene levels and production rates within fridges ................... 14 2.4 Protocol for trials to test fridge technologies ........................................................................ 15

2.4.1 Fridge allocation ................................................................................................... 15 2.4.2 Packaging and positioning of produce within the fridges ........................................... 16 2.4.3 Door opening ....................................................................................................... 18

2.5 Application of ethylene control technologies......................................................................... 18 2.5.1 Ethylene removal using ExtraFresh discs ................................................................. 18 2.5.2 Ozone as an ethylene control agent ........................................................................ 18 2.5.3 Inhibition of ethylene action using Smartfresh™ 1-MCP ............................................ 19

2.6 Ethylene measurements ..................................................................................................... 19 2.7 Duration of trials ............................................................................................................... 19 2.8 Quality assessment of produce during trials ......................................................................... 19 2.9 Creation of a visual score system ........................................................................................ 19 2.10 Standardisation of fridge temperatures................................................................................ 20

3.0 Results ...................................................................................................................................... 22 3.1 Ethylene production rates and sensitivities of products ......................................................... 22 3.2 Assessing the effect of Extrafresh discs ............................................................................... 22

3.2.1 The effect of Extrafresh discs on measured ethylene concentrations .......................... 22 3.2.2 The effect of Extrafresh discs on product quality ...................................................... 23

3.3 Assessing the effect of ozone treatment .............................................................................. 27 3.3.1 The effect of ozone treatment on measured ethylene levels ...................................... 27 3.3.2 The effect of the ozone generator on product quality ............................................... 27

3.4 Assessing the effect of SmartfreshTM treatment .................................................................... 31 3.4.1 The effect of SmartfreshTM treatment on measured ethylene concentrations ............... 31 3.4.2 The effect of SmartfreshTM treatment on product quality .......................................... 32

4.0 Summary and discussion of findings ........................................................................................ 37 4.1 Fridge temperatures and normal shelf-life of produce ........................................................... 37 4.2 Ethylene levels in fridges ................................................................................................... 37 4.3 The effect of tested technologies on ethylene levels ............................................................. 38 4.4 The effect of tested technologies on product quality for specific products ............................... 38

4.4.1 Broccoli ................................................................................................................ 39 4.4.2 Cucumber ............................................................................................................ 40 4.4.3 Green pepper ....................................................................................................... 40 4.4.4 Nectarine ............................................................................................................. 41

5.0 Conclusions ............................................................................................................................... 42 5.1 Shelf-life of fresh produce under refrigeration without ethylene control technologies ............... 42 5.2 Extrafresh discs ................................................................................................................. 42 5.3 Ozone generation .............................................................................................................. 42 5.4 SmartfreshTM .................................................................................................................... 42 5.5 The potential benefits of complete ethylene removal ............................................................ 42 5.6 Recommendations ............................................................................................................. 42

Appendix 1 Visual scoring system ........................................................................................................ 43


Glossary and acronyms 1-methylcyclopropene (1-MCP): a chemical that inhibits ethylene action in plant tissues, widely used in the UK to treat apples after harvest to extend storage life. It has no known toxic effects. Avoidable food waste: food and drink thrown away that was edible at some point before disposal (e.g. slice of bread, apples, meat). Climacteric fruit: fruit which have a pattern of ripening that is stimulated by ethylene, involves synthesis of more ethylene and cannot be stopped once started. Large changes occur in colour, texture and taste during ripening and there is a burst in respiration rate to provide the energy for this. Examples include apples and bananas. Ethylene gas (C2H4): produced by most plant tissues and acts a plant hormone, stimulating a range of plant responses including fruit ripening and tissue senescence.

Ethylene scrubbing: ethylene removal. Extrafresh disc: a product that absorbs ethylene, using potassium permanganate impregnated on clay granules. Flame Ionisation Detector (FID): detects chemicals on the basis of their ionisation in a flame. Fungistatic: fungal growth inhibitor. Lloyd penetrometer: a machine that measures hardness of fresh produce. Microbial contamination: contamination with fungi and/or bacteria. Mycotoxin: a chemical produced by fungi that is toxic to humans. Non-climacteric plant tissues: those that are sensitive to ethylene but do not respond by synthesising more ethylene. Typical responses include loss of green colour in non-climacteric fruit, such as oranges, and senescence, such as in broccoli. Ozone generator: a producer of ozone. Ozone is primarily used in the fresh produce industry to control microbial contamination. Ozone also reacts with and destroys ethylene. Packhouse: a facility where fresh produce is graded for quality and packed. Parts per million (ppm): a measure of concentration equivalent to 0.0001%. Parts per billion (ppb): a measure of concentration equivalent to 0.0000001%.

Senescence: death of plant tissues in a controlled process. Examples include shrivelling and drop of flower petals, browning and drop of leaves in autumn. SmartfreshTM: the commercial form of 1-methylcyclopropene.


1.0 Introduction and background to the project

1.1 Overview of supply chain food waste

One of WRAP‟s key priorities is the reduction of food waste across the supply chain3. The overall level of food

waste from the grocery sector is estimated to be at least 11 million tonnes (Table 1), and much of this goes to

landfill4. The majority of food and drink waste occurs at the household level (8.3 million tonnes). WRAP is

carrying out a number of activities to reduce household food waste as part of the “Love Food Hate Waste‟

programme5 and Courtauld Commitment6, a voluntary agreement aimed at improving resource efficiency and

reducing the carbon and wider environmental impact of the grocery retail sector.

Table 1 Estimated total food and drink waste arisings from the supply of food and drink to households in the UK

Supply chain stage

Total waste arisings

Million tonnes

Manufacture 3.2

Distribution and retail 0.37

Household 8.3

Total 11.87

Source: “Waste arisings in the supply of food and drink to households in the UK” WRAP, 2009

As well as decreasing the amount of material being sent to landfill, the reduction of food waste is key to reducing

greenhouse gas emissions. Food 20307 reports that “the greenhouse gas footprint of the UK food chain was 160

million tonnes CO2 equivalent in 2006, an estimated 22% of emissions associated with all UK economic activity”.

A WWF report8, states that a further 101 million tonnes CO2 equivalent from land use change in other countries is

attributable to UK food. This results in the food chain contribution to UK CO2 equivalent emissions rising to 30%.

Figure 1 indicates that of all household food and drink waste (8.3 million tonnes) 36% is fresh vegetables, salads

and fruit (equating to 3 million tonnes)9.

Figure 1 Proportion of weight of all food and drink waste, split by food group

3 http://www.wrap.org.uk/wrap_corporate/about_wrap/food_waste_one_of.html

4 Waste arisings in the supply of food and drink to households in the UK, WRAP, 2009

5 www.lovefoodhatewaste.com

6 http://www.wrap.org.uk/retail/courtauld_commitment/index.html

7 http://www.defra.gov.uk/foodfarm/food/pdf/food2030strategy.pdf

8 How low can we go? WWF, January 2010: http://assets.wwf.org.uk/downloads/how_low_can_we_go.pdf

9 Household food and drink waste in the UK, WRAP, 2009


Food and drink waste has been categorised by how avoidable the waste is:

Avoidable – food and drink thrown away that was, at some point prior to disposal, edible (e.g. slice of bread,

apples, meat). Possibly avoidable – food and drink that some people eat and others do not (e.g. bread crusts), or that can be

eaten when a food is prepared in one way but not in another (e.g. potato skins).

Unavoidable – waste arising from food or drink preparation that is not, and has not been, edible under normal circumstances (e.g. meat bones, egg shells, pineapple skin, tea bags).

Of the 3 million tonnes of fresh vegetables salads and fruits, 1.36 million tonnes is considered to be avoidable. It

is this avoidable waste that is being targeted within this project.

Reducing this waste not only has a direct effect by reducing landfill and greenhouse gas emissions, but will also

reduce the level of resources that were used unnecessarily to create and dispose of the food and drink that is

produced, but not consumed. These resources include land and water for agriculture, inorganic fertilisers,

transport fuel, packaging materials, and electricity for storage at low temperature.

1.2 Objectives

WRAP has been working to identify approaches to reducing wastage of fresh fruit and vegetables through the

whole supply chain, from packhouse, through distribution depots and retail outlets to domestic households,

concentrating on the impact of ethylene and microbial contamination. This project concentrates on methods of

reducing wastage within the household, with the following objective:

To assess the impact of ethylene removal and an ethylene action inhibitor on waste reduction of

fruits and vegetables in domestic fridges.

