Here's How To Tell If Flour Has Gone Bad
Flour is likely a staple in your pantry, but it can be hard to know how long it stays fresh. Many flours are still good to use three to eight months after purchase, usually long after the expiration date listed on the package (via Healthline). However, the product's true shelf life will depend on several factors, including the type of flour and how it is stored.
White flour, for example, has a longer shelf life than whole wheat flour because of the manner in which it is processed. It is highly refined and stripped of bran and germ, meaning only starchy endosperm is left. Whole wheat flour, on the other hand, contains all three parts of the grain. Since bran and germ are high in perishable oils, it is more susceptible to spoilage.
How you store flour also matters. Flour is considered to be shelf stable, so it can be stored at room temperature. The best way to preserve its freshness is to keep in an air-tight container and store it in a cool, dry place. Flour that is stored in the refrigerator or freezer will last longer, up to one year or two years, respectively. If you go this route, make sure to store it in an air-tight container to prevent mold.
When it's time to toss your flour
Most packages of flour will have an expiration date, but these labels are not mandatory and don't indicate safety. Thus, your flour may still be good to use even after this date has passed. So how can you tell when your flour has gone off? The best way is to smell it. Flour has a neutral smell, so when you get a whiff of something that's stale, musty, or sour, it's time to throw it away.
When wheat flour is bad, it will change in color and texture (via Livestrong). Fresh wheat flour is light tan in color and has a smooth texture. When it's gone off, it will darken and turn crumbly. If you taste fresh whole wheat flour, it will be nutty, but when it's on its way out or has already gone bad, it has a sharp, moldy taste that won't be pleasant. Finally, if flour has come into contact with moisture, large clumps of mold may form. If this happens, toss the entire bag in the garbage immediately.