Although there's not much you can do if your flour has already gone bad or sprouted bugs, a few simple steps will help to prevent these maladies.
Proper Storage Steps
All you need are sturdy, food-grade plastic bags and food-grade containers with lids, your freezer, and a cool, dark spot.
- Put the container of flour in a strong, food-grade plastic bag. If the flour is packaged in paper, put the whole paper bag inside a food-grade plastic bag.
- Remove excess air from the bag and seal tightly.
- Freeze the flour for two days to kill off potential weevils or insect eggs in the flour.
- Remove from freezer after two days and sift the flour into a food-grade plastic container with a tight-fitting lid. Label the container with the expiration date or sell-by date.
- Keep in a cool, clean, dark place to prevent other insects from getting at the flour and to prevent sunlight and moisture exposure, or keep it in the fridge if you're unsure your cupboard is cool enough.
Bugs and Rancid Smells
The bugs found in flour and other grains are called weevils. If you find these bugs in your flour (any brownish surface on top of your flour is the eggs), chances are the eggs were there before you purchased it because female weevils lay them inside the grain kernel, and they hatch between one and five months later. If you're unsure, rub some of the brownish flour between your fingers and if you catch a minty odor, that's the bugs. You can also tightly pack some flour up to the rim of a glass and make a flat surface with the help of a knife. Leave the flour exposed to sunlight for a few hours. If the tight surface looks broken, that's the bugs' doing. Toss it.
Rancid smells happen because the fats in whole grain flours oxidize when exposed to air and moisture. Over time, inadequate storage will continue lowering the freshness of your flour, affect the result of your baking, and maybe even make you sick. If your flour already smells musty, it's time to toss it.
When in Doubt
Follow these guidelines when you're not sure if the flour you have at home is still good to use:
- Refined flours like pastry or self-rising flours keep fresh for up to two years but will smell sour when past their prime.
- Nut or seed flours like almond, flax, or hemp should preferably be stored in the freezer, and they can last up to a year. If they have a burnt or bitter taste, that means they're not good anymore.
- Whole-grain flours like wheat, spelt, or barley have just 3 to 6 months of shelf life, so keep them in the fridge and check the expiration date before using. If you catch a funny smell, then it's time to discard them.
Different Types of Flours
By keeping your flour properly stored you're securing its freshness. However, not all flours are made the same and not all keep fresh for the same amount of time. Keeping them in the fridge will give you extra months of use after the expiration date or the sell-by date, but do keep in mind that non-wheat flours like gluten-free and nut flours have different needs. So every time you open your bag of flour, regardless of what it's made of, sniff it for foul odors and check its texture to ensure that no bugs are present.