Does Flour Go Bad?

With plans for bunches of loaves of bread, some cookies to snack on, and a tomato pie, flour is a pantry staple in Southern kitchens. But when busy weeks (OK, months) get between you and those baking plans, your bag of flour is left sealed up in the pantry for longer than you would like. As a shelf-stable food, flour seems like one of those ingredients that could last forever, but flour does indeed expire.

Here's how to know if flour has gone bad—plus, what to do if your flour is expired and it's all you have on hand.

Does Flour Expire?

Flour does have "expiration" dates, but that doesn't necessarily mean you can't use the flour. There are a few things to check before you toss that bag of expired flour.

All flour sacks have a "best by" or "best if used by" date printed on their packaging. This is the manufacturer's suggested date to ensure the flour's best quality.

Do not confuse this with a "best sold by" date, which serves as guidance for the grocery store on when to remove the flour from the shelves. There is some wiggle room as flour generally remains good for up to six months past that date, depending on your storage system.

What may determine if flour is "expired" has less to do with the dates on the bag and more to do with the flour's ingredients. The natural oils in flour are susceptible to spoiling. Basically, the more fat the flour contains, the quicker it will expire. Additional ingredients like salt or baking powder do not affect spoilage, but they will lose potency as they age.

How Long Do Different Types of Flour Last?

The natural fat content in the grain, nut, or starch used to make the flour drives the expiration period of the flour. Therefore, flours will last different lengths of time based on what is used to make them.

Refined flours

The rule of thumb here is the more protein, the lower the shelf life. For low-protein types of flour, like all-purpose or cake flour, you have about a year from the date of purchase to use it. For higher protein varieties, like bread flour, the clock runs out quicker; you'll get about nine months.

Self-rising flour

This white, refined flour has the addition of leavening agents like baking powder which doesn’t cause it to go rancid but will lose potency and no longer be effective for baking after four to six months.

Whole-wheat and whole-grain flours

This category includes white as well as darker whole wheats, pumpernickel, rye, oat, and other types of whole grain flours. The key for these varieties is to store them in airtight containers away from light and moisture. If stored properly, they usually have about a one-year shelf life.

Starch-based flours

These flours don’t include wheat. Examples are potato, tapioca, and cornstarch. If they are refined and white, the shelf life is similar to all-purpose, approximately one year.

Nut flours

Almost any nut is a candidate for flour, but they still follow a nut’s shelf life. Once ground into flour, the natural oils distribute and are open to environmental factors that cause spoiling quicker than when the body of the nut protected them. Depending on the oil content, this could mean it will go bad in as little as three to six months. The Whole Grains Council offers specific guidance.

Gluten-free flours

These types of flours often include nuts to bulk up the mix, which means a shorter lifespan for peak quality, anywhere from two to 12 months, depending on storage and type.

How Can You Tell if Flour Is Bad?

Remember that "best used by" date printed on the package? Though important as a guideline, you should physically inspect the flour before tossing.

If you open the bag and it smells bad, it probably is. This is a sign that the fat in the flour has oxidized, usually resulting in a musty or sour smell.

Physically, the flour could be clumpy or beginning to yellow, indicating moisture has gotten to it.

Then of course, if you see pests like weevils, ditch the bag. Be careful about throwing in your regular kitchen trash or compost bin—you don’t want any critters escaping to infest something else in the pantry. 

Can You Use Expired Flour?

According to the U.S. Department of Agriculture (USDA), expiration dates do not constitute safety. Expired flour can be safe to use if the flour is still good. However, flour does go bad, which you can determine from smell and appearance.

If the quality has deteriorated and you use it, whatever you make will mirror those deficiencies. If it is rancid, your finished dish will have that sour scent and flavor, and maybe even cause gastrointestinal issues. If it has gotten too much air or moisture, the texture of your baked goods will be crumbly. If the leaveners like baking powder are past their prime, the bake will fall flat.

While using flour past its date is fine if there are no signs of deterioration and it has been stored properly, it won’t yield the same results as fresh flour.

How To Store Flour for Maximum Life

Storage is probably the most important consideration when figuring out the longevity of flour.

According to the USDA, flour is considered shelf-stable and can be safely stored at room temperature. You probably have your bag clipped in the pantry, but you should have transferred that bag to a sealed, airtight container and then stored that container in a cool, dry, dark place.

It’s also great practice to label the “best by” date on the container so you know where you stand when it is a while between uses.

Refrigeration is a great tool to extend the shelf life of a bag of flour. Make sure it is sealed for protection against air or moisture, and then store it in the refrigerator for approximately a year or the freezer for two years (yes, even whole wheat).

Unfortunately, nut and gluten-free flour still expire earlier, but refrigeration does help their shelf life. This path is a great option if you are an occasional baker or like to incorporate different types of flour into your projects. Just be sure to bring your flour to room temperature before using, especially when baking bread, to prevent lumpiness.