Lots of food is preserved in olive oil, so I wondered: can olive oil go off?
After some research I’ve found out that yes, olive oil can go off. Unopened olive oil lasts for about a year and a half. After you have opened a bottle of olive oil, use it within two months. After that, it can go rancid, oxidise and taste unpleasant.
Even worse, I just found out that some olive oils have already gone bad by the time you buy them – even if the bottle’s still sealed.
How do I know if my olive oil has gone off?
The best way is to taste it, if it isn’t flavoured or infused. It’s a sad fact that so many restaurants serve old oil (usually the stuff you’re given to dip bread in) that some people are used to the taste of older, less fresh oils and might not be able to tell the difference.
Rancid olive oil tastes “greasier” than normal and usually has a flavour like gone-off nuts or plasticine. It should taste fruity, grassy and sometimes floral, not fusty or dank. Fresh oil gives you that pleasant peppery “kick” at the back of your throat, whereas an older olive oil won’t.
If you don’t want to taste it, then the sniff test is another good way to tell if your olive oil has gone off. Older oil should smell of those same putty-like, fusty notes.
What makes olive oil go rancid?
There are a handful of things that can make olive oil (whether extra virgin or not) go bad:
- Time – if it’s older than two years (yes, even unopened) then it’s probably past its best. If you’ve bought or been given a nice bottle of quality extra virgin olive oil then forget delayed gratification or a special dinner. This is your excuse to use it! Olive oil is not like wine – it won’t improve with age.
- Exposure to light (particularly UV). This oxidises the compounds in the oil and makes it go off faster. You may have noticed that expensive olive oils come in very dark (usually green) bottles – it’s to stop the light getting in.
- Heat – too much of it will make the olive oil spoil faster and, like light exposure, causes the volatile compounds in the oil to react in undesirable ways, leading to an off-tasting oil.
- Oxygen – most oils oxidise before they go rancid. In other words, exposure to the air (i.e. leaving olive oil uncovered or forgetting to put the cap back on) is bad for olive oil.
Will expired, old or rancid olive oil make me ill?
Gone-off olive oil won’t taste nice, but usually it won’t make you sick. Beware, however, of infused, flavoured or homemade oil products. These are ones such as garlic oil, herbal infused oils, and other similar olive oil products.
The oil itself isn’t the culprit, it’s the items in the oil infusion – botulism spores thrive in these sorts of conditions and can make you very ill indeed. Unless it’s straight olive oil with no additions or flavourings, it’s better to throw it away rather than even testing it to see if it’s gone bad.
How to store olive oil (and does olive oil go bad in the fridge?)
Since olive oil doesn’t do well in warm environments, you can store olive oil in the fridge quite happily. If you live in a cooler climate, like I do in the North of England, then this usually isn’t necessary. Make sure it’s in a cool cupboard away from the oven, toaster or other heat-emitting devices in your kitchen.
Fridge lights go off when you close the door, so the fridge is also a good place to make sure your olive oil is stored in a dark place. Again, it doesn’t have to be the fridge, just choose a cool, dark cupboard or shelf.
Olive oil doesn’t like humid places so if your kitchen is warm or stuffy, try to keep it somewhere else where it will remain cool, dark and dry.
You can freeze olive oil, but this will make it solidify, so usually it’s just best to keep it somewhere cold.
My olive oil is cloudy and/or has white spots. Has it gone off?
If your olive oil sets get thicker, go cloudy or have white solids in it, it usually means its been stored somewhere cold, like the refrigerator. Don’t worry, the cloudiness will disappear when the oil is brought back to room temperature. The quality isn’t affected, and you can use it as normal.
A myth still travels around the internet that such cloudiness or solidification means the olive oil is impure, and that you can rely on this as some sort of “olive oil impurity test”. It isn’t true. White solids are not signs of impurities or defects.
Unfiltered olive oil, which is perfectly good, often has white, waxy deposits or cloudiness in it at slightly higher temperatures. If you want to clarify it, just heat it up a little.
What to do with unused but still fresh olive oil
If you’ve served olive oil in a dipping dish or similar and have some leftover, don’t be tempted to pour the unused oil back into the bottle.
The oil in the dish will be more oxidised than the olive oil in the bottle, and you’ll also be inadvertently pouring tiny food particles (mmm, focaccia) back in there, which accelerates the deterioration of the whole bottle. Use it up within a day or two by mixing it into a salad dressing or cutting it with veg oil for frying (yes, you can fry with olive oil).
Alternative uses for old or rancid olive oil
Chucking old olive oil down the sink pains me, because I try not to waste food and attempt to re-use and recycle as much as I can. Some ideas for using rancid olive oil are:
- Condition your wooden chopping board with it. You don’t need to use a lot, so the board won’t smell rancid. Just use a half teaspoon and rub the wood with it after cleaning.
- Use it to oil creaking gates, squeaky hinges, or other small DIY jobs. You can also use it as a lubricant when sharpening kitchen knives.
- Season new pans and cookware with it. You usually need to use oil to season brand new cast iron, aluminium or steel cookware, particularly frying pans. Since the oil is unusable afterwards and must be thrown away, it’s a great use for old olive oil.
Expiry and harvest dates on olive oil bottles
- If it’s past its expiry date, even if you haven’t opened it… it’s probably not that nice to eat and you should find other uses for it, detailed later in this article.
- It won’t kill you if you do eat it, but you won’t benefit from most of its healthy properties (antioxidants in particular).
- Good quality extra virgin olive oil usually has a harvest date or year on the label. If you’re more than two years on from that date, it’s better to use it for something other than cooking.
5 hacks to ensure you buy fresh extra virgin olive oil
- Buy online. This is the best way to get fresh, excellent quality oil. There are loads of wonderful small producers all over the world selling their oils directly online. They list the harvest date, the methods, the people… sometimes even the single estate or grove the olives were grown on. You might be interested in this in-depth article I wrote on where to buy quality olive oil online.
- If you do buy in a shop or supermarket, ALWAYS check the harvest date on the back when buying in a shop – some oils are sitting on the shelf for so long, they’re already old when you buy them, even if they’re not past their “best before”. Sometimes the “best before” is artifcially long, too. No harvest date? Then you won’t know how old it is from the start, and is best avoided.
- Choose oils presented in an opaque tin or dark bottle. One of the giveaways of cheap olive oil is when it’s presented in a clear glass or plastic bottle, since this is a cheaper form of packaging. How long has that oil been sitting facing a fluorescent light or been blasted by the shop heating? It won’t have done it any good.
Similarly, have a root around and try buy a bottle that has been sitting in the dark and cooler places at the back of the shelf.
- Check the country of origin. If you buy online from a producer or good distributor, this is obvious and so not really a factor, but if you’re looking at physical bottles then scrutinise the label. Sometimes it’s hidden in small print. If it’s unclear, it may be a blend of different estates and ages, which is poorer quality.
Sometimes extra virgin olive oil on the label doesn’t reflect what’s in the bottle at all. This is a classic example of food fraud.
- Have different olive oils for different applications, so you use smaller bottles more often instead of one huge bottle that’s going to go off before you have a chance to use it all. I use single estate extra virgin for salads, dipping and some dressings.
More neutral-tasting non-extra virgin is better for mixing into recipes (cakes that call for oil, for example) or for marinades or sometimes, frying. Yes, I’ll say it again, you can fry with olive oil.
Overall, it’s worth buying quality in small quantities when it comes to olive oil. Stored properly, it will last for a long enough time for you to enjoy it and taste it how nature intended it to be – fresh, grassy, peppery, green and delicious!