Project Title Prevention of Food Waste by Dual Modified Atmosphere Packaging

Problem Statement Fruits and vegetables account for 48% of the food waste, which annually accounts for

$165 billion (Gunders, 2012). One of the reasons is their rejection based on aesthetics (culling). Culling is the process of removal of food that doesn’t meet the retailer's requirements in terms of color, size, and quality. Most of the time, these less than perfect produce are perfectly edible without nutrient or taste differences. Therefore, taking advantage of those “ugly” fruits will reduce of food waste. One way to accomplish this is to process these fruits and vegetables into pre-cut, ready to eat portions, also called fresh-cut products. The overall goal of this project is to incentivize the use of imperfect produce and extend the shelf life of fresh-cut products after the package is opened, which will reduce food waste and prevent generating landfill.

Asparagus is considered as a high nutritional value vegetable. It is an excellent source of vitamin K, folate, copper, selenium, vitamin B1, vitamin B2, vitamin C, vitamin E, and so on. However, compare to other vegetables, asparagus has very high respiration rate, which means that it is more perishable than other vegetables. Also due to their thin skin, they rapidly lose moisture leading to a change in appearance that limits consumer acceptability. In the store, asparagus stems are often displayed upright in trays with chilled water, however that is not the case after they are purchased. The expected shelf life is 3 to 5 days.

Modified Atmosphere Packaging (MAP) is widely used in preserving and extending shelf life of fresh produce. However, existing MAP packaging designs can only extend the shelf life before the package is opened. Once consumers take the product home and open the package, the original modified atmosphere of the package will be interfered. Even after the package is reclosed, it would be difficult to re-modify the atmosphere by achieving the balance between film transmission rate and the produce respiration rate. Moreover, after half of the product being consumed, the respiration rate of the product will decrease considerably. The film transmission rate needs to be reduced to achieve a desired equilibrium inside the package. Therefore, our technical challenge of this is to look for a solution to reduce the transmission rate of the package after customer reclosing the package.

Project Summary Background Vegetables that respire, such as asparagus, can benefit from modified atmosphere

packaging (MAP) to slow down degradation and microbial growth. However, once the package is opened, the MAP will be destroyed. The plan for this project was to design two MAP systems respectively for before and after the package is opened. We measured changes in headspace gases, appearance and weight loss during the test.

For this project we partnered with a local retailer of the fresh asparagus and a supplier of packaging films and trays.

● Literature Review

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The fresh-cut products are more susceptive to microbial spoilage, with higher respiration rate compared to their whole counterparts, due to the wounded tissue from processing. The shelf life of fresh-cut products is decreased by browning, texture deterioration, rapid microbial growth, weight loss, and production of undesirable volatile compounds (Corbo et al., 2010).

Current packaging technologies for preserving fresh-cut product have been developed in various ways to meet extend shelf life, including multi-layer barrier films, MAP, edible coatings, gas scavengers (e.g. oxygen and ethylene) and moisture absorbers. MAP is one of the most widely used techniques for fresh-cut produce. It fills specific gas combination into the package before the package is sealed, to control the interior atmosphere (active MAP). Or utilizes natural respiration of the produce to achieve the desired atmosphere (passive MAP). By controlling the atmosphere in package, both respiration rate and microorganism growth rate are decreased. As a result, shelf life is successfully extended to meet retailers and customer needs. According to Cortellino, MAP could extend the shelf life of refrigerated (3-6 °C) fresh-cut apples (Cortellino et al., 2015).

The optimum storage conditions for asparagus are: CO 2 5-10%, O 2 >10% and a storage temperature of about 3°C with 95-99% RH (Luo et al, 2003).

● Innovative and Unique Aspects The proposed concept is to apply resealable feature to a film sealed onto tray, with

designed oxygen and carbon dioxide transmission rate to keep the modified atmosphere before opening the package. After the resealable feature is peeled open and resealed, the mislocation of the perforation on the sealing area can help reducing the film transmission rate. In this way, the re-equilibrium of film transmission rate and produce respiration rate inside the package can be achieved to extend shelf life after the package is opened. The innovative technical aspect of this project is reducing gas transmission rate to meet the demand of controlling a different atmosphere after the package is opened. As a result, the new model can protect the freshness of produce not only before the package is opened for retailers, but also after the package is reclosed for customers.