A previous WRAP project10 recommended that retailers should improve storage information given to consumers,

and encourage the storage of more fruit and vegetables in the fridge at home, thereby extending shelf-life and

reducing domestic waste. One expected consequence of storing more fruit in this way might be an increase in

ethylene concentrations within fridges. It is therefore important to assess the potential impact on shelf-life of any

enhanced ethylene levels and strategies to mitigate this.

1.3 Technical background

1.3.1 The role of ethylene in the deterioration of fruit and vegetables

Ethylene (C2H4) is produced naturally by most plant tissues, especially ripening fruit. It is a plant hormone that

controls many biological processes. Among plant hormones, ethylene is unusual because it is a gas. The

implication of this is that if one plant or plant organ starts to produce ethylene, nearby plant tissues are also

affected. For plants, many processes involving tissue death, such as leaf drop in deciduous trees, petal drop in

flowers, over-ripening of fruit, are actively controlled as part of the natural life cycle. Many of these are

controlled / stimulated by ethylene. For this reason ethylene can speed up deterioration in fruits and many

vegetables, particularly leafy greens.

As it controls so many processes associated with the quality of fruit and vegetables, ethylene is an extremely

important chemical for the fresh produce handling industry. On the one hand it is used to trigger ripening in

fruits. Thus bananas are transported green to the UK and are then stimulated to ripen by being fumigated with

ethylene within warm ripening rooms. On the other hand, as ethylene will stimulate deterioration and senescence

(an active process of cell death that leads to tissue deterioration), it is important to control concentrations in

order to maintain quality. Thus, there is a growing recognition of the importance of controlling ethylene in fresh

produce store rooms, and therefore an increase in the use of ethylene scrubbers.

The concentrations at which ethylene can affect produce are very low. There is evidence that many products are

sensitive to concentrations well below 100 parts per billion (ppb). Ethylene is known to build up in packhouses to

concentrations near 1,000 ppb (= 1 part per million (ppm)), which is above the threshold of sensitivity of most



produce. A study conducted on a range of produce showed a 60% extension of post-harvest life when stored in

<5 ppb compared with 100 ppb ethylene11.

The biochemistry of how ethylene controls plant processes is very complex and beyond the scope of this report.

However, in order to relate the observation of ethylene levels to their likely effects on fresh produce, it is useful

to understand some of the background principles.

Processes controlled by ethylene can be classified into two types:

System 1. Ethylene „stimulates‟ the process. If ethylene concentrations are increased the process goes faster,

and if ethylene concentrations are reduced or ethylene is removed completely then the process slows/stops. This system applies to ethylene stimulation of the deterioration/senescence of vegetables, over-ripening/senescence of

fruit, discolouration of cucumber and browning of broccoli.

System 2. Ethylene acts as a switch that cannot be stopped. Thus ethylene triggers the biological process. If

ethylene levels are reduced or ethylene is removed completely then the process continues, albeit at a slower

pace. This is the case for the initiation of ripening of certain fruits, which are called climacteric fruit. These include bananas, apples, tomatoes, kiwifruit, pears and avocadoes, but not grapes, oranges and lemons.

On the whole, during handling of the produce in the grocery supply chain, ripening would already have been

initiated in all climacteric fruits that were used in this project. Therefore, we are concerned with System 1

processes and the exposure to continuous ethylene. Short-term exposure would not have dramatic effects.

Figures 2–4 demonstrate some of the effects of exposure to ethylene.

Figure 2 Ethylene treatment triggers the ripening of bananas which are climacteric fruit and therefore need only

temporary exposure (System 2)

11 Wills, R.B.H., Ku, V.W., Shohet, D. and Kim, G.H. (1999) Importance of low ethylene levels to delay senescence of non-climacteric fruit and vegetables. Australian Journal Of Experimental Agriculture, 39 (2), 221-224


Figure 3 Exposure to ethylene can induce colour loss of cucumbers. This is a natural “ripening” process, but

detrimental to quality

Figure 4 Exposure to ethylene can induce brown streaks in leafy vegetables, as shown in this example of

Chinese leaves

1.3.2 The rationale for controlling ethylene within fridges

Following the previous WRAP project12, exploratory trials suggested that the presence of fruit in fridges may have

slight negative effects on the visual quality of certain vegetables. These effects may result from heightened levels

of ethylene generated by the fruit (unpublished data).

The trials undertaken for the previous project found that, generally, vegetable quality related to ethylene

concentrations within the fridges, once they had accumulated to levels above thresholds reported to cause

adverse effects on quality. However, despite high ethylene concentrations accumulating within the trial fridges

over three to four days, vegetable quality was generally good for seven days, regardless of whether they were

stored with or without fruit.

The trials therefore suggested that the presence of ethylene-generating produce in refrigerators might have

adverse consequences on the quality of ethylene-sensitive produce. Over a 14-day period, the highest recorded

ethylene concentrations in fridges containing only vegetables were 31 and 66 ppb. This compares with maximum

concentrations of 1677 and 9915 ppb where apples and pears were included.



It was noted that opening the fridge doors to inspect produce flushed out much of the ethylene from the fridges.

The fridge with the highest ethylene concentration lost 96% and 90% of its ethylene, when the door was opened

on days four and eight respectively. Residual ethylene levels measured after closing the fridge doors were similar

irrespective of the concentration at the time of opening. However, residual concentrations were above the 100

ppb concentration often cited as the threshold level that enhances senescence in vegetables.

The vegetables affected by heightened levels of ethylene were lettuces, broccoli, cauliflowers and Brussels

sprouts. Cabbage appeared not to be affected. Those that were affected by ethylene showed symptoms regarded

as typical of accelerated senescence, such as yellowing and leaf detachment (cauliflowers). With the exception of

Brussels sprouts, and to a lesser extent broccoli, the adverse effects of ethylene were nevertheless slight.

Other studies have shown that ethylene levels in fridges were about 10-fold higher where apples were included,

and were likely to result in a 30% reduction in post-harvest life of a range of products13. As expected, the quality

of most types of vegetables is better under lower ethylene conditions, but even a level of 70 ppb (recorded in the

study above) is higher than the threshold level for the physiological effects of ethylene indicated in some

studies14. It is, therefore, important to establish the benefits of the removal of ethylene from fridges, or the

inhibition of its effects, especially for ethylene sensitive products that are known to contribute significantly to

levels of domestic waste.

1.3.3 Potential strategies for controlling ethylene and its effects within fridges.

For this project, three strategies were tested within domestic fridges: ethylene removal by absorption; the use of

ozone which destroys ethylene; and, inhibition of ethylene action. Each of these strategies is described below,

while the specific technologies employed are described in section 2.

Ethylene removal

A number of technologies already exist for the removal of ethylene from the storage atmosphere; these include

the use of potassium permanganate that absorbs ethylene, and the use of catalytic scrubbers that catalyse the

breakdown of the chemical. Absorbing the gas with potassium permanganate is the cheapest of these, and

therefore the one most likely to be appropriate for use in domestic fridges. Extrafresh discs15 used in the project

are an example of this technology.

Ozone as an antimicrobial and ethylene control agent

Ozone reacts with and destroys ethylene, and therefore has potential as an ethylene removal agent16. It also has

several other characteristics that make it attractive for maintaining quality of fresh produce: it destroys and/or

retards the growth of bacteria and fungal spores (depending on concentration); controls odours; improves

firmness in some fruits; has been reported to induce resistance to postharvest decay development and increase

the levels of antioxidants in the fruit; and can degrade pesticides and mycotoxins.

In the mid 1990s, ozone was approved for food processing in Australia, France and Japan, and it has been

granted the status of Generally Recognized as Safe (GRAS) by the FDA (Food and Drug Administration) in the

USA. The use of ozone in organic products is also approved in the USA. Its use is free of residues, because the

only product of ozone when it decomposes is oxygen and its half-life is only about 12 hours at room temperature.

UAP ozone generators (provided by Onnic Ltd17) were used in this study to generate ozone.

