Shelled or unshelled, raw or roasted, pecans can last for months or even years if you store them properly. Keep them in the wrong conditions, however, and they'll go rancid quickly, spoiling their flavor or even making them unsafe to eat. The key to proper pecan storage is keeping the nuts away from the factors that cause spoiling.
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Preparing the Nuts
How you prepare your pecans will affect their shelf life. Whole pecans in their shells will last longer than shelled nuts. Cracked or chopped pecans will last an even shorter time than pecans with their shells removed; the more of the meat of the nut exposed to the air, the faster the pecan will go rancid. When a pecan goes rancid, its oil content turns sour, affecting its flavor.
Nothing makes pecans go rancid faster than heat; an increase of just over 10 degrees in temperature can cut the shelf life of pecans in half. This is why roasted or candied pecans tend not to last as long as raw nuts. To preserve pecans as long as possible, store them in a cool environment. Refrigeration is ideal; pecans stored below 40 degrees will stay fresh for a year or more.
Contact with air, moisture or odors can ruin the quality of a pecan quickly. Like many nuts, pecans absorb odors from other substances they come into contact with, while high moisture content hastens spoiling. To keep your pecans fresh, store them in an airtight container such as a heavy freezer bag or a resealable plastic tub.
Pecans in a freezer will last even longer than refrigerated pecans. Unshelled pecans kept at 32 degrees or below will last for up to four years. Thaw frozen pecans slowly by letting them warm to room temperature when you're ready to use them. This process, called tempering, will help the nuts keep their quality by protecting them from condensation that would otherwise form on the cold pecans.