Package Configuration

Figure 1. Proposed dual modified perforated packaging

● Explanation of the proposed packaging model

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The proposed packaging system is comprised by a transparent PET tray with micro-perforated resealable film. Microperforations are registered at both the resealable area and the center area where the cut-out is. When the package is opened and resealed, the microperforations would not align on the resealable area, which results in a lower transmission rate of the whole film. At the same time, consumers take out some of the asparagus, thus increasing the headspace of the tray and reducing the required gas exchange amounts. In this way, the optimal gas composition in the package will be achieved faster comparing to the package with the original OTR (Oxygen Transmission Rate).

● Proof of concept Seven different packaging configurations were designed. Each group contained about 1 lb

of fresh cut asparagus, all originated from the same batch and tested in triplicates

Packaging Configuration Abbr. Description

No film No film No film was sealed on the tray.

Seal with perfA Perf A Film with 4 microperforations was sealed on the tray at 3rd day of storage. The package was kept through the whole experiment process.

Seal with perfA, open and reseal with perf A Reseal A

Film with 4 microperforations was sealed on the tray at 3rd day of storage. At 5th day of storage, half of the product was taken out and the package was resealed with the same film.

Seal with perfA, open and reseal with perf A/2 Reseal A/2

Film with 4 perforations was sealed on the tray at 3rd day of storage. At 5th day of storage, half of the product was taken out and the package was re-sealed with film that contains two microholes.

Seal with perfB Perf B

B groups are the same as A groups. B groups are used for destructive tests in sensory evaluation.

Seal with perfB, open and reseal with perf B Reseal B

Seal with perfB, open and reseal with perf B/2 Reseal B/2

Table 1. Experiment groups design

Relationship to Sustainability

To get food from farm to fork, it accounts for 10% of total U.S. energy budget, 50% of land usage, and 80% of consumed freshwater. However, according to the National Resources Defense Council 2012 report, 40% of food in the United States is being wasted. Specifically, fruit and vegetable account for 48% of food waste. Also, food waste is considered as the biggest single component of municipal solid waste going to landfills according to Environmental Protection Agency in 2012. According to 2015 NYC Organic Collection Report, an average household generates 10lbs of compostable food waste per month, among which food scrap takes a big proportion. The waste of food has huge environmental impact. The disposal of food waste takes up landfill space. The deterioration consumes oxygen and releases carbon dioxide and methane, which contribute to greenhouse effect. Also the high waste rate urges the farming to produce more product than real demand, which results in unnecessary utilization of resources.

An additional benefit of fresh-cut produce is that the centralized processing allows companies to easily collect food scrap and send it to composting centers. And at the same time,

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fresh-cut produce provides customers convenience by reducing the time and labor processing food at their household. With an extended shelf life, fresh-cut produce will be more able to meet customer demand for nutritious and safe produce while minimizing waste.

Processing fresh-cut produce is a value adding process. During the process, tons of water is being used to wash the fruits and vegetables. Large amounts of energy is consumed throughout distribution which leads to excessive emission of greenhouse gas. However, in considering of the utilization of innovative technologies and improvements, water consumption can be reduced by 85%; more efficient plant lightning system and high-efficiency transportation vehicles can be applied in the process (FAO, 2010, F&S Produce Co, 2016).

In 2015, 84% of total asparagus production was marketed as fresh in the US, which is 53 million pounds of asparagus (USDA 2017). Since fresh produce is one of the highly wasted products, we estimated 21.2 million pounds of asparagus are wasted (based on 40%). For example, if the implementation of our package can save 20% of the wasted asparagus, this will translate into 4.24 million pounds not thrown away, and revenues in excess of $12 million. If we extend this approach to similar vegetables the benefits can be multiplied.

Materials and Methods 1. Test 1 Transmission rate testing - Material: Roll stock transparent OPP/OPP film, thickness 1.48 mil, laser cut 0.1-0.2mm

microholes in diameter. - Equipment: MOCON’s OpTech O 2 Platinum Analyzer - Method: Dynamic Accumulation - To measure the OTR of the packaging film.

We tested five film samples to measure the relationship between OTR and microperforations. The respiratory rate of asparagus is about 60 mg O

2 /kg/h, and 60 mg C O2 /kg/h at 4 °C, which

equals 10,000 ml/m 2/ day (Chinsirikul et al.,2013). In order to obtain same OTR for the packaging film, we tested multiple films with different perforations. Since the OTR of three microperforations is 16, 714.08 ml/m 2/ day, which exceed optimum storage conditions, we decided to use the film with 2 perforations per 50cm 2 to achieve the optimum storage condition. Considering the size of the package, 8-10 microperforations are needed for the whole package.

