Does Flour Go Bad?

What Is the Shelf Life of Flour? 

Many factors influence flour's shelf life, or the length of time it lasts before beginning to spoil.

Most flours stay fresh 3–8 months at room temperature, usually long past their expiration date. However, the specific shelf life depends on the type of flour, its ingredients, and how you store it.

Types of Flour

Flour is often categorized by its level of processing, which affects its shelf life. The source ingredient, such as wheat or arrowroot, also has an impact.

For example, white all-purpose flour generally stays fresh longer than whole-wheat flour due to the ways in which each is processed.

White flour is highly refined, meaning that the grain is stripped of the bran and germ, leaving only the starchy endosperm. Conversely, whole-wheat flour contains all three parts of the grain — the bran, germ, and endosperm.

The bran and germ are rich in oils, making whole-wheat products more vulnerable to spoilage. This occurs when fats deteriorate upon exposure to light, moisture, or air, typically causing an undesirable taste and odor.

Because gluten-free alternatives like almond or coconut flour are often high in oil, they may also be more prone to rancidity than white flour.

Additionally, gluten-free all-purpose flour, which typically combines several nut- or root-based flours, may be more vulnerable to mold due to its high moisture content.

Storage Methods

What's more, the shelf life of flour depends on how you store it.

According to the United States Department of Agricultural (USDA), flour is considered shelf-stable. This means that it can be safely stored at room temperature.

Yet, it should be kept in an air-tight container in a cool, dry place to preserve its freshness. Refrigerating or freezing it may further increase its shelf life.

For example, all-purpose flour lasts 6–8 months on the shelf but up to 1 year if refrigerated and 2 years if frozen.

If you put your flour in the fridge, be sure to keep it away from moisture and water to prevent mold. This is best done by sealing it in an airtight container, such as a plastic bag or food bin.

Keep in mind that you should let refrigerated or frozen flour reach room temperature before using it. This will prevent lumping.

Summary

Flour's shelf life depends both on the type of flour and storage techniques you use. White flour lasts longer than whole-wheat and alternative varieties due to its lower fat content.

How to Tell If Flour Has Gone Bad

Most packaged flours have expiration dates — also called best-by dates — printed on the bag to indicate how long they'll stay fresh.

However, these labels aren't mandatory and don't denote safety. Thus, your flour may still be safe to eat even after the best-by date.

The best way to determine whether your flour is safe is to smell it. While fresh flour has a neutral odor, bad flour smells off — it can be stale, musty, or almost sour. It may also look discolored.

Additionally, if your flour has come into contact with water or moisture, large clumps of mold may appear. In this case, you should immediately discard the entire bag.

To prevent food waste, try creative ways to use your old flour when it's near or past its expiration date. Aside from baked goods like breads and cakes, it's also good for creating non-food items like playdough or homemade glue.

Summary

The best way to tell if flour has gone bad is to smell it. If it smells rancid or shows signs of mold, you should throw it out.

Risks of Using Expired Flour

When flour goes rancid, its molecular structure changes — which may produce harmful compounds.

However, no recent studies have revealed any detrimental effects of eating rancid flour. Although cooked foods made with it may taste unpleasant, they're unlikely to harm your health if eaten in small amounts.

On the other hand, moldy flour can be dangerous, as well as foul-tasting.

While not all molds are harmful, some can produce dangerous chemicals known as mycotoxins. These compounds can trigger symptoms like vomiting and diarrhea.

Mycotoxins are also linked to other serious illnesses, including cancer and liver disease, depending on the amount eaten and duration of exposure.

Thus, it's always best to throw out your flour if it smells bad or shows signs of mold.

Summary

Eating small amounts of rancid flour likely won't harm your health, but moldy flour may be incredibly dangerous due to its levels of compounds called mycotoxins.

The Bottom Line

Flour has a long shelf life but generally goes bad after 3–8 months.

White flour may last longest due to its lower fat content, while whole-wheat and gluten-free varieties spoil sooner. You can extend flour's shelf life by sealing it properly or refrigerating or freezing it.

Be sure to throw out your flour if it has any unpleasant odors, discoloration, or mold growth.