Inhibition of ethylene action

An alternative to removing ethylene from the fridge environment is to de-sensitise fresh produce to the

deleterious effects of ethylene. The ethylene inhibitor 1-methylcyclopropene (1-MCP), the active ingredient of

„SmartFresh‟TM18 (Rohm and Haas Company, USA), is widely used to treat apples prior to storage in order to

13 Wills, R.B.H., Ku, V.W., Shohet, D. and Kim, G.H. (1999) Importance of low ethylene levels to delay senescence of non-climacteric fruit and vegetables. Australian Journal Of Experimental Agriculture, 39 (2), 221-224

14 Wills, R.B.H., Warton, M.A. and Ku, V.V.V. (2000). Ethylene levels associated with fruit and vegetables during marketing. Australian Journal of Experimental Agriculture, 40, 465-70

15 http://extrafresh.com.au/welcome.php 16 Skog, L. J. and Chu, C. L. 2001. Effect of ozone on qualities of fruits and vegetables in cold storage. Can. J. Plant Sci. 81: 773-778.

17 http://www.onnic.co.uk/home.htm

18 http://www.smartfresh.com/smartfresh.html


maintain quality, particularly during post-storage shelf-life19. Treatment with 1-MCP also slows the ripening of

many other climacteric fruits such as plums and tomatoes. Although „SmartFreshTM‟ technology is not currently

available at the domestic level, there is an opportunity for product development if the application of 1-MCP

proved effective in enhancing the quality and extending the life of fresh produce stored in fridges. There is a

need to evaluate the potential benefits of this technology for the most wasted types of fruits and vegetables.

1.4 Project team

East Malling Research Neil Hipps Project Manager

Karen Thurston Postharvest technologist

David Johnson Postharvest technologist

Natural Resources Institute Debbie Rees Postharvest technologist

Richard Colgan Postharvest technologist

Mack Multiples Cristian Metzger Innovation technologist

Bruce McGlashan Fresh produce technologist

Sainsburys Theresa Huxley Fresh produce technologist

Onnic International Peter Holmes Ozone technology

MAPCAP Technology Nigel Parker Ozone technology

ICA David Bishop Extrafresh discs technology

Stephen Lawrence Extrafresh discs technology

Landseer Ltd Mark Tully Smartfresh Technology

19 Johnson, D.S. (2008). Factors affecting the efficacy of 1-MCP applied to retard apple ripening. Acta Horticulturae, 796, 59-67


2.0 Methodology

2.1 Basis of the trials

Three technologies were tested:

1 Extrafresh discs containing potassium permanganate to absorb ethylene (provided through ICA Ltd).

2 UAP ozone generators (provided by Onnic Ltd) to break down ethylene.

3 Smartfresh 1-MCP (provided by Landseer Ltd) to inhibit ethylene action.

Details of the number and location of devices is given below.

The trials were designed with the premise that the most relevant information could be obtained if fresh produce

was assessed under the conditions that it would actually experience in the home. Trials were therefore carried

out using the fridge compartments of a set of „Beko‟ 300L domestic fridge-freezers. This particular make of fridge

is frequently used in the UK, and is similar to many other commonly purchased models. Eight fridges were used

simultaneously. In order to conduct trials with sufficient replication, each strategy was tested against untreated

controls in separate trials.

The produce included within each fridge was chosen to be typical of what may be found within a family fridge. A

range of packaging was included, with consideration of what was most likely to be found in a domestic fridge. For

the same reason some products (e.g. melons, cucumbers) were cut into two pieces, as this would have a

significant effect on ethylene production rates.

The effect of the technologies on produce quality was followed for three weeks, as it was considered unlikely that

consumers would knowingly keep produce for longer than this. Quality of produce was assessed using a visual

scoring system, which was developed specifically for this project.

2.2 Choice of produce for fridge storage

When choosing the range and quantity of produce to be stored in the fridges during the trials, there were two

main considerations:

(a) which ethylene-generating produce to place in the fridge environment; and

(b) which ethylene-responsive produce to place in the fridge environment.

For (a), tests were conducted to determine the effects of produce on ethylene levels, and these are discussed in

section 2.3.

It was decided that (b) should comprise produce that contributes most significantly to levels of waste in domestic

households. The selection of produce was, therefore, made using data available at the start of the project on

those that are “most wasted” in the household (WRAP diary research 2007; unpublished). Produce for which

refrigeration is not recommended were not included.

Subsequently, more up-to-date information was obtained by WRAP. The more recent data on the “most wasted”

fresh produce within the household is presented in Figures 5 and 620. The levels of waste have been separated

into avoidable, possibly avoidable and unavoidable. For the purposes of these trials, the avoidable waste is the

most important.

20 Household food and drink waste in the UK, WRAP, 2009


Figure 5 The weight of fruit waste within UK households, split by avoidability

tonnes per year

0 50,000 100,000 150,000 200,000 250,000 300,000 350,000

Banana

Apple

Orange

Melon

Stone fruit

Other citrus

Soft / berry fruit

All other fresh fruit

Avoidable Possibly avoidable Unavoidable

Source: Household Food and Drink Waste in the UK WRAP 2009

Figure 6 The amount of vegetable waste within UK households, split by avoidability

tonnes per year

0 200,000 400,000 600,000 800,000

Potato

Mixed vegetables

Onion

Carrot

Cabbage

Lettuce

Tomato

Other root vegetables

Cucumber

Sweetcorn / corn on the cob

Broccoli

Cauliflower

Leafy salad

Bean (all varieties)

Pepper

Leek

Mushroom

Spring onion

All other fresh vegetables and salads

Avoidable Possibly avoidable Unavoidable

Source: Household Food and Drink Waste in the UK WRAP 2009

Table 2 shows the selection of produce used in these trials, compared with the produce more recently identified

with high levels of avoidable waste. These columns correspond well, with only a few variations. The produce that

might have been included, had this data been available at the time of trial planning, are sweetcorn, green beans

and leeks. In the case of stone fruit, nectarines were included as an example, but other examples such as plums

or mangoes might also have been included.


Table 2 Commodities included in the main trials to assess ethylene control technologies, compared to

commodities most recently identified with high avoidable waste

Commodities included in trials

(* indicates items previously identified as most

wasted21)

Commodities with high levels of avoidable

waste22 for which refrigeration is

recommended

*Apple (Braeburn and Granny Smith) Apple

Asparagus

Avocado

*Broccoli Broccoli

*Pear

*Cabbage

*Cauliflower Cauliflower

*Carrot Carrot

Celery

*Cucumber Cucumber

*Grape

*Green pepper Pepper

*Honeydew Melon Melon

*Kiwifruit

*Lemon Other citrus

*Lettuce Lettuce

*Mushroom Mushroom

Nectarine Stone fruit

*Satsuma Orange

Strawberry Soft berry fruit

*Tomato Tomato

Other leafy salad

Sweetcorn

Beans

Leek

Shaded products have significant “avoidable” waste, but were not included in the main trials.

2.3 Effect of produce selection on ethylene levels and production rates within fridges

At present there is no information on the actual concentrations of ethylene in domestic fridges in the UK, and it

was considered beyond the scope of this project to undertake the size of study that would be necessary to obtain

reliable data. Ethylene concentration is likely to be affected by the range of fresh produce stored in the fridge and

the frequency of door opening.

Two selections of produce (Table 3) were tested for their effects on ethylene levels within the fridges. Figure 7

indicates the ethylene levels measured within fridges with these two selections. For selection A, ethylene

concentrations were below 500 ppb, whereas for selection B the ethylene concentrations ranged between 1,500

and 3,500 ppb. Higher levels for selection B were expected due to the greater number of apples and pears and

the inclusion of a cut melon. The main trials of this project were conducted using selection B, in order to

determine produce shelf-life and the effects of ethylene control technologies in the presence of high ethylene

producers.

21 WRAP diary research 2007, unpublished

22 As identified in “Household Food and Drink Waste in the UK” WRAP, 2009


Table 3 The selection of produce to include within each fridge was very important. Two sets of produce were

assessed for their effects on the ethylene levels within the fridges

Produce selection A Produce selection B

4 Apples 4 Braeburn and 4 Granny Smith apples

Asparagus Asparagus

Avocado 2 Avocadoes

Broccoli Broccoli

- Cabbage

Carrots Carrots

Cauliflower Cauliflower

Celery Celery

Cherries -

Cucumber ½ Cucumber

Grapes Grapes

Green pepper 2 Green peppers

- 6 Kiwifruit

- Lemon

Lettuce Lettuce

- Melon cut into two

- Mushroom

Nectarines 4 Nectarines

- 4 Pears

Raspberries -

- Satsuma

Figure 7 Ethylene concentrations measured within fridges in which produce selection A or B had been stored.