2. Test 2 Evaluation of Mechanical Perforation Since the laser perforated OPP/OPP films are not compatible with the APET trays, and the laser perforation equipment is not available, we switched to PET films with mechanical perforation.

- Material: Roll stock transparent PET Film with a CoPET sealable layer, thickness 0.984mil, mechanical perforated with heated needle

- Equipment: Microscope - Method: Microscope Evaluation - To measure perforation hole size.

In order to achieve a consistent level of OTR of the packaging film, we need to ensure the size and quantity of mechanical microperforation meet our ideal OTR (10, 000 ml/m 2/ day).

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According to our measurements with microscope, our microperforations’ diameter is in the range of 0.2- 0.3 mm. So 4-5 holes are needed for the whole package to achieve the desired OTR.

3. Package Preparation - Fresh asparagus - 50 lbs from Wegmans - Clear APET tray - Dimensions: 7 ⅝” x 5 ⅝” x 3” - Storage Temperature: 3.5 °C - Heat sealer settings: Temperature: 122 °C, Dwell time: 1sec.

We trimmed approximately 2 inches off the bottom of the asparagus and filled each tray with about 1 lb of asparagus. Each tray was sealed with transparent PET film with a CoPET sealable layer. A summary of the 7 package type configurations can be found on Table 2.

4. Physiological Test All sample sets were subjects to three tests, including weight loss, headspace and sensory evaluation to measure the physiological changes during 22 day.

Results, Evaluation & Demonstration 1. Dynamic Accumulation for laser cut perforation:

Hole size: 0.1-0.2 mm in diameter Perforation Quantity OTR (in ml/m 2/ day)

0 3613.68 1 8844 2 10616.16 3 16, 714.08

Formula used

Table 2. Oxygen Transmission Rate of microperforated films

2. Evaluation of Mechanical Perforation (Microscope)

Table 3. Mechanical perforations sizes (in mm)

With one hole, the OTR of mechanical perforated film was 11583.84ml/m 2/ day. 4-5 mechanical perforation will be needed on the actual package to provide the target

OTR (10,000 ml/m2/ day).

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3. Weight loss Figure 2 describes the different weight losses (in percentage) that occurred over the

testing period. The small graph (top left) includes all data points, among which the samples with no sealed film has extraordinary higher weight loss than the sealed samples. The main graph focus on the sealed samples.

Figure 2. Weight loss of testing samples

Samples without seal have a significantly higher weight loss than sealed ones. This is because the open package cannot prevent the moisture from evaporating. As the weight of the packaging reduces, the fresh produce in the package is degrading quickly.

Two blue lines, representing group of Perf A and Perf B, have the lowest weight loss. This is because the perforated film has limited WVTR, and these two groups of sample have high sample weight. So the weight loss comparing to the product weight is small.

Two red lines represent groups of Reseal A and Reseal B. They have the highest weight loss. This is because the 4 perforation holes have the same WVTR with the group of Perf A and B, but the produce weight is lower than Perf A and B. So the amount of weight loss comparing with the product weight is large.

Two green lines represent groups of Reseal A/2 and Reseal B/2. The weight loss is between the red lines and blue lines. This is because these two groups have same product weight with group Reseal A and B, but less perforation (WVTR) on package, which leads to less weight loss. Some moisture in the package will escape during the open and reseal process, so these two groups have higher weight loss than Perf A and Perf B.

4. Headspace

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Figure 3 describe the oxygen concentration change in headspace change.

Figure 3. O 2% in the headspace

Two blue lines, representing group of Perf A and Perf B, have the lowest oxygen content in headspace. This is because the amount of produce is the highest among all groups, which leads to the most respiration.

Two red lines represent groups of Reseal A and Reseal B. They have the highest oxygen content in headspace. This is because the 4 perforation holes have the same OTR with the group of Perf A and B, but the produce weight is lower. The respiration was less and the OTR was relatively high, so the oxygen content in headspace was high.

