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Cooking oils are sourced from a number of different fruits (olive, avocado, coconut), vegetables (corn), legumes (peanut, soybean), nuts (walnut), and seeds (canola, sunflower). But the recipe for maximizing the freshness and natural flavors of these oils varies, just as it does in the natural world.
Exposure to oxygen, light or heat will subject oil to oxidation, eventually turning it rancid. So in general all oils used for cooking should be sealed tightly and stored away from any heat or sunlight, preferably in a dark pantry and away from appliances.
But while cooking oils can be stored at room temperature—assuming you don't make your home in the Sahara—some oils benefit from storage in the fridge. Many oils, once opened, actually have a longer shelf life when kept at lower temperatures. Here's a full rundown.
How to Store Cooking Oils
Canola and Corn Oil
These kitchen workhorses do just fine stored in a cool, dark cabinet, or you can refrigerate them if it takes more than a year to get through a bottle. Note that, when refrigerated, corn oil (and most other oils) will get cloudy. This is not harmful, and the cloudiness will disappear when the oil warms to room temperature.
Olive oil is renowned for its flavor and health benefits, and many of us use enough these days to justify buying it in bulk. But that can leave your supply sitting around for some months. Since the optimal temperature for olive oil is 57 degrees, a temperature not commonly found in most kitchens, storage is worth careful consideration.
In the past, virgin and extra virgin olive oil was sold in tin cans. Some still is, and with good reason. Olive oil is easily damaged by light; exposing it to heat or oxygen causes the nutrients to oxidize, and can cause a loss of flavor. As such, leaving olive oil out on the counter or a table, especially if the bottle gets direct sunlight, is not the way to keep it for more than a few days. Storing it on or near a stove—convenient as that may be—is another surefire way to turn olive oil rancid quickly.
If you’re buying a large bottle or tin, consider placing it in the coolest, darkest place in your home and using a smaller glass bottle in the kitchen (a supply that'll last you a week or two). It’s not necessary to store virgin olive oil in the fridge, but if you use it infrequently, that may extend its life a bit.
Refined or “pure” olive oil—the less tasty, less nutritious cousin to virgin olive oil—is less sensitive to heat and light, and has a longer shelf life.
One of the sturdiest cooking oils, peanut oil can be kept for as long as two years if stored tightly capped and away from heat and light. Keeping peanut oil in the fridge may extend shelf life even further, but be aware that it will solidify and become cloudy—something to plan for when you’re preparing a quick stir-fry. It will soften and clear after 30 minutes or so at room temperature.
A relatively recent re-addition to the American diet, coconut oil was used for years for movie theater popcorn, but in the 1990s got a bad rap for its high levels of saturated fat. Although scientific data is only slowly developing, the mainstream health community is starting to examine coconut oil for its nutritional qualities and possible benefits in combatting heart disease, arthritis, weight gain, and Alzheimer’s disease.
Like peanut oil, coconut oil is very stable and (when kept at room temperature) has a shelf life of two years or more. That's because it doesn’t break down when confronted with heat or light, like most other cooking oils. But because coconut oil only becomes liquid at 76 degrees Fahrenheit, it will solidify in most indoor environments. You may often find yourself scooping it, rather than pouring it.
Avocado, grapeseed, hazelnut, sesame, truffle, and walnut are among the oils that are especially prone to going rancid, especially if exposed to too much light or heat.
Walnut oil, in particular, is very susceptible to oxidation. Safflower and sunflower oils can also go rancid easily. For these and other delicate oils, refrigerating after opening is recommended. Kept cold, these oils will remain viable for six months or more.