A NUMBER OF YEARS AGO, I went to the supermarket and bought an overflowing armful of cereal boxes and cookie packages. I’d started writing about the food industry for the New York Times not long before, and I’d decided to test whether those expiration dates printed on packages actually meant anything. I’d always wondered what happened to food after the expiration dates passed. Would the cookies turn green or taste like old shoes? Would bugs crawl out of the cereal? I tucked...