Does Vegetable Oil Expire?

For many people, vegetable oil is a saving grace. It plays an extremely useful part in the cooking process, as it prevents foods from sticking to pans and helps them cook a little faster. Frying certain foods in vegetable oil, such as chicken, also gives them a crispy coating, adding to their deliciousness (via Green Matters).

In addition to making pans nonstick and giving foods a crispier crust, many types of vegetable oil are relatively healthy, per Healthline. For example, olive oil and avocado oil contain antioxidants, which assist with inflammation; sesame oil may offer protection against nervous system disorders like Parkinson's; and safflower oil potentially helps with blood sugar management. With all of these health benefits, it's no wonder that vegetable oil is so widely used in various styles of cooking. However, if you're a frequent user of vegetable oil, you may be wondering: does this useful, healthy ingredient ever expire?

Though vegetable oil is a pantry staple with a decent shelf life, it does eventually expire. According to Insider, unopened vegetable oil that is kept in a dry and cool area can last for about two years. However, opened vegetable oil has a shorter shelf life, lasting from about two or three months up to a year after opening, depending on the quality of the oil.

Expired vegetable oil can make your dish taste rather unpleasant, so it is very important that you know how to spot a rancid oil. But don't worry: there is a simple way to determine if vegetable oil is spoiled. All you need to do is pour some of the oil onto a spoon and smell it, per Cook's Illustrated. Since vegetable oil doesn't have a very strong aroma, if you notice a pungent, sour smell, or simply a different type of aroma, such as that of metal, you can safely say that the oil is expired. If it's an unrefined oil you're unsure of, like extra virgin olive oil, you may need to taste a tiny amount, pulling it through your mouth to see if you notice any flavors that seem off. 

It's not recommended to consume expired vegetable oil. As mentioned, rancid vegetable oil can make your dish taste sour, but it can also negatively impact your health. According to LiveStrong, there are two different types of rancidity that vegetable oil can experience: hydrolytic and oxidative rancidity. Hydrolytic rancidity only results in the oil smelling and tasting unpleasant, but oxidative rancidity produces compounds called oxygenated aldehydes, which are harmful to health. So, if a bottle of opened vegetable oil has been sitting in your pantry for more than three months, it's probably best if you just toss it.

However, even though it's not recommended to consume expired vegetable oil, you don't have to let this substance go to waste. Emergency Essentials reports that there are several useful things you can use rancid vegetable oil for, from removing rust from cast-iron objects to protecting yourself from mosquitoes in the great outdoors. These additional uses could be a huge bonus if you ascribe to a frugal or sustainable mindset.