Each data point relates to the mean of values measured over three weeks for an individual fridge

0

500

1000

1500

2000

2500

3000

3500

4000

0 1 2 3 4 5 6

Me

an

eth

yle

ne

le

ve

l in

fri

dg

e (

pp

b)

Produce selection A Produce selection B

2.4 Protocol for trials to test fridge technologies

2.4.1 Fridge allocation

The technologies were tested separately, so that within each trial there were two treatments: untreated control

vs. ethylene control technology. Four fridge-freezers were assigned to each treatment. The allocation of the

fridges was made randomly for each trial.

Trials were carried out using the fridge compartments of a set of eight „Beko‟ 300L domestic fridge-freezers kept

in one room (in two rows on either side of the room) (Figure 8).


Figure 8 Four domestic fridge-freezers arranged on one side of the trial room

The fridge-freezers had an upper fridge and lower freezer. The fridge contained two crispers at the bottom. In

order to simulate the loading of domestic fridge freezers, the freezer compartments were filled with packages of

sliced bread, and in addition to the products being tested, the fridge compartment of each of the eight fridge-

freezers contained the following items, in addition to fresh fruit and vegetables:

UHT milk x1 carton

Tomato puree x1 tube

Sweet pickle x1 jar Jam x1 jar

Marmalade x1 jar

Olives x1 jar Lemon juice x1 bottle

Salad cream x1 bottle

Tomato ketchup x1 bottle Lard x1 pack

Butter x1 pack

Apple juice x2 bottle.

2.4.2 Packaging and positioning of produce within the fridges

The amount of each product, type of packaging and position of storage of the produce is summarised in Table 4

and illustrated in Figure 9. Where produce was „cut‟ this is also indicated. All produce was purchased from a local

Sainsbury‟s supermarket, and was placed in the fridges within two hours of purchase.

The importance of storing most „free-flow‟ products in plastic bags was demonstrated clearly in a previous WRAP

project23. It was, therefore, appropriate for most commodities to test the ethylene control technologies on

bagged products. However, we recognise that most consumers open bags as they use produce. For that reason

where bags were used the ends were kept open.

The „Beko‟ fridge-freezers used in this project have two separate crispers. Ethylene-sensitive produce (mainly

green vegetables) was stored in the crisper compartments and the ethylene-producing products (mainly

climacteric fruits) were stored on the shelves. In this way high ethylene producers and ethylene-sensitive

products were not stored together in close proximity.



Table 4 Commodities included in the trial, with packaging and location within the fridge

Product Amount Packaging Location in fridge

Apple 2 x 6 Open bags Shelf

Asparagus 1 pack Open bag Crisper

Avocado 2 Unbagged Shelf

Broccoli 1 head Open bag Crisper

Cabbage green 1 Open bag

Carrot 1x 500g pack Open bag Crisper

Cauliflower 1 head Open bag Crisper

Celery 1 Open bag Crisper

Cucumber 1 Sleeved, cut into two Crisper

Grapes 1 bag Open bag Shelf

Green pepper 2 Unbagged Crisper

Kiwifruit 4 Open bag Shelf

Lemons 2 Open bag Shelf

Lettuce 1 Open bag Crisper

Melon (Honeydew) 1 Cut into two halves Shelf

Mushroom 1 Paper bag Shelf

Nectarines 4 Open bag Shelf

Pears 6 Open bag Shelf

Satsumas 4 Open bag Shelf

Strawberries 1 punnet Plastic punnet Shelf

Tomato 6 Open bag Shelf

Figure 9 The arrangement of produce within each fridge during the main trials


2.4.3 Door opening

The fridge doors were opened for 30 seconds twice a day (early morning and late afternoon) to simulate

mealtime activity in the home. In surveys carried out by FRPERC24, 30 seconds was the maximum time that fridge

doors were left open.

The doors were kept sealed over the weekend period to determine ethylene build-up during a period of inactivity,

as would be the case where the householder(s) left the premises for a short vacation. It is presumed that in

preparation for longer vacations, perishable products would be removed from the fridge compartments.

2.5 Application of ethylene control technologies

2.5.1 Ethylene removal using ExtraFresh discs

Following discussions with the manufacturing company, six Extrafresh discs were placed in each fridge, one on

each of the four shelves and one in each crisper compartment.

Figure 10 Extrafresh disc

2.5.2 Ozone as an ethylene control agent

A single UAP ozone generator was used in each fridge. The generator was programmed to produce ozone for two

minutes during each 15-minute period. As ozone is heavier than air, the generators were placed on the top shelf

in order to optimise the distribution of ozone through the fridge.

Figure 11 Ozone generator

24 The Food Refrigeration and Process Engineering Research Centre (FRPERC) at the University of Bristol


2.5.3 Inhibition of ethylene action using Smartfresh™ 1-MCP

When water is mixed with Smartfresh™, 1-MCP is released as a volatile. At the start of each trial, products were

placed in sealable chambers (two fridges of produce per chamber) maintained at 20ºC, and exposed to volatile 1-

MCP at an initial estimated concentration of 625 ppb. All packaging was open to allow free circulation of the gas.

The chamber was kept closed for 24 hours after which produce was placed in fridges and the storage trial

initiated. Produce for the non-treated controls were kept in identical chambers under identical conditions for 24

hours.

2.6 Ethylene measurements

The fridge atmosphere was sampled before door opening on days of quality assessment. A pump was connected

to two tubes that penetrated the fridge door seal (top and bottom) and samples of the circulated atmosphere

were extracted by syringe from a septum port inserted into one of the gas lines. Ethylene concentration was

measured by gas chromatography, using a Flame Ionisation Detector (FID). This method of measurement is

accurate to 10 ppb and there is no interference from other volatile chemicals.

2.7 Duration of trials

Each trial ran for three weeks with produce quality being assessed twice a week and coincident with the early

morning door opening. Products remained in the fridge for the duration of the experiment.

2.8 Quality assessment of produce during trials

Quality assessment was carried out over time based on visual quality, using a visual score system created before

the trials were initiated (see section 2.9). For selected produce, internal assessments to check for physiological

disorders and/or texture measurements using a Lloyd penetrometer were made at the end of the storage period.

Produce was weighed at each assessment to check for weight loss.

2.9 Creation of a visual score system

Loss of visual quality is a major reason for consumers wasting fruits and vegetables. However, it is also likely that

consumers have differing views about what is and is not visually acceptable. In order to make the results of the

experiments as objective as possible, it was necessary to develop a scoring system for quality, so that any

benefits of ethylene control technologies could be quantified.

Small quantities of each of the products to be used in trials were purchased from a local Sainsbury‟s supermarket

and kept in air storage at 20oC to hasten deterioration. All products were weighed on a daily basis and a full

visual description of quality made. Symptoms associated with senescence of the products included yellowing,

softening, decay, abscission and browning. A photographic record was kept so that visual quality could be

matched with the descriptions and a scoring system developed. This process was continued for each product

until it deteriorated to an unacceptable level. A subjective assessment was made by the investigators of the point

at which each product became unacceptable for use. The resulting scoring system is given in Appendix 1.

As fresh produce deteriorated the score increased from 1 (good) to 5 (poor quality). Most produce had a five

point scale, although for some (e.g. strawberry, mushroom) it was possible to increase this to 6. For each type of

produce used in the main trials, the score that in the assessor‟s view reached the limit of acceptable quality was

recorded (Table 5). This was subsequently used to calculate any change in shelf-life period found as a result of

the technologies tested.

Table 5 The score considered to indicate the limit of acceptable quality for each product, using scores in

Appendix 1

Product Limit of good quality

Apple >2

Asparagus 3

Avocadoes 3

Broccoli 3

Cabbage 3


Carrot 2

Cauliflower 3

Celery 2

Cucumber 2

Grapes 2

Green pepper 3

Kiwifruit 3

Lemon 2

Lettuce 2

Melon 2

Mushroom 3

Nectarine 2

Pear 3

Satsuma >2

Strawberries 2

Tomatoes 2

NB. Apple and satsuma did not deteriorate beyond the limit of good quality during the whole assessment period.

