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Postharvest losses of fruits and vegetables in case of Sri Lanka

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Sri Lanka is a tropical island with 46 agro-ecological zones and two monsoon seasons. This facilitates the cultivation of a variety of long-lasting and perishable crops. Crop production, on the other hand, is frequently seasonal and dependent on water availability. This leads to overproduction soon after harvest, followed by scarcity and high market prices during off seasons. In Sri Lanka, 70% of population lives in rural areas, and agriculture provides livelihood for approximately 40% of them. The agricultural marketing process in the country is a complex operation due to services and functions involved in moving a crop product from where it was produced to where it would finally be consumed.

Postharvest technology involves all treatments or processes that occur from time of harvesting until the foodstuff reaches the final consumer. Efficient techniques for harvesting, transportation, handling, storage, processing/ preservation, packaging, marketing and utilization etc. are components of the postharvest chain. The postharvest system encompasses a sequence of activities and operations that can be divided into two groups.

  1. Technical activities – harvesting, field drying, threshing, cleaning, additional drying, storage, processing
  2. Economic activities – transportation, marketing, quality control, nutrition, extension, information & communication, administration & management

Harvesting of fruits and vegetables

Fruits and vegetables are frequently harvested either at an immature or advanced stage of maturity. Immaturely harvested fruits do not naturally ripen, and if they do, the quality characteristics are extremely poor. When fruits are harvested before or after their proper maturity period, natural physiological processes make them more prone to harm and damage during harvesting, sorting, grading, and transportation.  Although it is normal practice to harvest the bulk of vegetables at an over-mature stage, postharvest losses are severe then.

Common low country vegetables are eggplant, okra, pumpkin, tomato, bitter gourd, snake gourd, long beans, onion, leafy vegetables, luffa, drumstick, capsicum, etc. Harvesting of low country vegetables is done on seasonal basis. Upcountry vegetables are leeks, beans, cabbage, beetroot, carrot, and potato etc., cultivated in upcountry wet zone more intensively under rain-fed or irrigated conditions at high altitudes. The cultivation is staggered and harvesting is generally carried out throughout the year.

The main fruits grown in Sri Lanka are mango, papaya, pineapple, avocado, banana, watermelon, rambutan, mangosteen, wood apple, guava, pomegranate and jackfruits. Banana, pineapple and papaya are cultivated commercial-scale whereas other fruit varieties such as mango, wood apple, guava, pomegranate, avocado, etc. are supplied mainly from home gardens. Moreover, a considerable proportion of the supply of banana, and papaya is coming from home gardens as well. And considerable amount of tropical grapes and oranges are cultivated in Sri Lanka. However, the local demands for certain temperate fruits such as apples, oranges, grapes and dates are met through imports.

Sri Lanka is a tropical island, where temperature and humidity levels of the environment are relatively higher. Exposure of perishable fresh produces such as fruits and vegetables to high temperature and RH just after harvesting is highly unfavorable and lead to initiation of rapid deterioration. In fact, temperature is the single most important factor affecting the deterioration rate of freshly harvested commodities. Proper relative humidity (RH) is also required to be maintained to reduce weight loss and freshness during storage.

However, at present, temperature & humidity-controlled storages facilities of sufficiently large scale are not available as a service. This situation leads to waste of harvest when there is a surplus of local supplies, where remaining fruits and vegetables are just disposed as garbage by farmers, collector, whole sellers and retailers. Therefore, large heaps of waste fruits and vegetable could be observed seasonally near wholesale markets etc.

Chain practices and postharvest losses

The annual loss of fruits during postharvest operation represents about 210,000 metric tons of fruits, which is about 30 %– 40 % of the harvest, representing approximately US$ 90 million losses in financial terms. Annual loss of vegetables during post-harvest operations is quantified about 370,000 metric tons, which is about 20% – 40 % of the total harvest. This represents approximately US$ 110 million.

Processes of cold chain procedures for fruits and vegetables have been accepted as right, where the operations and processes contribute to a reduction in postharvest loss in the fruits and vegetables produce chain. Some cold chain steps, however, may not be necessary depending on the type of fruits and vegetables. And, careful handling of the produce, as well as appropriate temperature and humidity management in storage, are vital parts of the process to avoid losses.

