R.O.P. film development offers potential for many more products

R.O.P. has new packaging for lychees and persimmon that will not only eliminate post-harvest chemical interventions but also significantly reduce post-harvest losses, extend shelf life and, incredibly, improve the taste of both fruits

The new additions from R.O.P. will become part of the ExtendCast^TM products portfolio, used for a wide range of salads, fruits, vegetables and herbs all over the world. The company believes that its science-based packaging solutions can have a similar impact on additional exotic fruits.

In 2015, Produce Business UK spoke to Gal Wollach, the vice-president of international sales at R.O.P. He works alongside customers to develop product-specific Cast Polypropylene (CPP) film, bags, and converted products. Wollach decried the acceptance of waste in the supply chain and called for buyers to adopt a joint scientific approach to optimise the performance of the products that pass through the supply chain, before ending up in the kitchens and fruit bowls of their customers.

We also spoke with Paul Summers, the UK sales director, about his on-going shelf life extension trials at numerous customer sites.  The aim of these trials is to identify areas for improvement and enhancement of the post-harvest performance of a wide range of fresh produce in the UK. Summers is certain that R.O.P.’s product solutions  will play a big part in revolutionising the UK supply chain in the next few years.

Lifting the lychee limits

Lychee is harvested at full maturity. When ready for picking, a lychee is round and reddish in colour. As the fruit ages on the tree, the skin becomes thinner and micro-cracks can develop across it, which is one of the traits that typically lead to accelerated fruit post-harvest dehydration. 

Optimal temperature for the storage and transportation of the fruit is 2-4°C (36-39°F) and the recommended relative humidity is 90-95%. Both of these conditions are extremely important for the prevention of dehydration and browning of the skin.

“If you take a lychee and leave it as it is for two weeks or more (less than the time it takes to transport it from where it is grown to the marketplace),” says Summers, “it’s skin will be brown, not red. It will still taste nice and sweet, but no-one will buy it.

Consequently, the contemporary typical post-harvest treatment includes application of a chemical treatment aimed at preserving the colour of the fruit. That treatment usually involves bleaching followed by the use of a diluted acid solution dip (using hydrochloric acid; phosphoric acid or citric acid). The acid treatment brings back the reddish skin colour, which is of course desired both by consumers and those along the supply chain who want to sell the fruit to the consumer.

Whilst it does the job and preserves the colour of the fruit’s skin, the clear downside of this preservation methodology, says Summers, is that it results in an “undesirable aftertaste”. The method is also banned from use in several countries. “This is clearly a concern, but because they look good, people will buy them even though they won’t have the best experience eating them.,” he says. “With lychees, which are not a widely consumed fruit in the UK, it is very difficult to increase sales and the frequency with which people purchase if they do not have a good eating experience.”

R.O.P. took this into consideration when it designed ExtendCast^TM Lychee – a bag that it has proven will keep lychees in prime state and the skin of the desired colour for more than two months in storage and under point-of-sale conditions, while obviating the use of chemical bleaching, which in turn results in better tasting fruit.

Multiple, independent, blind taste tests have been conducted and the results of these confirmed that no off-flavour or after-taste was noted. The fruit flavour and aroma was described as fresh, natural, juicy and sweet, and distinctively better than commercially chemically treated fruit. On the other hand, the traditional, chemically treated fruit was referred to as ‘spoiled’ and ‘sour’ when taste tested alongside ExtendCast^TM lychee packed natural fruit.

Summers says: “We have a bag that we have proved can keep the lychees for 60 days with no chemical treatment whatsoever. We have done a lot of blind tasting with the fruit and people say ‘wow, this is what lychees are supposed to taste like’.”

During its trials, R.O.P. packed moist, room-temperature fruit into ExtendCast^TM bags and they were heat sealed. Bags were then placed in master cartons and put into cold storage at the prerequisite 2-4°C (36- 39°F) for the duration of the required storage time.

The film’s Oxygen Transmission Rate (OTR) was calibrated to accommodate a variety of temperature regimes using modified atmosphere packaging for domestic and export logistics. For extended storage periods of 21-28 days, that was be a stable 2-4°C and for shorter storage of 8-10 days, this was 16-18°C (60-64°F).

R.O.P. has also proven that weight loss can be kept at a minimum using the ExtendCast^TM bags, says Summers, which also has a positive effect on preserving the fresh appearance of the peel. Comparing the two storage conditions, only slightly greater weight loss was noted with the fruit that was stored in ambient conditions compare to cold storage, but this was still far lower than would have been expected for fruit that was not packed in ExtendCast^TM bags.

