You make your famously flaky piecrust only once a year, so you want to be sure the ingredients are at their peak. But when it comes to evaluating the freshness of flour and other dry baking ingredients, the proverbial sniff test doesn't cut it. Here's when to refresh your baking staples.
To prevent pests, replace white flour once a year if it has been stored in an airtight container in a cool, dry place. Whole-wheat and other whole-grain flours should be replaced every six months because they contain oils that can turn, says Mary Ellen Camire, a professor of food science and human nutrition at the University of Maine, in Orono. Whole-grain flour can become bitter after a few weeks. To prevent this, place it in the freezer in an airtight container immediately after bringing it home from the store, says P.J. Hamel, a test-kitchen baker for King Arthur Flour, in Norwich, Vermont, and replace it after six months.
You won't need to replace sugar for two years or longer, because "it's fairly indestructible," Camire says. Brown sugar, which can be softened by microwaving it for 15 seconds, is more perishable―replace it within a year. Keep both in airtight, moistureproof containers.
Replace baking powder by the use-by date printed on the can. Baking soda should be replaced within a year if it's opened, two if unopened. Both react with moisture and become less stable over time, so store them in a cool, dry place―not the refrigerator. If you use these ingredients when they're old, your cookies won't rise properly or have the right texture, says Hamel. And don't use the box of baking soda that has been in the refrigerator absorbing odors; it can affect the taste of the foods you bake.