2.10 Standardisation of fridge temperatures

Even though the fridges maintained constant temperatures when tested before the trial, in a preliminary trial it

was found that once loaded with produce, fridge temperature was unacceptably variable (varying within a two

degree range). To reduce variability during trials, the temperature of each fridge was checked twice weekly using

a glass thermometer inserted into a bottle of glycerol, and the fridge setting adjusted as necessary. Tables 6, 7

and 8 summarise the temperature data for the three trials reported.

Table 6 Extrafresh trial fridge temperatures

Fridge Treatment Mean Temp. °C

(main section)

Mean Temp. °C

(crisper)

Average manually

recorded temp °C

1 Extrafresh 3.8 2.5 3.7


3 Control 4.0 2.2 3.9

4 Control 4.1 2.5 4.0


6 Control 4.0 3.0 3.8


8 Control 3.5 2.9 3.7

Table 7 Ozone generator trial fridge temperatures


(main section)

Mean Temp. °C

(crisper)

Average manually

recorded temp °C

1 Control 3.9 2.5 4.0

2 Ozone generator 3.7 2.0 3.7

3 Control 4.0 2.1 3.9



6 Control 4.0 3.0 3.8


8 Control 3.3 2.9 3.9


Table 8 SmartfreshTM trial fridge temperatures


(main section)

Mean Temp. °C

(crisper)

Average manually

recorded temp °C

1 Control 3.7 2.6 3.6

2 Smartfresh 3.7 1.7 3.7

3 Control 4.1 2.3 4.1

4 Control 3.9 2.4 3.7



7 Control 3.2 2.3 3.7



3.0 Results

3.1 Ethylene production rates and sensitivities of products

In order to understand the results it is very useful to have information on the ethylene production rates and

sensitivity of the individual products included in the trials. Table 9 summarises the available information.

Table 9 Ethylene production and ethylene sensitivity of fruits and vegetables used in these trials. Figures based

on data from University of California (VH-very high, H-high, M-moderate, L-low, VL-very low)

Product Rate of production of ethylene Sensitivity to ethylene

Apple VH H

Asparagus VH H

Avocadoes

Broccoli

Cabbage VL H

Carrot VL H

Cauliflower VL H

Celery VL H

Cucumber VL M

Grapes L H

Green pepper VL L

Kiwifruit L H

Lemon

Lettuce VL H

Melon

Mushroom VL M

Nectarine

Pear H H

Pepper L L

Satsuma VL M

Strawberries L L

Tomatoes H L

3.2 Assessing the effect of Extrafresh discs

3.2.1 The effect of Extrafresh discs on measured ethylene concentrations

Figure 12 indicates that Extrafresh discs reduced the levels of ethylene within the fridges from a range of 1,000 –

4,000 ppb down to approximately 500 ppb. Each set of data refers to measurements from an individual fridge.

Measurements were made on Monday and Thursday mornings. Fridge doors were opened for 30 seconds on

Monday – Friday in the morning (after ethylene assessment) and in the late afternoon. Doors were not opened

during the weekend. The higher levels observed at day 7, 14 and 21 were measured on Monday morning after

the fridges had been closed since Friday afternoon, whereas the lower levels measured on days 3, 10 and 17

were measured on a Thursday morning at which point the fridges had been closed for one night only. The

difference in these levels indicates the significant effect that opening the fridge doors can have on ethylene

concentration.


Figure 12 Ethylene concentrations measured within fridges with or without Extrafresh discs

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 5 10 15 20 25

Storage time (Days)

Eth

yle

ne c

on

cen

trati

on

(p

pb

)

Control 1

Control 2

Control 3

Control 4

E/Fresh 1

E/Fresh 2

E/Fresh 3

E/Fresh 4

3.2.2 The effect of Extrafresh discs on product quality The quality of each product during the three week storage period is summarised in Figure 13. The main

observations are as follows:

In terms of visual quality score, Extrafresh significantly slowed the rate of deterioration for broccoli, and

cucumber (just statistically significant to 10%).

For apples, no visible deterioration was observed throughout the storage period.

There were some other commodities for which there appeared to be a trend for slower deterioration with

Extrafresh, (cauliflower, cabbage, tomato) and some for which the quality seemed worse with Extrafresh

(lemon, mushroom). However, as the results were not statistically significant, this could have been random

effects due to natural product variability.

Internal quality was assessed at the end of three weeks for avocado and nectarines, but no differences were

observed between treatments.

No differences in rates of weight loss were observed for any product (data not shown).

Figure 13 Quality scores for fresh produce stored in domestic fridges over three weeks, with (blue) and without

(grey) Extrafresh discs. Each data point is the mean of values assessed for produce in four replicate fridges

Apple- Braeburn

0.5

1.0

1.5

2.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1= b

est)

Control

Extrafresh

Apple- G Smith

0.5

1.0

1.5

2.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1= b

est)

Control

Extrafresh

No treatment effects No treatment effects


Figure 13 continued

Asparagus

1.0

2.0

3.0

4.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1= b

est)

Control

Extrafresh

Avocado

1.0

2.0

3.0

4.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

Extrafresh

Differences not statistically significant Differences not statistically significant

Broccoli

1.0

1.5

2.0

2.5

3.0

0 5 10 15 20 25

Storage time (days)

qu

ality

sco

re (

1=b

est)

Control

Extrafresh

Cabbage

1.0

1.5

2.0

0 5 10 15 20 25

Storage time (days)

qu

ality

sco

re

Control

Extrafresh

(1=b

est)

Difference statistically significant (p = 0.031) Differences not statistically significant

Carrot

1.0

1.5

2.0

2.5

0 5 10 15 20 25

Storage time (days)

qu

ality

sco

re

Control

Extrafresh

(1=b

est)

Cauliflower

1.0

1.5

2.0

2.5

3.0

0 5 10 15 20 25

storage time (days)

qu

ality

sco

re

Control

Extrafresh

(1=b

est)



Figure 13 continued

Celery

1.0

1.5

2.0

2.5

3.0

3.5

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

Extrafresh

Cucumber

1.0

1.5

2.0

2.5

3.0

3.5

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

Extrafresh

Differences not statistically significant Differences statistically significant to 10% (p = 0.079)

Grape

1.0

1.5

2.0

2.5

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

Extrafresh

Kiwifruit

1.0

1.2

1.4

1.6

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

Extrafresh


Lemon

1.0

1.2

1.4

1.6

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

Extrafresh

Lettuce

1.0

2.0

3.0

4.0

5.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

Extrafresh



Figure 13 continued

Melon

1.0

2.0

3.0

4.0

5.0

6.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

Extrafresh

Mushroom

1.0

2.0

3.0

4.0

5.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

Extrafresh


Nectarine

1.0

2.0

3.0

4.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

Extrafresh

Pear

0.8

1.0

1.2

1.4

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

Extrafresh


Pepper

1.0

1.5

2.0

2.5

3.0

3.5

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

Extrafresh

Satsuma

0.8

1.0

1.2

1.4

1.6

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

Extrafresh



Figure 13 continued

Strawberry

1.0

2.0

3.0

4.0

5.0

6.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

Extrafresh

Tomato

0.8

1.0

1.2

1.4

1.6

1.8

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

Extrafresh


3.3 Assessing the effect of ozone treatment

3.3.1 The effect of ozone treatment on measured ethylene levels

Figure 14 shows the measured ethylene levels within the fridges with and without the ozone generator. No effect

of the ozone generator could be observed at the output, discharge interval and frequency settings selected. The

concentration of ethylene, generally 2,000 – 5,000 ppb, was greater than the controls in the previous trial. This

presumably indicates a difference in the behaviour of the fresh produce.

Each set of data refers to measurements from an individual fridge. Measurements were made on Monday and

Thursday mornings. Fridge doors were opened for 30 seconds on Monday – Friday in the morning (after ethylene

assessment) and in the late afternoon. Doors were not opened during the weekend.