Two green lines represent groups of Reseal A/2 and Reseal B/2. They have lower oxygen in headspace than Reseal A and B. The two groups had same produce weight, thus the same respiration rate. But the Reseal A/2 and B/2 has less perforation, so less oxygen can transfer from the atmosphere to packaging. Comparing with groups of Perf A and B, the Reseal A/2 and B/2 have higher oxygen content in headspace. This is because of the inaccurate estimate of the relationship between respiration and film OTR. Due to limitation of equipment and resources, we can only assume that the produce respiration rate is in linear relationship with the amount of produce, and the OTR of the film is in linear relation with numbers of perforation. In reality, those will not be simple linear relations. So it is possible that the designed perforation has a more ideal OTR, which can control the oxygen content to the ideal level.

Within the ideal range (>10%), the lower the oxygen, the lower the respiration, the slower the produce degrades. In this case, Reseal A/2 and B/2 is more ideal than Reseal A and B.

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Figure 4 describe the carbon dioxide concentration change in headspace change.

Figure 4. CO 2% in the headspace

The difference is to the opposite of oxygen content. Within the ideal range (5% - 10%), the higher the carbon dioxide, the lower the respiration, the slower the produce degrades. So in this case, Reseal A/2 and B/2 is more ideal than Reseal A and B.

5. Sensory evaluation The asparagus were evaluated at day 5, day 15, and day 22 of storage in terms of color

change, off odor, turgidity and overall quality by all team members. ● Evaluation were based on 5 points scale:

o Off odor: 5=none; 3=acceptable; 1=severe or unacceptable o Color: 5=fresh; 3=acceptable; 1=yellow (spoiled) o Turgidity: 5=fresh; 3=acceptable; 1=severe loss of turgidity o Overall visual quality: 5=excellent, extremely fresh; 4=good; 3=fair; 2=limit of

usability; 1=poor, unusable Shelf life is determined when at least one of the average scores from the three sensory quality data is less than the acceptability limit.

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Figure 5. Sensory Evaluation of Testing Samples

● Photos and explanations of four groups of asparagus

No Film

Day 5 - The sample failed as some of the asparagus observed with discoloration, unacceptable softness.

Day 15 - More of the asparagus observed with discoloration, unacceptable softness, slight off-odor, and feathered tips.

Day 21 - All of the asparagus observed with discoloration, dehydrated texture, off odor, and feathered tips. .

According to our sensory evaluation, the shelf life of no film sample is less than 5 days under refrigerated condition.

Seal with perf

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Day5 - The sample stayed fresh.

Day 15 - Some of asparagus started discolored at stem.

Day 21 - More of asparagus discolored at stem. The texture of some asparagus was failed because of unacceptable softness

According to our sensory evaluation, the shelf life of seal with perf (with 4 holes) is around 20 days under refrigerated condition.

Reseal with perf

Day 5 - The sample stayed fresh. Day 15 - The sample failed as some of the asparagus observed with discoloration, unacceptable softness, and feathered tips.

Day 21 - More of the asparagus observed with discoloration, unacceptable softness, slight off-odor, and feathered tips.

According to our sensory evaluation, the shelf life of reseal with perf (with 4 holes) is around 12 days under refrigerated condition.

Reseal with perf/2

Day 5 - The sample stayed fresh. Day 15 - The sample remained fresh. Day 21 - The sample was less fresh but still acceptable.

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According to our sensory evaluation, the shelf life of reseal with perf/2 (with 2 holes) is more than 21 days under refrigerated condition

Conclusion

Modified atmosphere packaging is an effective technology, able to significantly extend the shelf life of fresh cut asparagus while maintaining the product’s appeal to consumers. According to our experiment, our proposed MAP trays were able to rapidly alter the composition of headspace gases, thus suppressing microbial growth and maintaining the product quality in levels similar to the original values for 22 days of refrigerated storage. Specifically, the proposed containers were able to minimize the weight loss of fresh cut asparagus (0.7%) and extend the marketability of the product, versus the unpacked product (25% weight loss) to 22 days. With such a long shelf life, we have the opportunity to save up to 4.24 million pounds asparagus which worth more than $12 million annually nationwide. If we extend this approach to similar vegetables the benefits can be multiplied.

In order to explore more on this approach, we could search suppliers who are expertised on MAP packaging system and extend the experiment. Series of resealable model with laser perforation and air flushed in can be built. And more tests can be done, such as microbiological analysis, firmness evaluation, color evaluation, and sensory evaluation with large consumer panel. Besides, resealable material exploration is also critical to improve the current model.

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