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For optimum flavor and texture chestnuts should be allowed to drop to the ground when mature. This requires about two weeks for a particular variety at one location. The time of ripening varies with varietal and cultural conditions. In Connecticut, the nuts of the Japanese chestnut start to drop soon after the first of September, with the Chinese trees starting to drop later the same month and continuing until about the middle of October (Jaynes 1963). The repining date in Georgia and other southern states is the first of august, or earlier.
If squirrels or weather conditions require it the burs and nuts may be shaken from the trees just prior to shedding. In this case the burs can be collected and cracked either by hand and machine. Heavy leather gloves are required for handling chestnut burs.
Chestnuts can be easily harvested mechanically. The burs may be shaken from the trees onto well prepared ground, swept into windrows, and picked up and hulled similarly as walnuts.
Chestnuts are perishable, hence it is advisable in humid climates to collect them every two or three days. After harvesting, the nuts are cured by allowing them to dry from about 30 to 10% moisture, and at the same time develop sugars, characteristic flavor, and a desirable texture.
Mold on chestnuts may be destroyed by hot water bath. Freshly harvested chestnuts with as high as 50% incipient fungus infection may be held for two months, in perforated polyethelene bags, at 40 oF., after one hour in 125oF. water. A lower temperature or shorter time in the bath fails to destroy mold organisms, and a higher temperature of 140oF. causes severe injury to the chestnuts.
Chestnuts for export are treated with hot water, partially dried and inspected before loading. With proper ventilation, humidity control, and refrigeration the chestnuts should arrive at their destination, after 4 to 6 weeks, in good condition.
Spoilage may be prevented by proper drying. Freshly harvested chestnuts may be held for more than one year at 40oF. if they are reduced to ten per cent moisture over a period of about four days. Drying temperatures above 140oF should be avoided and the moisture content should go below six per cent. To use these excessively dry and hard meats in cooking, they need moistening by soaking or steaming for about 30 minutes.
One of the best ways of drying chestnuts is to put them in mesh bags and hold at 40oF. with well circulated air at 70% relative humidity. Under these conditions the nuts will “cure” and dry to the optimum moisture content without further attention.
A third method of preventing spoilage is to place the freshly harvested chestnuts at 30oF. At this temperature they will not mold, and will gradually dry to an optimum moisture content. Freezing will injure fresh will injure fresh chestnuts, but will not injure “cured” or hot water “blanched” chestnuts.
Chestnuts must be kept dry on the surface at all times to prevent slime and recontamination with mold. They should be held at 40oF. or lower to prevent infestation with insects. Rancidity, as with other nuts, is not a problem in storing chestnuts.