HARVESTING OF FRUITS AND YIELDS
Lychee being a non-climacteric fruit requires to be harvested after attaining full maturity on the tree. Studies have been conducted to determine the maturity standard for different cultivars under different agro-climatic conditions. Fruits have a sigmoid pattern of growth. First the pericarp develops, then the seed and aril is formed and the seed turn from green to brown. During maturity acidity declines and TSS increases which corroborate the appearance and colour on the fruit. Thus, the colour of fruit is an important criteria to decide the harvesting stage (Singh and Yadav, 1988). The red pigmentation in lychee is associated with anthocyanin pigments (cyanindin-3-glucoside, cyanindin-3-galactoside, pelargonidin-3-glucoside and pelargonidin-3, 5-diglucozide), which develop better in the direction of good light penetration. Invariably pericarp colour and smoothness of pubicles are the best indicators (Singh and Yadav, 1988). Depending upon the cultivar, 65-80 days are taken for maturity from fruit set.
The fruits are harvested in bunches along with a portion of the branch and a few leaves. At the time of harvesting care is taken to harvest the selected bunch, which has attained the desirable maturity as determined by colour development and taste of the pulp. For distant market fruits are harvested when TSS attains 19° Brix and acidity 0.3 to 0.4 percent. The fruits are harvested early in the morning when temperature and humidity are congenial, to have longer shelf-life of the fruit. At the time of harvest fruits are collected in a manner so that they do not fall on the ground. Use of mechanical tools for harvesting is practiced. The harvesting period is generally May-June, depending upon cultivar and location.
The yield of lychee varies according to the age of the tree, agro-climatic condition and maintenance of the orchard. Usually about 80-150 kg fruit/tree is obtained from 14-16 year old trees. However, from a fully grown tree a yield of 160-200 kg/tree has also been recorded. Apart from a management practice, bee keeping in lychee orchards has been found to increase the yield of quality fruits by 15-20 percent, since lychee needs cross-pollination. Apis mellifera is the commonly used bee in lychee orchards, which also provide additional income from honey.
Lychee deteriorates very fast after harvest. Pericarp browning is a major post-harvest problem, which renders the fruit unmarketable. Browning is associated with desiccation. Peroxidase activity coupled with ascorbic acid oxidation enhances anthocyanin degradation. Techniques to reduce browning and maintain the red colour and prolonged storage life include sulphur treatment and packaging in perforated plastic bags and storage under cold conditions. Sulphur dioxide (S02) fumigation is used as a post-harvest treatment to reduce browning. SO2 treated fruits have a bleached pericarp which turns uniformly pink in colour after 2-3 days. Fumigated fruits absorb 30-65 percent of applied SO2. There is increasing concern about the residue of sulphur and the residual limit is only 10 ppm. For sea transportation 600-650g sulphur is recommend for the duration of 50-60 minutes, while for air transport 300-400 g sulphur for 30 minutes are advocated. The Agricultural Produce Export Development Authority (APEDA) has developed a procedure for production of quality lychee. The steps are: production > inspection of farm > harvesting > desolating and sorting > receipt at packhouse > acceptance of produce > sorting and grading > sulphur treatments > packing and cooling > palletization > storage > container loading and transportation.
Aril breakdown or softening of the aril involves a loss of turgidity and translucency where fruits become blunt in taste. The disorder starts near the pericarp and is prevalent at the end of the stem. Post-harvest decay also occurs due to bacteria, yeast and fungi. Lychee browning and fungal contamination is prevented by dipping fruits in hot benomyl. Since this chemical is being restricted from use, alternative methods are desirable. Irradiation of fruit is considered to reduce browning and post-harvest losses. Storage temperature of 2-5°C is considered to extend the shelf-life. Use of perforated polythene bags and storage at 3°C have also been reported to increase shelf-life. Controlled atmosphere storage is considered better for maintenance of the freshness of the fruits. Thus, to have better post-harvest life of fruits, careful harvesting, pre- cooling, transportation in cool van, sulfuring and storing at 2-3°C would be essential.
Processing of lychee is done in different forms. Canning of pulp, aseptic packing and ready to serve lychee juice are common. Dried lychee processing is not in practice. Pulp of lychee is aseptically packed and stored at 2-3°C for preparing lychee juice.
A substantial amount of lychee produced in the country is consumed locally. Lychee, being highly perishable, is available for very short duration. Marketing of fruits is done in different forms. Growers rent their orchards to contractors, who in turn harvest and sell to local markets.
In chains of marketing increased numbers of middlemen reduces the share of growers in the price of produce paid by consumers. Generally, for the domestic market lychee is packed in 10 kg boxes or baskets having a lining of lychee leaves. There has been considerable importance given to the packing of lychee for niche domestic markets. Now lychee is packed in 2-2.5 kg boxes and transported in cool-chain. The exportable lychee is packed in 2 to 2.5 kg or 5 to 6 kg boxes after sulphur treatment.