Figure 14 Ethylene levels measured within fridges with or without an ozone generator

0

1000

2000

3000

4000

5000

6000

7000

0 5 10 15 20 25

Storage time (Days)

Eth

yle

ne c

on

cen

trati

on

(p

pb

)

Control 1

Control 2

Control 3

Control 4

Ozone 1

Ozone 2

Ozone 3

Ozone 4

3.3.2 The effect of the ozone generator on product quality

The quality of each product during the three week storage period is summarised in Figure 15. The main

observations are as follows:

No clear effects on quality of produce were observed.

For apples no visible deterioration was observed throughout the storage period.


There was one commodity where there appeared to be a trend for slower deterioration in the presence of

ozone, (cucumber) and some for which the quality seemed worse with ozone (asparagus, broccoli, cabbage,

carrot, celery and grape). However, as the results were not statistically significant, this could have been

random effects due to natural product variability.

No differences in rates of weight loss were observed for any commodity (data not shown).


(grey) an ozone generator. Each data point is the mean of values assessed for produce in four replicate fridges

Apple - Braeburn

0.5

1.0

1.5

2.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

UAP

Apple - Granny Smith

0.5

1.0

1.5

2.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

UAP


Asparagus

1.0

2.0

3.0

4.0

5.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

UAP

Avocado

1.0

1.5

2.0

2.5

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

UAP


Broccoli

1.0

2.0

3.0

4.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

UAP

Cabbage

1.0

1.5

2.0

2.5

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

UAP



Figure 15 continued

Carrot

0.8

1.0

1.2

1.4

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

UAP

Cauliflower

1.0

1.5

2.0

2.5

3.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

UAP


Celery

1.0

1.2

1.4

1.6

1.8

2.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

UAP

Cucumber

1.0

1.5

2.0

2.5

3.0

3.5

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

UAP

Differences note statistically significant Differences not statistically significant

Grape

1.0

1.2

1.4

1.6

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

UAP

Kiwifruit

1.0

1.2

1.4

1.6

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

UAP



Figure 15 continued

Lemon

0.8

1.0

1.2

1.4

1.6

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

UAP

Lettuce

1.0

2.0

3.0

4.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

UAP


Melon

1.0

2.0

3.0

4.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

UAP

Mushroom

1.0

2.0

3.0

4.0

5.0

6.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

UAP


Nectarine

1.0

1.5

2.0

2.5

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

UAP

Pear

0.5

1.0

1.5

2.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

UAP



Figure 15 continued

Pepper

1.0

1.2

1.4

1.6

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

UAP

Satsuma

1.0

1.2

1.4

1.6

1.8

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

UAP


Strawberry

1.0

2.0

3.0

4.0

5.0

6.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

UAP

Tomato

1.0

1.5

2.0

2.5

3.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

UAP


3.4 Assessing the effect of SmartfreshTM treatment

3.4.1 The effect of SmartfreshTM treatment on measured ethylene concentrations

Figure 16 shows the measured ethylene levels within the fridges, with and without prior SmartfreshTM (1-MCP)

treatment. There was a trend for lower ethylene levels in the fridges containing SmartfreshTM treated products.

Each set of data refers to measurements from an individual fridge. Measurements were made on Monday and

Thursday mornings. Fridge doors were opened for 30 seconds on Monday – Friday in the morning (after ethylene

assessment) and in the late afternoon. Doors were not opened during the weekend.


Figure 16 Ethylene concentrations measured within fridges with or without prior SmartfreshTM treatment

0

1000

2000

3000

4000

5000

6000

0 5 10 15 20 25

Storage time (Days)

Eth

yle

ne

Co

nc

en

tra

tio

n (

pp

b)

Control 1

Control 2

Control 3

Control 4

Smartfresh 1

Smartfresh 2

Smartfresh 3

Smartfresh 4

3.4.2 The effect of SmartfreshTM treatment on product quality

The quality scores for produce kept in a fridge for three weeks with and without treatment with SmartfreshTM are

illustrated in the graphs below (Figure 18). The main observations are as follows.

In terms of visual quality score, SmartfreshTM treatment significantly slowed the rate of deterioration for

broccoli, peppers and nectarines, with an estimated shelf-life extension of five days and three days for

broccoli and peppers respectively.

For several products there was a trend for slower deterioration after SmartfreshTM treatment, but this was not

statistically significant (avocado, carrot, cauliflower and celery).

For other products no significant effects of SmartfreshTM treatment on visual quality was observed.

For kiwifruit, firmness measured by penetrometer after three weeks storage was significantly greater in

SmartfreshTM treated fruit than controls (Figure 17). Although this demonstrates the potential of SmartfreshTM

to slow down ripening, in this case this cannot be considered as a beneficial effect, as the kiwifruits remained

firmer than would normally be acceptable to consumers.

Internal quality was assessed at the end of three weeks for avocado and nectarines, but no differences were

observed between treatments.

No differences in rates of weight loss were observed for any commodity (data not shown).

Figure 17 Mean firmness of kiwifruits after three weeks storage in a fridge with and without prior treatment with

SmartfreshTM (1-MCP). Each data point is the mean of four fruits

0

2

4

6

8

10

12

14

16

18

Fir

mn

es

s (N

)

Controls Smartfresh treated



(grey) prior treatment with SmartfreshTM. Each data point is the mean of values assessed for produce in four

replicate fridges

Apple - Braeburn

0.5

1.0

1.5

2.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

SmartFresh

Apple - Granny Smith

0.5

1.0

1.5

2.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

SmartFresh


Asparagus

1.0

2.0

3.0

4.0

5.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

SmartFresh

Avocado

1.0

1.2

1.4

1.6

1.8

2.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

SmartFresh


Broccoli

1.0

1.5

2.0

2.5

3.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

SmartFresh

Cabbage

1.0

1.2

1.4

1.6

1.8

2.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

SmartFresh

Treatment effect significant (p<0.005) Differences not statistically significant


Figure 18 continued

Carrot

1.0

1.5

2.0

2.5

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

SmartFresh

Cauliflower

1.0

1.5

2.0

2.5

3.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

SmartFresh


Celery

1.0

1.2

1.4

1.6

1.8

2.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

SmartFresh

Cucumber

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

SmartFresh


Grape

1.0

1.5

2.0

2.5

3.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

SmartFresh

Kiwifruit

0.5

1.0

1.5

2.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

SmartFresh



Figure 18 continued

Lemon

0.5

1.0

1.5

2.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

SmartFresh

Lettuce

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

SmartFresh


Melon

1.0

2.0

3.0

4.0

5.0

6.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

SmartFresh

Mushroom

1.0

2.0

3.0

4.0

5.0

6.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

SmartFresh


Nectarine

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

SmartFresh

Pear

0.5

1.0

1.5

2.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

SmartFresh

Treatment effects statistically significant to 10% (p =

0.086)

Differences not statistically significant


Figure 18 continued

Pepper

1.0

1.5

2.0

2.5

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

SmartFresh

Satsuma

0.5

1.0

1.5

2.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

SmartFresh

Treatment effects statistically significant (p= 0.025) No treatment effects

Strawberry

1.0

2.0

3.0

4.0

5.0

6.0

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

SmartFresh

Tomato

1.0

1.5

2.0

2.5

0 5 10 15 20 25

Storage time (days)

Qu

ality

sco

re (

1=b

est)

Control

SmartFresh



4.0 Summary and discussion of findings

4.1 Fridge temperatures and normal shelf-life of produce

During the three trials described in this report to test ethylene management technologies within domestic fridges,

it was decided to set the fridges at 4°C as recommended by fridge manufacturers. Actual temperatures measured

ranged from 3.6 to 4.2°C. Table 10 shows the shelf-life of products in the absence of ethylene control

technologies for the three main trials conducted during this project. All products had a shelf-life of seven or more

days. Eight of the 21 commodities had a shelf-life greater than 21 days for all three trials, and only five

(cucumber, lettuce, cut melon, mushroom and strawberries) had a shelf-life less than the 21 days of the test for

all three trials. As it is unlikely that commodities would be kept for longer than three weeks in the home, this

could indicate that, if fridge temperatures are well controlled, the need for technologies to extend shelf-life

beyond this time may be of limited value.

However, a recent study by WRAP25 suggested that domestic fridges are generally kept at temperatures higher

than the recommendation of 4°C. A study of 48 domestic fridges found that a significant proportion of the fridges

tested (14 fridges, 29% of the sample) were operating at mean fridge temperatures of 9°C or above. Only 14 of

the 48 fridges (29% of the sample) were found to be at mean temperatures of 5°C or less, with only 34 fridges

(70%) operating below 8°C. Under these conditions faster rates of deterioration could be expected.

