Expensive isn’t always better: A moderately priced olive or canola oil from your supermarket may work perfectly well for sweating onions or sautéing meat, chicken or fish. But dishes where the oil’s flavor really shines through―like salads, pesto, bruschetta or vegetables―are where you’ll want to invest in a special extra-virgin olive oil or rich nut oil.
Do your homework: Not all brands are created equal. So where do you start? “The most important thing is to buy oil that’s been recommended to you by someone who knows something about oil, that you’ve tasted or that the storekeeper suggests for what you’re planning to cook,” says grocer and wine merchant Darrell Corti, president of Corti Brothers in Sacramento, CA. “Just like buying wine, you want to buy from a reputable merchant who knows his stock.”
Sometimes it makes sense to splurge: There’s a reason certain oils cost more than others. Olive and nut oils are expensive because their “fruit” is more expensive to grow and they are more labor intensive to produce than oils like canola, corn or soybean.
Store it right: Light, water, heat, and air are all enemies of oil, causing it to turn rancid. Storing cooking oils in a cool, dark place (such as your pantry or cupboard) with the top tightly screwed on can prolong their shelf life. Some oils require even greater precautions. Fragile olive and nut oils are highly prone to oxidation, causing them to become rancid easily. So they have a shorter life than other vegetable oils. Because olive oil thickens when refrigerated, it’s best stored at room temperature where, once opened, it will last for at least six months before it starts to deteriorate. Nut oils can start to become rancid in as little as six weeks after opening. You can prolong their shelf life (as well as that of peanut and sesame oils) by storing them in the refrigerator. Refrigerated nut oils will stay fresh for up to three months, while peanut and sesame oil will remain fresh for six months after they’ve been opened. Just be sure to bring them to room temperature before using.
Think small: Oils like corn, canola and soybean can last for more than a year once you’ve opened them, so it makes sense to buy them in large containers which are often less expensive. But just the opposite is true for more fragile nut, peanut, sesame and olive oils. Buying only the amount you’ll use within three to six months ensures that they’ll always taste fresh. Plus, you won’t waste money by throwing out oil that’s past its peak.
The right container can help: Clear glass bottles expose oils to harmful ultraviolet rays. While this isn’t as much of a concern for vegetable oils, which are more stable because they have been refined, exposure to light is a potential threat to unrefined olive and nut oils. Look for unrefined oils sold in metal tins or dark green or black glass bottles. This ensures that the oil has been protected from light from the time it was bottled until the time you bring it home to your kitchen.
Don’t be afraid to bring it back: Even if you pay up for a top-notch oil, there’s no guarantee it will in peak condition by the time you open it. “If the bottle sat on the dock for four days in 92 degree weather, that oil isn’t going to be good no matter how high the original quality was,” says Ari Weinzweig, co-founder of Zingerman’s in Ann Arbor, Michigan. If you open a bottle that’s gone bad, simply return it to the store where you bought it for a refund or an exchange.