By Noelle Carter, Los Angeles Times (MCT):
Basic flours (such as all-purpose, cake, pastry and bread flours) are generally more stable for storage than whole grain or alternative flours, which last longer if stored in the freezer.
Storing flour may not be something we tend to think about often in the kitchen, but it can stale or go rancid if not kept properly, potentially ruining a recipe. Here are some tips from the L.A. Times Test Kitchen:
Basic flours (including all-purpose, cake, pastry and bread flours) are generally more stable for storage than whole grain or alternative flours. Before grinding, the grains are stripped of the bran and germ, leaving only the endosperm to be processed. The stripping (and optional "bleaching," or oxidizing) gives the flour its white or creamy color. Store these flours in a sealable plastic bag or airtight container, labeled with the purchase date. Keep them at cool room temperature (no higher than 75 degrees); the flour should keep for up to a few months. You can also freeze the flour; simply bring it back to room temperature before using.
Whole grain and alternative flours (including whole wheat, barley, oat and rye) contain more of the grain, starch or nut, increasing the flavor, color and texture of the flour. The fat content also is higher because of the oil in the grain, which makes the flour less stable and prone to rancidity. Because these flours can go rancid quickly, check to see whether the packaging has a processing date before buying; many producers now date their flours for freshness. Store these flours in a sealable plastic bag or airtight container in the freezer; do not store at room temperature. Bring the flour to room temperature before using.
To check to see whether a flour has gone rancid, smell it. Rancid flour will have an "off" smell.