Table 10 Shelf-life of produce in fridges in the absence of ethylene control technologies

Product Packaging Quality score

equivalent to

limit of good

quality

Estimated shelf-life (days)

Trial 1

(Oct/ Nov)

Trial 2

(Jan/ Feb)

Trial 3

(Mar)

Apple Open bag >2 > 21 > 21 > 21

Asparagus Open bag 3 > 21 >21 18

Avocadoes Unbagged 3 14 > 21 >21

Broccoli Open bag 3 > 21 20 > 21

Cabbage Open bag 3 > 21 > 21 > 21

Carrot Open bag 2 > 21 > 21 14

Cauliflower Open bag 3 > 21 > 21 > 21

Celery Open bag 2 8 > 21 > 21

Cucumber Sleeved, cut into 2 halves 2 9 16 17

Grapes Open bag 2 13 > 21 18

Green Pepper Unbagged 3 > 21 > 21 > 21

Kiwifruit Open bag 3 > 21 > 21 > 21

Lemon Open bag 2 > 21 > 21 > 21

Lettuce Open bag 2 7 10 10

Melon Cut into 2 halves 2 7 7 7

Mushroom Paper bag 3 17 12 14

Nectarine Open bag 2 12 >21 >21

Pear Open bag 3 >21 >21 >21

Satsuma Open bag >2 >21 >21 >21

Strawberries Plastic punnet 2 13 9 9

Tomatoes Open bag 2 >21 12 >21

A score of 1 indicates optimum quality. Scores increase as quality decreases. Differences in shelf-life between the

trials are due to produce quality changes in accordance with season.

4.2 Ethylene levels in fridges

As discussed in section 2.3, at the start of this study two selections of produce were tested for their effects on

levels of ethylene within fridges (see Table 10). For selection A, considered to represent a typical domestic fridge,

ethylene concentrations were below 500 ppb, whereas for selection B, with more „high ethylene producers‟ as

expected with increased refrigeration of fresh produce, the ethylene concentrations ranged between 1,500 and

25 Reducing waste through the chill chain, WRAP, August 2010


3,500 ppb. The main trials of this project were conducted using selection B, in order to determine produce shelf-

life and the effects of ethylene control technologies in the presence of high ethylene producers. During the main

trials using selection B, ethylene concentrations measured ranged from 2,500 ppb to 4,500 ppb. It should be

noted that all these levels are high relative to average ethylene concentrations measured through the supply

chain, as indicated by Figure 19 (reproduced from research undertaken in a related part of this project26).

Figure 19 Average ethylene level measured by location within the supply chain

0

200

400

600

800

1000

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43

Eth

yle

ne c

on

cen

trati

on

(p

pb

)

Store roomsPackhousesDepotsBack of shopRetail area

Source “Ethylene levels and microbial load in the fresh produce retail supply chain” (WRAP 2010)

4.3 The effect of tested technologies on ethylene levels

Under the high ethylene levels tested, Extrafresh discs (six per fridge) reduced ethylene levels significantly from a

range of 1,000 – 4,000 ppb down to near 500 ppb. The ozone generator had no significant effect at the output,

discharge interval and frequency settings selected. SmartfreshTM treatment reduced the concentration from a

range of 2,000 – 5,000 ppb down to 1,000 - 4,000 ppb.

A review of the scientific literature27 has indicated that many commodities may be sensitive to ethylene down to

levels < 100 ppb. As this was not achieved within these trials, there may be potential to improve quality further

through ethylene control in a way that could not be demonstrated in these trials. The use of SmartfreshTM, which

works by blocking ethylene action, may provide a useful indication of the potential for more effective ethylene

control.

4.4 The effect of tested technologies on product quality for specific products

The main observations on product quality are summarised in Table 11. Only the products for which an effect was

observed have been included. A more detailed description of each of these products is included below.

26 Ethylene and microbial hotspots in the fresh produce supply chain, WRAP, February 2011

27 Reported in Ethylene and microbial hotspots in the fresh produce supply chain, WRAP, February 2011


Table 11 Effects of technologies on product quality

Product Packaging Effect of technology

Extrafresh Ozone generator SmartfreshTM

Broccoli Open bag Improved quality Improved quality

Cucumber Sleeved, cut into

two

Improved quality

Green pepper Unbagged Improved quality

Kiwifruit Increased firmness

Nectarine Open bag Improved quality

4.4.1 Broccoli

In the case of broccoli, improvements in quality were observed for Extrafresh discs and SmartfreshTM. Broccoli

kept well in the fridges and only passed the limit of acceptable quality in the ozone generator trial. A very rough

estimate of the effect on shelf-life of a technology can be made by extrapolating the quality score change on the

assumption that it changes in a linear fashion. For example, for SmartfreshTM treatment (Figure 20) extrapolation

indicates an extension in shelf-life of approximately 11 days (from 22 to 33 days from placement in the fridge),

given that the limit of acceptability is reached at a score of 3.

The scientific literature indicates that broccoli is sensitive to very low levels of ethylene <100 ppb. This suggests

that if a technology were used that could remove ethylene more effectively than Extrafresh, the benefits may be

more substantial. The SmartfreshTM results confirm this.

Figure 20 Quality scores for broccoli in control and SmartfreshTM treated fridges with extrapolation of data

1.0

1.5

2.0

2.5

3.0

3.5

0 10 20 30 40

Days in fridge

Qu

ali

ty s

co

re Control

SmartFresh

Control extrapolated

SmartFresh extrapolated


4.4.2 Cucumber

Trials indicated the cucumber quality maintenance could be improved by Extrafresh discs. Figure 21 indicates a

six-day shelf-life extension, assuming that the limit of acceptability is a score of 2. As for broccoli, there are

indications that cucumber is sensitive to ethylene concentrations below 100 ppb, so that more efficient ethylene

removal would have greater effects than we have found.

Figure 21 Quality scores for cucumber in control and Extrafresh treated fridges

Cucumber

1.0

1.5

2.0

2.5

3.0

3.5

0 5 10 15 20 25

Days in Fridge

Qu

ality

sco

re

Control

Extrafresh

4.4.3 Green pepper

The quality of green peppers could potentially be improved by treatment with SmartfreshTM. During the time scale

of the trials the peppers did not reach their limit of acceptable quality. However, extrapolation of the data

suggests that the extension of shelf-life could be 6-7 days (26 – 32/33 days after placement in the fridge),

assuming that the limit of acceptability is reached at a score of 3 (Figure 22).

Figure 22 Quality scores for green pepper in control and SmartfreshTM treated fridges with extrapolation of data

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 10 20 30 40

Days in fridge

Qu

ali

ty s

co

re Control

SmartFresh

Control extrapolated

SmartFresh extrapolated


4.4.4 Nectarine

Nectarine quality was improved by SmartfreshTM, but from existing data it is not possible to relate this directly to

a shelf-life extension (Figure 23).

Figure 23 Quality scores for nectarine in control and SmartfreshTM treated fridges

Nectarine

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 5 10 15 20 25

Days in fridge

Qu

ali

ty s

co

re

Control

SmartFresh


5.0 Conclusions

The objective of this study was to test produce shelf-life and the impact of three ethylene control technologies in

domestic fridges under the scenario of increased fridge storage of fruit and vegetables. A range of produce was

chosen that offered a “worse case” scenario in terms of likely ethylene concentrations in the fridges. This

produced conditions similar to those for which the original observations on the detrimental effect of high ethylene

producers had been made28. Under these conditions we made the following observations.

5.1 Shelf-life of fresh produce under refrigeration without ethylene control technologies

Even though the concentrations of ethylene in the fridge trials were high compared to other parts of the supply

chain, all products tested had a shelf-life of 7 or more days, with many greater than the 21 days of the trials.

5.2 Extrafresh discs

Using six Extrafresh discs, the ethylene levels were reduced from 1,000-4,000 ppb down to 500 ppb. Reduced

rates of deterioration that were statistically significant were observed for broccoli and cucumber, with some

indications for improved quality for other produce. Given knowledge of the sensitivity to ethylene of these

products, this effect could be expected to be greater if ethylene levels could be reduced further. WRAP‟s work on

the whole supply chain indicates that the produce is exposed to the highest levels of ethylene in the domestic

fridge, and although this is the last stage of the chain and therefore the effects would be less significant, removal

of ethylene may be advantageous. The technology presently on offer is, however, not efficient enough. Further

technical development is necessary, and could be valuable for waste reduction.

