The best way to store flour isn't what you think

 Have you ever pulled a two-year-old bag of flour out of the cupboard and wondered if it was still good to use? As a recipe developer, I go through a bag of flour every couple of weeks, so I wondered how long does flour last and how the heck do I store it? Is there any way to know when it's gone bad? "I advise people to remember that flour is perishable — it's not salt, it's not sugar, and it's definitely not inert. Take care of it," says Martin Philip, an award-winning author, baker, and baking ambassador for the King Arthur Baking Company. Taking a closer look at different types of flour the grains themselves will help give us the answers.

Types of flour

All whole grain kernels are comprised of three parts: the bran, the endosperm, and the germ. The bran is the outer shell, the endosperm contains starch and protein, and the germ carries the genetic information of the grain and fat. That fat turns rancid over time, which is why some types of flour are best kept cold, while others are stable at room temperature.

White flour

White flour including all-purpose flour, pastry flour, bread flour, and cake flour use only the endosperm of the wheat kernel — which has no oils in it — and don't require cold storage like other types of flour such as whole wheat or rye. Frank Tegetoff, a research and development specialist from the King Arthur Baking Company, recommends transferring the flour from its original paper bag to an airtight container, which will help keep out moisture and bugs. Whether your container is glass or plastic is up to you — just make sure the lid is closed tightly. Store the container in a cool, dry, and dark spot like a cupboard or pantry for up to one year.

Whole wheat flour

Whole wheat flour uses the entire wheat kernel — including the bran and the germ. The germ contains a little bit of fat which, when exposed to oxygen, can go rancid over time. "Freezing slows that process," said Philip. While whole wheat flour can last up to several months in the pantry or on the counter, its shelf life varies based on factors such as temperature, humidity, and its age. Storing whole wheat flour in an airtight container or sturdy resealable plastic bag (Philip recommends double bagging) in the freezer will ensure that your flour lasts through its expiration date.

Rye and other whole grain flours

The same storage rules also apply to rye and all other whole grain flours. Keep them in an airtight container in the freezer. And label them clearly, especially if you're storing more than one type of flour.

Gluten-free flours

Gluten free flours can be subdivided into white and whole grain types.

White gluten-free flours include white rice flour, tapioca flour, and potato flour. These flours are made up almost entirely of starch and contain no fats. If kept relatively cool and dry, these flours have an almost indefinite shelf life. Store these at room temperature in airtight containers.

Whole grain gluten-free flours include brown rice flour, sorghum flour, amaranth flour, and oat flours. These should be stored like other whole grain flours — in airtight containers in the freezer, where they will last for at least one year. Like all other whole grains, these contain fat that can go rancid over time at room temperature.