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Post Harvest Activities of Jatropha curcas
Plucking of Fruits: Fruit harvesting is important in order to obtain a good product. Attention should be paid to several aspects. These are harvesting criteria, harvesting technique, drying and seed storage.
Harvesting Criteria: Fruit harvesting is performed after the fruits mature. This takes 90 days after flowering. A matured fruit is indicated by the change in color. It changes color from light green -> brownish yellow -> golden yellow -> black -> dried fruit. Other indicator is that the fruit skin is partly opened naturally. When the fruit skin is opened, it means that the seeds inside are already mature. If harvesting is done too early, the seeds will have lower oil content, and if it is too late, many seeds will fall to the ground.
Harvesting Technique: Harvesting is done by hitting the branch and the dry fruit is forced to fall on the ground. This technique is not effective. The best way is to pick the fruits directly from the branch. The maturity in a group of fruits is not uniform. If 50% of the fruits in one group are matured, then this technique can be used, that is by cutting the stalk of the fruit with sharp knife. If the fruit is at higher level, a long stick with a small pocket at the tip can be used.
Fruits should be plucked at appropriate time and in appropriate manner. Plucking time in India, is generally at the end of December or beginning of January. All the fruits on tree are not ready for plucking and only ripe golden yellow fruits should be carefully plucked and put in baskets. Care should be taken not to break the branches and leaves, while plucking. Once first lot is picked up, it helps other fruits to ripen. If these are not plucked, these dry on trees and fall down if tree is shaken. It can then be collected from floor. Latex drops down from the point of plucking of fruit and care should be taken that it does not fall on body.
Drying of Fruit and Seed: If the seeds are to be used for producing seedling, the drying of fruits is carried out in shade. It should retain 5 to 7% moisture. Direct sunshine may give negative effect on the fertility of the seed. But if the oil is to be extracted from the seeds, then direct sun drying can be performed until all fruit are opened naturally. After all fruit skin is separated, the seed should be dried again for one day. If the seed is not dried enough, it will be attacked by molds and can get easily damaged. It should be dried until the moisture content 1 to 2%.
Seed Storage: The seeds with 5 to 7% moisture content should quickly be stored, in a plastic bag. The pile of the plastic bag in the storage house should not directly receive sunshine and also should not directly touch the mud floor. Storing the seed for seedling at room temperature can prolong the storage up to one year, but it is recommended that the storage of seedling seed not longer than 2 months.
If Jatropha curcas seeds have high oil content, storage should be done for a short time, and if it is possible, the already dried seeds should be processed right away to avoid increase of free fatty acid.
The golden yellow fruits are dried by sunlight. These are then sorted in four grades as per their size. These dry fruits are then pressed by flat wooden boards. The seeds are thus separated from skin. Skins are separated from seeds and are burnt as fuel or for mulching. These seeds are then stored in cool dry place in bags.