Fruits and vegetables play a crucial role in the human diet. It is advised to include at least five varieties of fruits and vegetable each day. A person needs a minimum of 400g of fruits and vegetables per day.
Fruits and vegetables contribute for 91% of vitamin, C, 48% of vitamin A, 27% of vitamin B6, 17% of vitamin, B3, 16% of Mg, 19% of iron, and 9% of calories. Other than that Folic acids, riboflavin, Zinc, Calcium, Potassium, Phosphorus and several anti-oxidants are supplied by the fruits and vegetables. Consumption of fruits and vegetables has proven effects on certain cancers, heart diseases, strokes and other non-communicable diseases.
SL has seasonality in rainfall resulting in two seasons, Yala (southwest monsoon) and maha (north east monsoon). According to the genetic and climatic patterns the plant crops become seasonal; for fruits major season is between April and September and the minor season is between December and February. SL has 55 different varieties of fruits that is successfully grown. Most of them are very popular worldwide due to post harvest handling, i.e. During harvesting, transporting, storage, retailing, whole sailing, processing and packaging. Post-harvest loss is defined as measurable qualitative, and quantitative food loss along the supply chain starting at the time of harvest till its consumption/other end users.
It can be quantified as measured by reduction of weight, volume or qualitatively if nutrient value, edibility is decreased. Unwanted changes in colour, taste, texture or smell accounts in to this qualitative part.
According to statistics it is estimated about 270000 tonnes of fruits are lost. Banana is the most popular and most cultivated fruit in SL, but the post-harvest loses are estimated as nearly 30%, while the papaya its about 46%, pineapples its 18%, avocado 40% and mango its 41%.
Current world population will be 10.5 billion by 2050 (UN March 2013), which will further worsen the food security issues. It accounts more 33% of humans to feed and the supply of food should be increased by 60% by 2050 to fulfil the demands. Thus the need for food availability/accessibility should be strengthened by the production, distribution and reducing the post-harvest losses.
Minimising losses of perishables is a very effective way of increasing food availability rather than increasing production, as productivity is restricted by limited water, land and weather variability.
Then to achieve a sustainable food availability to ensure food security, reducing the post-harvest losses from farm to fork is essential.
Below described are the pre harvest factors which influences the quality of fruits. Thus we have to take steps in the pre harvest state in order to maximise the quality of fruits.
Type of crops
We can select varieties of crops with improved physical, chemical and nutritious varieties of fruit crops that will yield a harvest with improved quantity and quality.
These are developed by several research centers and Department of Agriculture with the aim of attaining and maintaining good nutritional value and flavor to cope with consumer demands and to introduce resistance to physiological/pathological diseases.
Soil type-also affect the quality of the harvest.
For eg: increasing the nitrogen and phosphorus supply to citrus trees results in low acidity and low ascorbic acid levels, while increasing potassium fertilization increase them. Also pruning, thinning determines the crop load and size of the fruit, and influence the nutritional quality.
Climatic conditions
As an example if lower the light intensity it will lower ascorbic acid levels in the fruits.
Temperature influences uptake and metabolism of minerals, thus transpiration of fruits increase with high temperatures.
Heavy rains/severe water stress results in increased sunburn of fruits, irregular ripening. Moderate water stress reduces fruit sizes and increases total soluble solid content, acidity and ascorbic acid.
Causes of losses in post-harvest state affecting nutritional quality:
During harvesting
Harvesting at an incorrect stage of maturity-Maturity indices has been introduced by Institute of Post-Harvest Technology (IPHT), Department of Agriculture and ITI of SL, to identify the proper maturity during harvesting. So we need to identify the correct maturity state of different types of fruits in order to harvest at proper state of maturity, thus minimizing losses in quantity as well as quality.
Some fruits reach best quality when fully ripened at the tree, but they are usually harvested mature but not ripened.
For Eg: pineapple, lemon, oranges, mangosteen. If not done so the quality is impaired. It is better to pluck partially ripen than mature, as if fully ripened cannot tolerate the post-harvest handling. The other type of fruits ripening occur after plucking. Eg: Banana, avocados, mangoes and papaw.
