(a) To develop methods of optimum harvest maturity, post harvest handling, disease management and standardised packaging for three new tropical fruits (lychee, rambutan, casimiroa).
(b) To determine optimum conditions for forced air cooling and temperature management of these packs for long-distance non-refrigerated and refrigerated transport.
(c) To evaluate domestic and export market reaction to this postharvest technology.
Chemical products reported in this review are not recommended for commercial use. Postharvest chemical usage is currently controlled by strict government legislation. It is illegal to use any chemical product for which specific registration does not exist.
1. That the brix: acid ratio of the pulp be commercially adopted as an index of fruit maturity, with fruit possessing an average brix: acid ratio below 35 deemed immature. (Commercially adopted, 1 December 1989).
2. Lychee fruit should be held at 5°C when stored for up to two weeks or 7°C for periods in excess of two weeks. (Currently recommended by field extension officers).
3. Retention of the desirable red skin colour is heavily dependant on preventing fruit moisture loss after harvest. Suitable packaging (e. g. plastic punnets, either snapshut or overwrapped) will retain skin colour. Waxes will require further investigation.
4. Sulphur dioxide fumigation followed by low pH dipping may have commercial benefit in controlling postharvest skin browning. Residue assessment and monitoring is still required.
5. Harvest fully mature fruit. Grade out blemished or insect-damaged fruit. Immerse in hot benomyl (Benlate 50 DP 1 g/l) for 2 min at 48 to 50°C. Allow fruit to cool before grading or packing. Cool fruit to 50°C as soon as possible after harvest, and store in the recommended packaging.
6. Benomyl powder (Benlate® DF) should first be made into a slurry before adding to the dipping tank. Do not add the powder directly (Benlate DF mixes more readily than Benlate®WP). Maintain benomyl concentration within the required range through topping up half way through the packing run with additional benomyl. Maintain water level with a suspension of the same strength as the original dip.
7. Vigorous agitation before and during dipping by means of a powerful, recirculating pump is recommended to keep the fungicide suspended. This is preferable to stirring or paddling. The temperature of the dip must be monitored regularly, and tank agitation is important for maintaining even heat distribution.
8. Once the dip becomes contaminated with dirt and debris, or after 2 days continuous use, it should be replaced. Pre-washing fruit helps prolong dip life. Dispose of the used dip suspension in a 100 cm deep trench filled with stones.
1. Cool storage of fruit will increase postharvest storage life to 14 days. In the absence of cool storage fruit will turn brown within 4 days of harvest.
2. Rambutan produce relatively low levels of ethylene. External application of ethylene had no effect on browning or storage life.
3. Fruit should be stored under high relative humidity (RH) to prevent drying and shrivelling of the spinterns, which leads to browning of the skin. The optimal RH for storage is 95%.
4. Yellow-skinned cultivars are more like to illustrate injury than the darker red-skinned types.
1. Casimiroa should be cool stored at 10 to 15°C.
2. Casimiroa harvest maturity is extremely difficult to determine with no clear index developed.
3. Fruit lose moisture rapidly after harvest. Packaging to reduce dehydration will increase storage life.
4. Fruit fly infestation is a problem with this crop. Grower instruct in correct field control procedures will reduce postharvest damage.
5. Fruit respiration and ripening is very rapid. Fruit may go from hard green to soft and over-ripe in one or two days. CA technology to reduce respiration may be an area for further work, and should be investigated.
DATE: July 1991
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