If you've gone to all the trouble of harvesting, removing the husk, curing, and cracking open your black walnuts, then you'll definitely want to preserve black walnut fruit properly to keep it from molding or going rancid. Luckily, the black walnut fruit is easy to store for later use no matter if you want to keep it at room temperature, or store in it the fridge or freezer. With a good harvest of well-preserved black walnuts, you can enjoy cooking with them for years.
Fill as many plastic bags as you have walnuts for. Depending on how quickly you'll use them and how many you have, gallon or quart sized bags will work.
Place a bag or two into your refrigerator on a shelf, not the door where temperatures can fluctuate, and store for up to nine months.
Store any longer term or excess bags of walnuts in the freezer. Once in the freezer, these walnuts can keep for up to two years and will thaw quickly if taken out just before cooking.
Prepare any nuts for storage at room temperature by baking them on a cookie sheet for 10 to 15 minutes at 215 degrees F. After they are baked you can keep the cooled walnuts in a jar or plastic container in a cabinet for two to three weeks.