The age of the oil is important. For many vegetable oils, it’s not possible to find out when they were made. But when it comes to buying olive oil, you can often find the harvest date printed on the label of high-end oils and some supermarket olive oils such as our winners, which are made by Bertolli and California Olive Ranch. Check this date to ensure that you’re securing the freshest bottle possible. Alternatively, some labels cite an expiration date, which producers typically calculate as 18 months from harvesting.
Monitor How Long You’ve Had the Oil
Unopened olive oil can go rancid one year after the harvest date. Once opened, olive oil has a shelf life of about three months. Vegetable, canola, corn, and peanut oils have longer shelf lives; they should be replaced six months after opening.
Buy Only What You’ll Use
Regardless of the type of oil, don’t buy in bulk unless you plan to use all that oil within its shelf life.
Keep Oil in a Cool, Dark Place
To maximize shelf life, move oil containers off your countertop and away from the stove, as heat and sunlight can accelerate the oxidation process. It’s better to keep oil in a cool, dark pantry or cupboard. A dark bottle can also help impede oxidation, so consider buying products that come in one. For the longest shelf life, Eric Decker, a professor in the Department of Food Science at the University of Massachusetts Amherst, recommends storing all your oil in the refrigerator, where cold temperatures will really slow down oxidation. The refrigerator is definitely our preferred storage location for nut and seed oils such as sesame and walnut oil; once refrigerated, they’ll keep for about six months after opening. If you choose this method for other oils, however, be aware that they may solidify in the refrigerator and must be warmed gently before use.