Even when stored in an airtight container in a dark cupboard, used frying oil can taste fishy and stale after more than a month. Is there a better way to store it for re-use?
A cool dark cupboard is fine for the short term, since exposure to air and light hastens oil’s rate of oxidative rancidification and the creation of off-flavors and odors. But for long-term storage (beyond one month), the cooler the storage temperature the better. We fried chicken in vegetable oil and then divided the oil (strained first) among three containers and stored them in various locations: in a cool, dark cupboard; in the refrigerator; and in the freezer. Two months later, we sautéed chunks of white bread in each sample and took a taste. Sure enough, the oil from the cupboard had turned fishy and unpleasant and the refrigerated sample only somewhat less so, while the oil kept in the freezer tasted remarkably clean. Why? Though an absence of light is important, very cold temperatures are most effective at slowing oxidation and the production of peroxides, which are the source of rancid oil’s unpleasant taste and smell. That’s why storing oil in the super-cold, dark freezer is your best bet for keeping it fresh.