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.