5.3 Ozone generation

The ozone generator had no significant effect on the levels of ethylene in the fridges at the output, discharge

interval and frequency settings selected and under these conditions. It could be that by using a “worse case

scenario” the trials moved beyond the control range of ethylene concentration for this technology. However,

ozone has other beneficial effects, including being fungistatic. The potential use of ozone throughout the fresh

produce supply chain is presently a subject of great interest and deserves more study.

5.4 SmartfreshTM

SmartfreshTM treatment slowed down deterioration in broccoli, peppers and nectarines. It had a very significant

effect on the softening of kiwifruit, although this cannot be considered beneficial at this stage of the supply chain

as the fruit was not soft enough to be acceptable even at the end of three weeks. However, these results

indicate the potential value of SmartfreshTM for maintaining fresh produce quality. Therefore, SmartfreshTM could

be more valuable earlier in the supply chain but the technology is not at a stage for it to be recommended for use

in domestic fridges.

5.5 The potential benefits of complete ethylene removal

The results indicate that for some produce, notably broccoli, cucumber, green pepper and nectarine, ethylene

control has potential to increase shelf-life. Tests with complete removal of ethylene during storage would confirm

whether under some circumstances this is a strategy that could improve handling and reduce waste

5.6 Recommendations

Work on the whole fresh produce supply chain indicates that produce is exposed to the highest levels of ethylene

in the domestic fridge. Despite this, with good fridge temperature control, but infrequent door opening, even

when using a range of fresh produce with high ethylene production, the shelf-life of all fresh produce tested was

seven days or more. This shelf-life is sufficient for most domestic households, suggesting that where fridge

temperatures are well controlled, and the increased frequency of door opening associated with normal fridge use,

the use of ethylene control technologies at this stage of the supply chain is unlikely to have great benefits and

should not be given high priority.

28 Exploratory trials conducted following previous WRAP research, Helping consumers reduce fruit and vegetable waste, WRAP, April 2008


Appendix 1 Visual scoring system

Apple

1. Bright, turgid, not greasy. 2. Less shine, slightly greasy, firm.

Note: scores above 2 are not shown as apples did not deteriorate beyond this level during the whole timescale of

trials.


Asparagus

1. Cut ends dry. Spears straight, turgid and glossy.

Tips closed and compact.

2. Cut ends disease free. Stalks turgid. Tips starting

to open.

3. Tips showing curvature and continued

feathering. Overall spears less glossy and green.

4. Extensive mould growth. Extreme tip extension.

Loss of turgidity and colour.


Avocado

1. Firm and shiny 2. Firm and shiny. Less green coloration visible.

3. Completely purple – no green colouration

remaining.

4. Purple colour darkening. Stalk scar grey.

5. Colour almost black. Mould on stalk scar.


Broccoli

1. Tight heads, blue tinge. Green leaves, firm stalk.

5. Yellowing increasing. More brown heads.

2. Heads less tight. Occasional yellowing of florets.

Outer leaves wilted.

6. Almost completely yellow

3. Increase in yellowing.

7. All florets yellow or brown. Some mould.

4. Over third of surface yellow. Some browning.


Cabbage

1. Leaves turgid and green. Cut end dry, white and

clean.

3. Increase in yellowing and root growth.

2. Slight yellowing of outer leaf edges. Some root

growth on cut end.

4. Yellowing progressing down leaf margins of outer

leaves. Heart still firm and compact.


Carrot

1. Blemish free and turgid. Clean stalk base.

2. Still turgid. Slight browning of root initials.

3. Progressive blackening of root initials. Continued shoot growth.

4. Extensive silvering. Progression of stalk re-growth and browning. Root initials

continue to blacken.


Cauliflower

1. Cut stalks white. Leaves green. Curd tight, clean and

white.

4. Remaining leaves dehydrating. Curd centre

opening out with isolated areas of browning.

2. Leaves generally turgid with laminae yellowing. Cut

ends browning. Curd still compact, white and clean.

5. Complete leaf abscission. Curd still compact away

from middle. Creamy coloured with slight peppering

and browning.

3. Some leaf loss. Remaining leaves yellowing. Curd less

compact but still clean and white.


Celery

1. Green central leaves. Stems compact and turgid with dry clean ends.

2. Stems splaying but still turgid. Base and stem ends slight browning.

3. Leaves growing. Stems more yellow with some areas of slight decay. Stem

splaying increasing.

4. Increase in browning of base. Pronounced splaying of stems. Leaves

yellowing. Progressed decay.


Cucumber

1. Turgid and firm. Dark green, disease free, no lesions.

2. Shrivel on stalk end. Still firm. Lighter green/yellow lines and areas visible. Some transport damage.

3. Stalk end extremely shrivelled. Approx. half surface area yellow. Overall scuffed and dried out.


Grape

1. Stems and berries generally green and firm.

2. Berries firm but showing browning around stalk

attachment and small areas of damage. Some stem

browning.

3. More damage and disease visible. Majority of fruit still

firm.

4. Level of disease increasing.

5. Extensive rot development. Few healthy fruit

remaining.


Kiwifruit

1. Firm and blemish free

2. Still firm. Some darker patches

visible on skin.

3. Darker patches more prevalent.


Lemon

1. Firm to touch. Peel bright, shinny and unblemished.

2. Still firm. Slightly less shinny, small isolated brown

marks evident.

3. Some skin surface deterioration and browning at stalk

end.


Lettuce

1. Cut end brown but dry. Stem tissue white. Leaves

green and turgid.

3. Progression in effects of damage. Outer leaves

yellow and wilted. Head still firm and green.

2. Some damage evident on stems and leaves. Slight

yellowing and loss of turgidity in outer leaves.

4. Significant damage and decay on outer regions.

Heart still green and turgid.


Melon

1. Firm texture. Cut surface shinny

with green outer ring and creamy

centre. No disease.

2. Cut surface showing effects of

drying.

Texture less firm.

3. Flesh level lower than outer skin.

4. Flesh increasingly sunken. Slight

mould development.

Overall texture still firm.

5. Flesh sunken. Increase in mould

development.

6. Extensive mould coverage.


Mushroom

1. Buttons tight. Cut ends white and dry. Overall colour white.

2. Some gill exposure. Overall colour off-white.

3. All gills exposed. Cut ends browning. Caps developing feathered

effect around edges. Overall colour more brown.

4. Gills fully exposed. Cut ends brown. Caps scaly and browning.

5. Dehydration evident. Disease on cut ends. Overall brown

shrivelled appearance.


Nectarines

1. Firm, shinny, no blemishes

2. Slight bruising/damage evident

3. Less shinny, increase in bruising. Some stem end

decay

4. Complete deterioration


Pear

1. No shrivel. Firm and turgid. Green colour (1.0)

3. Generally softer, riper. More yellow (2.5)

2. No shrivel, firm. Slight skin damage.

Less green

(1.5)

4. Softer. Progression in evidence of damage. Further yellowing

(3.0)


Pepper

1. Shiny, turgid, no wrinkles. Stem healthy. Dark green.

2. Less shiny. Slight browning on stalk end; minor shrivel at top.

Still firm.

3. Slightly less green. Stalk browning progressing. Still firm.

4. Some mould around stalk. Firm with wrinkles around top. Colour

changing from green to orange.


Orange

1. Firm to touch. Peel bright and shiny

2. Less bright and shiny


Strawberry

1. Berries bright and shiny, calyx green.

4. Decay advanced. Calyx blackened and dehydrated.

2. Berries slightly dull. Calyx curling/blackening. Evidence of

bruising.

5. Further increase in mould growth.

3. Appearance deteriorating. Calyx continuing to dry

/blacken.

Mould developing.

6. Substantial increase in mould growth.


Tomato

1. Calyx green, mould free. Firm and shinny.

3. Generally more red and soft. Progression of calyx

mould.

2. Calyx slightly mouldy. Firm and shiny, more red.

4. Further progression of calyx mould. Little other

visible change. Soft.

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