Exotic luscious fruit, Sri Lanka is famous for, be it mango, papaya, pineapple, avocado, banana or rambutan.
But how many of us even after paying exorbitant prices can get a tasty wedge of papaya or a juicy slice of mango without having black patches on the fruit.
Bent over, eye glued to microscopes such diseases in fruit as anthracnose and stem-end rot are being battled silently but meticulously by the Post-Harvest Technology Team of the Industrial Technology Institute (ITI) which had made much headway earlier not only in slowing down the ripening process to ensure a longer shelf life for fruit but also preventing the evaporation of water from the fruit to keep it fresh and non-shrivelled.
The counter to anthracnose and stem-end rot, the Sunday Times understands is a mix of herbal extracts and the simply known ITI wax.
Research into literally “stopping the rot” along with field-level trials is being conducted under a prestigious grant that the Post-Harvest Technology Team headed by ITI’s Deputy Director of Research and Development, Dr. Shanthi Wilson has won from the Horticulture Collaborative Research Support Programme (HortCRSP) funded by USAID and located at the University of California, Davis.
The team’s project which commenced in February this year was among just 15 of the 134 proposals selected by HortCRSP, the Sunday Times learns.
Under the grant of US$ 70,000 spread over a year, which Dr. Wilson sees as a “blessing” because it is difficult to secure funds for research, the 15 project teams from developing countries are being partnered by American academic groups to conduct research, training and outreach programmes to improve horticultural (fruit and vegetable) crop production and marketing. Sri Lanka’s partner is the University of Hawaii, Manoa under a team headed by eminent Prof. Robert Paull who will be in Sri Lanka this week.
The project brings together two parallel research programmes – the one at the ITI in Sri Lanka and the other, half-a-world away in Hawaii.
Here we are conducting research on how a natural coating and essential oils will control post-harvest diseases in fruit and vegetables while in Hawaii they are using natural epiphytic micro-organisms for the same purpose, explained Deputy Director Dr. Wilson.
For Sri Lanka, it all began with a scientific assessment in the early 1980s that post-harvest losses in fruit and vegetables were phenomenal, as much as 40-60%, it is learnt.We have the fruits and the vegetables but by the time they reach the consumer or exporter there is nothing much to salvage, she says, stressing that the picking and the handling after the picking leave much to be desired.
The fruits are picked, kept in the hot sun and stuffed into lorries, while the pickers themselves stand on the mounds of fruit, she says describing what she has seen at ground level. Even if packed into gunnies, people sleep, stand or sit on them while transporting them. They are squashed, crushed and damaged.
On top of that came scandals such as carbide in mangoes which cast a blight on the fruit industry in the country, with many in shock after hearing that Calcium carbide, a chemical hazardous to human health, was being used to quicken the ripening of fruit, although it is a banned substance.
The labours of the Post-Harvest Technology Team, however, paid off when three years ago they developed a natural wax, not injurious to human health, which could slow the ripening process prolonging the shelf-life while also preserving the freshness of the fruit, especially mango and pineapple, the Sunday Times learns.
Commending the National Science Foundation, the Council for Agriculture Research Policy, the National Research Council and the Science and Technology Ministry for supporting their research programmes, Dr. Wilson gives a simple botany lesson to explain the outcome of the application of the wax. Ripening makes a fruit which is often green, sour, odourless, hard and mealy, soft, juicy, sweet, fragrant and colourful. The skin-colour changes as chlorophyll (the green in plants) is broken down and sometimes new pigments or colours are made.
This also means that the acids which make the fruit sour are broken down, the mealy starches are converted to sugar, hard pectin is softened and larger molecules are made into smaller ones that come out as aroma, she says, adding, that it follows a “ripening signal” initiated by a burst of ethylene gas. The ethylene indicates to the genes present in the fruit that it is time to release the enzymes that cause ripening.
This ripening signal is unique, it is learnt, because it involves the airborne natural hormone – ethylene, which is produced by rapidly growing tissue like the tips of some roots, flowers, ripening fruit, damaged tissue etc., with ripening being set off by the simple act of picking a mature green fruit.
The wax, initially used on pineapples, restricts the production of ethylene, delaying the ripening process while also preventing the water, which forms 90% of a fruit, from evaporating thus stemming the wrinkling and the rot that sets in thereafter, explains Dr. Wilson, stressing that unlike carbide which produces acetylene, ethylene is a natural ripening agent. Only about 2ml of wax is needed for 2,000 kilos of fruit.
Next comes the other serious issue of bacteria and fungi that attack fruit and vegetable and that’s what the grant is being utilized, to stymie the rot under the active participation of the Post-Harvest Technology Team members, Chamila Wijesinghe and Shiranthi Perera and research assistant Shyamen de Silva.
Mango grown in smallholdings like home-gardens seems to be particularly vulnerable to these pathogens (micro-organisms) which may get in as early as the time of flowering. Papaya too can be invaded by water-borne spores which ultimately end up in the fruit after having got into the flowers, says Dr. Wilson.
While the wax which slows ripening by restricting ethylene performs a dual task in that the pathogen spores also need this gas to grow. Therefore, restricting its supply will create a hostile environment for these bad spores as well, it is learnt.
Why can’t chemicals including pesticides and fungicides be used to curb such diseases as anthracnose and stem-end rot?
“They shouldn’t be used as they are harmful to humans,” she says, adding that her team is researching on using a non-chemical methods to combat these bugs, and is working with Link Natural Products Pvt.
Field trials on a large-scale are to be carried out, with laboratory testing already indicating success – an 80% reduction in post-harvest losses, with people seeing tempting pieces of mango or papaya on their plates without those ugly black patches.
Workshop on fresh produce
A workshop on ‘New trends in minimizing losses via safe and environment-friendly methods of handling fresh produce’ organized by the Post-Harvest Technology Team will be held on August 12 at the Galle Face Hotel.
The guest speakers are Prof. Robert Paull and Dr. Nancy Chen from the University of Hawaii at Manoa.
Registration details may be obtained from ITI Deputy Director Dr. Shanthi Wilson, Phone: 011-2379800 ext 311
or email: padmini@iti.lk
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