You’d be hard-pressed to find an ingredient that is more versatile in the kitchen than olive oil, but what how long does olive oil last before it turns from liquid gold to rancid?
20 years ago, archaeologists in the prehistoric settlement of Castelleccio, Sicily, found an ancient dump.
But this wasn’t just any garbage pit. It was a pile of ancient Roman clay olive oil containers. The trace of olive oil recovered on it, found to date from 2,000 BC, is the oldest in the world.
“Contrary to wine, which responds well to ageing, olive oil is best used when it’s young and fresh and at the height of its nutritional value,” said Astrid Liakou, an expert certified olive oil sommelier.
You might not have ancient storage containers full of olive oil — just an old jug of oil that you were gifted once, and that has lived in the back of your cabinet seemingly since the Roman era. But how can you tell if it’s still edible?
How Long Does Olive Oil Last?
On average, the typical bottle of olive oil you purchased from your local supermarket or gourmet store will last from two to four years. But olive oils are all unique, and their shelf lives vary depending on their quality, where and when they were harvested, how they’re pressed, and how they’re stored.
Check the Harvest and “Best By” Dates
Your best bet in determining the lifespan of that special bottle of olive oil you purchased on vacation in Barcelona last year (or, admit it, got on sale at the grocery store or online) is evaluating the harvest and expiration dates. Most reputable brands will include these dates somewhere on the packaging.
The harvest date is a better indicator than the bottling date, which some producers also include, because olives are only picked to make oil once a year, and that might be some time before the oil is actually bottled and distributed. Olives are usually harvested in the fall, so the freshest olive oil would have a harvest date from the most recent autumn.
Recommendations for how long a particular oil will stay fresh vary by manufacturer. Many producers will list a “best by” date around two years from the harvest date, but oils can begin to oxidize within a year of harvest. Bertoli’s estimate is more conservative, at 14-months. A good rule of thumb might be the Italian government’s guideline, which is 18 months from harvest.
While the harvest date is a great guideline, the best way to tell whether your oil has gone off is your own sense of smell and taste. Learning how and why olive oil goes bad — and training your palate to understand oil quality — can help you become a more discerning consumer, and a chef’s-kiss-worthy cook.
Learn a Little Chemistry
Olive oil goes bad thanks to the same chemicals that make it so healthy to begin with: antioxidants.
Antioxidants include components like vitamin E and polyphenols, and they help us by scavenging free radicals. That means they process oxygen molecules that have broken down into single atoms, which, if unchecked, can cause damage to cells.
While they can help us stay healthy (and hopefully, live longer), antioxidants themselves don’t live forever. After a period of time, they’ll begin to oxidize, or break down. This happens more rapidly when they’re exposed to light and air, which is why organizations like the California Olive Oil Council recommend choosing oils that are packaged in dark glass or tin.
Trust Your Taste
While harvest and best-by dates are the most obvious metric, the most surefire technique to determine whether your olive oil has gone bad is also the most fun: Taste it!
“Good olive oil should taste and smell fresh, like a freshly picked still green olive rubbed between your hands or similar to a green almond picked fresh from the tree,” Liakou said.
If you, like most people who don’t live on olive-producing regions, have never smelled a fresh olive, Liakou recommends looking for “a fresh, slightly green scent of a newly sprouted twig on an apple tree in the spring.”
Quality olive oils may also have bitter or spicy notes, leaving a prickle at the back of your throat. This isn’t an indication that the oil has gone bad — it’s just a natural flavor variation.
Color also isn’t necessarily an indication of freshness or quality. Variation in color, from golden to greenish, is natural.
How Do You Know If Olive Oil Has Gone Bad?
Olive oil that has gone bad will taste — you guessed it — bad. According to Liakou, if your bottle of oil smells like the black olives left out too long on an appetizer table last Thanksgiving, you’ve likely got a rancid bottle.
This taste is different, by the way, from a spicy, tingly or slightly sharp oil. A high-quality oil can sizzle on the palate, like a dash of pepper on the back of your throat. In contrast, olive oil that has gone rancid will carry notes more reminiscent of french fries kept too long in the deep fryer.
Your best bet in figuring out when your olive oil has gone bad is knowing what it tastes like when it’s good. So cook with that gourmet bottle as soon as you receive it at your housewarming party, or head to a fancy olive oil store and help yourself to free samples: It’s research.
