Yes, Your Olive Oil Could Be Expired. Here’s How To Find Out.

Be honest — how long has that bottle of olive oil been sitting on your counter? If it’s been sitting out on your counter and constantly exposed to the sun, we hate to break it to you…but you’re probably cooking with expired olive oil.

Not what you were expecting, was it? Well, it’s true. According to olive oil consultant Alexandra Kicenik Devarenne, director of Extra Virgin Alliance, olive oil can easily go rancid if you’re not storing and taking care of it properly…or if you’re not cooking with it enough.

But how do you know when the olive oil truly has gone rancid? We asked olive oil experts to share their key tricks for pinpointing expired olive oil, and how to take care of your bottle once you bring it home.

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What causes olive oil to go rancid?

Those clear olive oil dispensers may make your cooking space look aesthetically pleasing, but in reality, they are actually causing your olive oil to go rancid rather quickly. That’s because olive oil rancidity is due to oxidation; when olive oil is exposed to oxygen and light, it will expire faster.

“The oxidation of the unsaturated fatty acids in olive oil results in rancidity,” says Devarenne. “All olive oil will become rancid eventually, but olive oils oxidize at different rates depending on many variables,” such as the presence of natural antioxidants and vitamin E, typically elevated in extra virgin olive oil.

Even if the spout of your olive oil dispenser has a cover, there’s still air sneaking into your bottle that is quickening the process, causing your olive oil to go rancid before you know it. Light exposure and heat will also cause your olive oil to degrade and expire faster, and will even change the color of your oil. What was once a yellow or green color could easily switch to an orange-brownish yellow — one of the many telltale signs that you’ve been cooking with expired olive oil.

“The more it’s open, the more you use it, it actually oxidizes quicker,” says Mary Mori, California Olive Ranch‘s Vice President of Quality and R&D. “So at first it might not oxidize that fast, but the more what we call ‘head space’ that you give that bottle, the more it’s gonna oxidize because now there’s more oxygen you can’t avoid.”

What are the telltale signs that your olive oil has expired?

“We say that olive oil has become rancid when you can detect aromas and flavors that signal an advanced stage of oxidation,” says Devarenne. “Think old walnuts, crayons, window putty, and linseed oil. Also, the mouthfeel of olive oil deteriorates as it oxidizes, becoming unpleasantly greasy.”

Again, a change in color is a telltale sign that your olive oil has likely gone rancid. Expired olive oil will also have a flat waxy flavor compared to the usual fresh olive aroma that olive oil is supposed to have.

“An extra virgin olive oil should taste of fresh ripe and/or green olives,” says Devarenne. “Aromas and flavors cover a wide range: fresh-cut grass, tomato leaf, green or ripe banana, nutty, floral, spice, green apple, artichoke, etcetera.”

Related: 3 Healthy Ways to Bake with Olive Oil for Every Kind of Baker

How do you prevent your olive oil from going rancid?

Devarenne says there are four accelerators of oxidation to keep in mind when preventing your olive oil from expiring.

Keep your olive oil in a cool place.

“The pantry or another cool cupboard is good, and for long-term storage,” says Devarenne. “If you are gone for summer vacation, for example, the fridge is okay. Don’t refrigerate your oil all the time, though, because it solidifies and then needs to warm up before use. Very inconvenient, and also the repeated cooling and warming seem to accelerate the oil’s deterioration.”

Keep it tightly capped once opened.

“Use it up within a couple of months,” says Devarenne. “If you want to buy your olive oil in a larger volume container (often much more economical), you can gently decant it into smaller perfectly clean and dry bottles with no empty space at the top, cap them tightly and store them in a cool dark place. Let the oil slide down the side of the bottle so you don’t get lots of air bubbles mixed in.”

Store your olive oil in a dark place.

“UV light is extremely damaging to olive oil so keep it in the dark,” says Devarenne. “Buy in dark or coated glass, tins, or bag-in-box for light protection. If your oil is in a clear bottle, it should come in a box. And then always keep it in the cupboard or in the original box. My best light protection hack: Wrap clear bottles in aluminum foil for excellent light protection (okay, they look funky, but better to protect the oil!).”

Or, instead, buy your olive oil in an aluminum bottle. California Olive Ranch just released a line of aluminum bottles, sitting at a much cheaper price point compared to their usual glass bottle selection. These bottles are also smaller with only 355 milliliters, making it easy to use up your olive oil before it goes bad. Plus, the aluminum bottles are recyclable, light, and great for use in the summer months if you’re grilling or camping.

Use up your oil within two months.

“Olive oil is a perishable product, and freshness counts,” says Devarenne. “Over time the flavor profile of the oil will become milder and less vibrant. Unopened and properly stored, a well-made extra virgin olive oil will be good for two to three years after the harvest, but it’s at its best during that first year.”

Mori says olive oil in a glass or aluminum bottle should be used within one or two months so you can get the best quality and taste from that product.

“I always recommend [for consumers] to buy the size that makes sense for what you’re going to use within a month or less,” she says.

Read next: Coconut Oil , Avocado Oil, Olive Oil, Canola Oil — What You Need to Know