Figure: Post harvest handling and cold chain practices

In rural farming, the issues of lack of awareness of market dynamics, lack of knowledge on good practices and economically beneficial procedures such as sorting, grading, precooling, not having access to a well-coordinated transport system that reduces processing and waiting time of produce etc. are major issues that contribute to substantial fraction of the overall postharvest losses.

Implementing suitable post-harvest activities such as sorting, grading, and pre-cooling, as well as enhancing storage facilities to preserve the basics of decreasing handling waste appear to be promising steps in improving the status quo of the current postharvest process. In this regard, a solid government policy and regulatory enforcement in postharvest processing, storage, and transportation aspects will undoubtedly ensure that government subsidies for farmers are better utilized at the grassroots level.

In order to reduce postharvest losses of fruits & vegetables, it is very much required to provide temperature & humidity-controlled storage systems, which control the rate of deterioration of fresh produce. This certainly extends shelf-life of fresh fruits and vegetables within possible limits but it’s also decided by other postharvest operation such as incorrect harvesting before reaching correct maturity, improper handling procedures in the field, improper packaging at various stages of the process, and improper transportation and incorrect retail selling approaches are some of the major reasons for such high postharvest losses. Total postharvest damage due to above mentioned reasons are cumulative and finally affect the quality and durability. Further, storage life of fruits and vegetables could be extended greatly by removing the field heat just after harvesting. Suitable field operated or convenient cooling systems are needed to remove field heat from fresh produce before going to storage.

In general, temperature and humidity play major role in reducing postharvest losses of fruits and vegetables during most part of the postharvest channel. Low temperature and proper relative humidity are required to be maintained in order to reduce metabolic reactions, weight loss and freshness of fruits and vegetable. During storage, low temperature reduces microbial activities too. 

In order to increase the effectiveness of postharvest process handling of fruit and vegetables, appropriate corrective measures targeting small scale producers as well as commercial scale producers need to be popularized and practiced. At small scale producer level, promotion of appropriate low-cost postharvest practices and procedures, facilitating low-cost cold chain elements and user-friendly information flow mechanism on market situation would certainly help avoid some of the steps that lead to losses. Monitoring system of commercial postharvest handling process that ensure scientific bulk handling, storage and transportation of fruit and vegetables, properly designed economic centers with well-regulated environment-controlled storages etc. would greatly reduce losses in bulk handling, ensuring better food security in the island.

References:-

Annual report, Central bank of Sri Lanka. 2018.

Democratic Socialist Republic of Sri Lanka – Data Collection Survey on Agricultural distribution network and marketing – Final Report. Japan International Cooperation Agency System Science Consultants Inc.

Gunathilake DMCC, Tiwari AK, Tharanga Kahandawala KA. Efficacy of washing treatment for extending the post-harvest shelf-life of papaya (Carica papaya). Int J of Chemical Studies. 2018;6(4):229–635.

Gunathilake DMCC, Tiwari AK. Evaluation of Efficacy of Washing Treatment for Extending the Post-Harvest Life of Tomato (Solanum lycopersicum L). Int J Curr Microbiol App Sci. 2017;6(11):1999–2004.

https://hasanuzzaman.weebly.com/uploads/9/3/4/0/934025/postharvest_technology.pdf

Kader AA. Postharvest Technology of Horticultural Crops. 3rd edn. Division of Agriculture and Natural Resources, University of California, Davis, CA. Puvlication No.3311. 2002.

Kitinoja L. Returnable Plastic Crate (RPC) systems can reduce postharvest losses and improve earnings for fresh produce operations, PEF White Paper No. 13-01, The Postharvest Education Foundation, Oregon, USA. 2013. 1–30.

Kitinoja L. Use of cold chains for reducing food losses in developing countries, PEF White Paper No. 13-03, The Postharvest Education Foundation, Oregon, USA. 2013:1–16.

Kitinoja LS, Saran SKR, Kader AA. Postharvest technology for developing countries: challenges and opportunities in research, outreach and advocacy. J Sci Food 2011;91(4):597–603.

Leyte JC, Forney CF. Optimizing flat design for forced-air cooling of blueberries packaged in plastic clamshells. Journal of Hort Technology. 1999;9(2):202–205.

Rajapaksha L, Gunathilake DMCC, Pathirana SM, et al. Reducing post-harvest losses in fruits and vegetables for ensuring food security – Case of Sri Lanka. MOJ Food Process Technols. 2021;9(1):7-16. DOI: 10.15406/mojfpt.2021.09.00255

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