See the table here. 

Pepping up persimmon

The same effects have been achieved with sharonfruit, or persimmon, he adds. “The industry needs to extend the storage life of persimmon in order to bridge the existing supply gaps between northern and southern hemisphere supplies,” says Summers. “There is also a financial incentive, as longer storage regimes mean that more of the fruit can be shipped by sea to destination markets, thereby reducing the logistics costs.

“Incorrect storage and handling practices have been shown to significantly reduce the firmness of the fruit, as well as increasing the incidence of Alternaria, which causes skin rot and splitting. In developing what has now become FreshCast^TM Persimmon, we set out to identify a better way to store the fruit and get it to the consumer in the optimum condition.”

The optimal temperature for the storage and transportation of persimmon is 0°C (32°F). Alongside this, the recommended relative humidity, as with a lychee is 90-95%. The respiration rate at this temperature are around 2-4ml CO₂/Kg per hour within this storage regime.

Ethylene is produced at >0.1 μl/Kg per hour at 0°C and at 0.1-0.5 μl/Kg per hour at 20°C (68°F) and this is significant because it is well known that persimmon is highly sensitive to ethylene, and that exposure to ethylene results in a rapid decrease in fruit firmness. The search for a treatment that would prevent the effect of ethylene was the first step to tackle this challenge for the industry and the application of 1-MCP was found to be effective at preserving the firmness of fruit that was later stored at 0-1°C for up to 5 months.

For astringent varieties such as Triumph, various methodologies are used with the most common one being exposure of the fruit, before it is shipped to the market, to high CO₂ and low oxygen conditions for 24 hours (achieved by a gas flush of 80% CO₂ into large containers). This treatment makes the tannins soluble and therefore the astringent effect is prevented.

Persimmon had previously responded well to Modified Atmosphere Packaging (MAP) with low oxygen and CO₂ held at 5-8% helping to delay ripening and retain freshness and firmness, as well as reducing chilling injuries. The fruit that was shipped using MAP, however, was proving very susceptible to Alternaria, and unmarketable for more than a few days in ambient temperature. That fruit was being repacked in destination markets at the cost of the shipper or the importer.

To solve this issue, FreshCast^TM Persimmon R.O.P., in collaboration with the Laboratory for Storage of Fruit and Israeli grower/exporter Mor – Sharon Fruit, set to work.

Samples of unripe, 1-MCP treated, Triumph persimmon were placed for three months in cold storage at 30-32oF, then for seven days at shelf simulated conditions of 68°F. One sample was packed in FreshCast^TM Persimmon, while the other was left ‘naked’. The fruit packed in FreshCast^TM Persimmon remained firm, presented clean skin and had no astringency when it was stored as if on-shelf. The fruit that was stored naked turned soft, developed extensive infection by Alternaria and remained astringent during the shelf simulation stage of the test.

R.O.P’s results suggest that the use of FreshCastTM Persimmon vs. naked persimmon in trials worked best when combined with MAP. It would allow fruit to be stored for up to five months, with little or no waste and far better firmness and disease resistance. 
The R.O.P.-Mor co-operation has developed a flexible MAP solution that addresses challenges that had previously prevented off-season long-distance exports of persimmon. A protocol combining 1-MCP treatment with storage at 30-32oF (-1-0°C) allows for storage of persimmon fruit for 3-4 months while in the harvesting bins. When ready for sale, the fruit is been sorted and graded then packed into FreshCast^TM Persimmon, which further protect the fruit through distribution.

Three key observations were made:

• Astringent fruit naturally turned ripe;

• Alternaria was not observed;

• The fruit remained firm during shipment and shelf life simulation.

See the results here.

Summers says: “This is the perfect example of how we work with the entire supply chain to create synergies that work for everyone.  This solution is already making a real difference commercially and we will continue to work with Mor and its customers to fine-tune the science and the logistics practices to ensure that the performance of FreshCast^TM Persimmon matches the high expectations of everyone from grower to consumer.

“We knew we had succeeded when a group from the UK came over to Israel to see us and we showed them what we were doing with persimmon. They genuinely didn’t know that this was what persimmon could taste like until they tasted fruit that had been in our bags. Not many people in the industry do and when you extend that to the consumer’s lack of knowledge of the true taste of persimmon, it’s clear to understand why this is a problem.”

R.O.P is an exhibitor at the London Produce Show and Conference on June 9. Register now to come and see Paul and Gal, who is also delivering a seminar on the same day at the Grosvenor House, Park Lane, Mayfair.