Harvesting method affects composition and quality of fruits, as it causes maturity variations, extent of physical injuries etc. Thus physical injuries to a fruit increases loss of water and water soluble vitamin (especially vitamin C) loss also enhance pathological attacks by microbes, and other insects.
Damage due to harvesting devices – For harvesting there are special tools, equipments that are developed. They should be used to minimize physical damage to the harvest, if damaged it will be a focus for infection. Handlers should be trained to use these tools during harvesting.
Fruits are better harvested in the morning between 8am and 3 pm as latex is less secreted in this time and also respiration rates are low during this time. If latex is there it will cause sunburns and also it will cause mechanical damage to the fruit.
Washing after harvest is also important to remove the field heat and to remove latex; then they should be properly sorted to eliminate defects and by maturity stages/size and graded in order to increase shelf life.
Rough handling during harvesting, collecting, during loading/unloading – should be minimized. Training the laborers, minimize handling as far as possible and pack directly in the field, nails should be cut short and wearing cotton gloves can be done to minimize physical damage.
Exposure to sun/rain – Temperature and relative humidity should be kept optimum to maintain the quality and a good quantity, and to minimise post-harvest losses. For example in every 10C increase in temperature accelerates rat of loss in nutritional quality by 2 to 3 fold. Harvest should be taken to a place with minimal sunlight, then they should be washed, sorted, graded and packaged.
Also during the distribution process there is very minimal facilities to store the harvest under optimal conditions. Thus it will compromise the shelf life of each fruit type with the nutritional quality and in quantity wise. If storing for some time till transportation the temperature, relative humidity, atmospheric conditions (with low O2 and high CO2) to protect from ethylene like gases should be considered.
Packing-material should be strong enough to support the weight of the produce meanwhile should supply adequate ventilation. Poly propylene sacks are not recommended as it will compress and damage the harvest.
Tight packing also should be avoided-Install padding material on sides and bottoms of bulk packages to minimize compression damages during packing and stacking. Do not over fill the containers. Minimise drop heights when transferring. There should be ventilation holes in the packages and should pack as air can circulate. Loading/unloading also should be done carefully.
Transportation – Transportation in poly sack bags because compression damage during stacking and due to the vibration exerted on the harvest. There are reusable plastic crates that will reduce mechanical damage of fruits. Heat build up during transportation, so better to transport during nights or in the early morning thus the heat generation is minimal.
For all these the handlers should be educated and should be given the skill and needed training. During Retail sale also rough handling and exposure to unfavorable conditions occur.
Supplemental treatments to the harvest
Waxing and treatments with fungicides, heat treatments are practiced in order to increase the shelf life of fruits. For example: for citrus fruits edible form of was 0.5% bee wax, 2% cassava starch, 1% corn oil, 1% Na HC03 was experimented and found to extend the shelf life by 10 days.
There are several researches/experiments going on in wax treatments. Heat treatments are given for mangoes where they are dipped in hot water as soon as they are plucked.
Water is heated to 52C and dip mangoes for about 3 to 5 minutes which will reduce pathological disorders.
Processing – make perishables to stabilise and transported to distant locations for consumption. Processing makes them edible and add value to them.
Thus its aim should be to deliver the consumer a safe and a desirable quality, similar to the fresh product.
Research evidence shows that by the time the fresh fruits or vegetables are reaching the consumer, the nutritional values are somewhat similar to their processed products eg:canned/frozen products: Because the loss of nutrients during fresh produce in harvesting, strong and during transporting is more than we think.
To get a maximum nutritional value these fresh fruits should be consumed as soon after the harvest, unless the post-harvest handling should be optimally controlled such that nutritional losses will not happen.
We have to consider all these aspects for further development and should practice the existing proper methods in order to maximum the gain from our agricultural industry.
For that Ministry of Agriculture, Sri Lanka Export Development Board, IPHT, Industrial technology Institute, and Agrarian Research centers play a vital role in giving assistance, developing programs and training skilled handlers.
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