In order for chestnuts to taste their best, they must be stored and cured properly:
Storing Chestnuts—Chestnuts should be stored in their “fresh state”—just as they come off the tree. Chinese chestnuts can be stored up to six months this way (European and Japanese chestnuts usually spoil after a month or two of storage).
Three Requirements for Storing Chestnuts
Cool Temperatures (but not freezing!) 34 F to 38 F is ideal. Chestnuts will freeze and be ruined at about 25 F.
Prevent Moisture Loss—This may be accomplished in a number of ways. One is to store in perforated plastic bags (like the ones apples and oranges come in), or they may be double-wrapped in craft paper bags (the old-fashioned paper grocery bags). They may also be stored in high (near 100%) humidity and periodically sprayed with water, but make sure you let the water drain away and don’t let chestnuts stand in water for any length of time.
Allow Chestnuts to Breathe—Chestnuts are living things, and they “breathe” oxygen and give off carbon dioxide. If you try to store them in an air-tight container, chestnuts will suffocate, and then spoil.
Curing Chestnuts—All chestnuts need to be cured before consumption for them to taste their best. When fresh off the tree, chestnuts will have a fairly bland flavor. To develop their rich, sweet flavor, chestnuts must be cured first. This is simple and easy (though is takes some time).
Place chestnuts in a shallow bowl, tray, or other container, and expose them to air at room temperature. Avoid direct sunlight, heat, or forced air. Do not pile chestnuts more than two deep. Leave them this way for 3 days to 2 weeks, depending on nut size. Larger nuts take longer to cure. Our “Large” size need about a week to cure.
At full moisture, a chestnut will be rigid, almost hard (like a fresh carrot). As chestnuts lose moisture (dry out), starches are naturally converted to sugars, and they develop their rich, sweet taste for which they are famous. The kernel will shrink away from the shell and become somewhat soft and spongy (much like a carrot that has been left sitting out for several days).
To Test for proper curing, squeeze the chestnut between thumb and forefinger. If it is still rigid, the chestnuts need to cure some more. If you can feel some space between kernel and shell, open the nut. The kernel should be soft and spongy. If so, curing is complete. Taste and enjoy!