Is It Okay To Use Expired Olive Oil?
Technically, yes, you can use expired olive oil and it shouldn’t make you sick or cause serious side effects. However, rancid olive oil will lack in nutritional value compared to a freshly acquired bottle. It will also cause whatever dish you’re making to have a weird and unappealing taste, so if it’s flavor you’re looking for, it’s probably best not to use olive oil that has gone bad.
How to Store Olive Oil
Olive oil should be stored in an airtight container that can shield it from sunlight, such as a dark glass or pottery.
“The archenemies of olive oil are exposure to air, light, too high or low temperatures and strong odors that it can pick up,” Liakou said.
It’s also important to keep olive oils away from heat sources like stoves or ovens. Because olive oil generally goes rancid after two years, buy accordingly.
If you have an Italian grandmother or come from a Mediterranean country, you might have grown up with vats of olive oil bought either directly from the grower or from the grocery store, kept in a cabinet and then regularly transferred to a container for liberal use in cooking.
If you foresee using much less oil than a Mediterranean granny, however, it’s best to buy in smaller quantities so your haul doesn’t go bad before you get a chance to eat it.
“If you are unsure about whether you can use up your bottle in say 2-3 months, opt for buying a smaller one to start with and move to larger bottles when you increase your consumption,” said Liakou.
How Can I Pick The Best Quality Olive Oil?
Another way to extend the life of your oil, and make sure you’re having the best taste experience, is to choose better-quality oils in the first place. While price isn’t always indicative of quality, top-quality oil is more expensive than olive oils adulterated with other kinds of vegetable oils, like canola oil, and a 750 mL bottle of very high quality oil can cost upwards of $50.
You can easily access more affordable extra virgin oils at your local grocery store or online, where three-liter tins can go for $20 or $30. But price isn’t the only indication, or even the primary indication, of an oil’s quality. Instead, you can look for packaging indications that an oil is fresh and of high quality.
Production Conditions Matter
The quality of the resulting oil depends on the conditions of the olives as they are picked, stored and transported. According to Liakou, good oil should be pressed from slightly unripe olives within a day of harvest. If the olives are bruised or not very fresh, the resulting oil will oxidize, leading to a shorter shelf life and a rancid smell and taste.
Grocery store conditions matter, too. Olive oil should be stored in an opaque container to prevent light from oxidizing the oil, so look out for a dark glass or tin container.
Look For an ‘Extra Virgin’ Label
Extra virgin certification, the highest quality grade an oil can get, indicates that high standards of production have been met. According to the California Olive Oil Council, extra virgin labeling means that the oil has been tested in a lab and found not to have chemical additives or to have undergone chemical reactions that would affect smell and taste.
Besides the chemical testing, oils are certified extra virgin through the most sensitive instrument: a panel of olive oil sommeliers who taste the product to make sure it’s of superior quality, with no taste or odor defects.
Professional and governmental bodies — from the European Union’s olive oil marketing standards and Protected Geographical Indication, to the California Olive Oil Council’s Seal Certification Program — offer further assurance to consumers.
Beware of Olive Oil Fraud
There have been numerous recent reports of olive oil adulteration, from adulterated oil being sold under the “extra virgin” label, to the mafia profiting from olive oil fraud. In fact, olive oil fraud is as old as civilization itself: The world’s first written mention of olive oil, on a 24th century BC Syrian tablet, concerns detection of fraudulent olive oil.
Nonetheless, some research suggests the problem may not be as widespread as alarmists might have you think. In a 2015 study, the FDA found that only three of 88 tested olive oils had been adulterated. Still, researchers are hard at work developing affordable, convenient ways to test olive oil for purity, including near-infrared spectroscopy that can test the purity of large quantities of oil in a relatively short amount of time.
The Final Taste Test: Educate Your Palate
The best way to tell whether your olive oil is of good quality, or whether it’s gone rancid, isn’t fancy machines or even the labeling on the bottle: It’s your own sense of taste and smell. While the idea of “educating your palate” may sound unattainably posh, it’s actually the most accessible and fun way to learn about food — through eating it.
Try free samples at upscale olive oil stores, hint to your loved ones that a fancier-than-usual bottle is exactly what you want for your next birthday, and sprinkle your cooking with as much of that good, golden stuff as you want. It’s healthy, delicious, and the more you eat it, the more educated you’ll be.
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