How do you know if olive oil is bad?

Quick answers

There are a few quick ways to tell if your olive oil has gone bad:

  • Check the expiration date – if it’s past the date, it’s likely bad
  • Smell the oil – rancid olive oil will smell off, musty, or stale
  • Look at the color – fresh olive oil is a bright green, old oil looks more yellow
  • Taste the oil – bad olive oil will taste bitter, metallic, or soapy

How to do a visual inspection

One of the easiest ways to check the quality of olive oil is to do a visual inspection. Here’s what to look for:

  • Clarity: Good quality extra virgin olive oil should be clear and free of any sediment or cloudiness. Cloudy or murky oil is a sign of possible contamination.
  • Color: Fresh olive oil ranges in color from green to greenish-yellow. Over time, the chlorophyll breaks down and the oil loses its vibrant color, turning more yellow. Old or bad olive oil will look more golden yellow.
  • Foam: When you gently swirl or pour the oil, it shouldn’t foam up too much. Excessive foaming can indicate old oil or adulteration.
  • Oil separation: Check that the oil hasn’t separated with a layer of clear oil at the top. Properly stored olive oil stays emulsified.
  • Particles: Look closely to make sure no particles or “bits” are floating around in the oil. This could be a sign of contamination.

So in summary, look for olive oil that is a vibrant green color, clear, doesn’t foam too much, stays emulsified, and has no sediment or particles. Cloudy, murky, golden yellow oil that foams a lot is past its prime.

Smell test

One of the best ways to determine if your olive oil has gone rancid is to smell it. Fresh, high-quality extra virgin olive oil has a fruity, aromatic scent. As it ages and oxidizes, the flavor profile changes.

Here’s what rancid or bad olive oil smells like:

  • Musty or moldy
  • Metallic
  • Like cardboard or crayons
  • Vinegary or like wine
  • Sour or fermented
  • Rotten or decomposing

If you pick up any of these types of smells, the olive oil is past its prime and should be discarded. Trust your nose – if it smells off, it’s gone bad.

Taste test

Along with smelling olive oil, doing a quick taste test can confirm whether the oil is still good or rancid. Here’s what to look out for when tasting:

  • Bitterness: Fresh olive oil should taste mildly bitter and pungent. Rancidity leads to an unpleasant, very bitter taste.
  • Metallic notes: Iron-like, coin-y metallic flavors are a sign the oil is oxidized and no longer good.
  • Soapy taste: If the oil makes your mouth feel soapy or dry, that’s an indication it’s gone bad.
  • Rancid flavor: You may notice a distinct rancid, decomposing, or rotten flavor. This means it should be thrown out.
  • Vinegary or winey: Vinegar-like, fermented, or wine-gone-bad flavors indicate spoilage.
  • Stale or cardboard flavors: Flat, bland, or cardboard-like tastes mean the oil is well past its prime.

High quality extra virgin olive oil should deliver a balance of fruitiness, bitterness, pepperiness, and other flavors. If it misses the mark, trust your taste buds.

Check the expiration date

Checking the printed expiration or best by date is one of the quickest ways to tell if your olive oil is still ok to use. The International Olive Oil Council recommends:

  • Extra virgin olive oil lasts up to 18 months past harvest date if stored properly.
  • Virgin olive oil lasts up to 18 months past harvest date if stored properly.
  • Refined olive oil lasts up to 18 months past the bottling date.

So check your bottle for the harvest date or bottling date and don’t use olive oil more than 18 months past that. The expiration date factors in the type of olive oil and time for deterioration. If you’re past the printed date, it’s time to replace the oil.

Check for oil separation

You can also visually inspect the bottle to check if the oil has separated. Look to see if there is a layer of clear or light colored oil along the top.

Fresh olive oil should stay emulsified and maintain the same consistency throughout the bottle. Separation happens when the oil starts deteriorating and is a tell-tale sign that the olive oil has gone bad.

How to store olive oil properly

To get the most shelf life out of your olive oil, proper storage is key. Here are some olive oil storage tips:

  • Keep olive oil in a cool, dark place around 60-70°F.
  • Avoid storage spots that experience temperature fluctuations.
  • Light accelerates oil deterioration, so store in an opaque container or dark area.
  • Refrigerating olive oil can cause clouding, shorten shelf life, and negatively impact flavor.
  • Store olive oil away from heat sources like stoves or dishwashers.
  • Keep the lid tightly sealed to limit exposure to oxygen.
  • Don’t reuse olive oil bottles – buy only what you’ll use in a few months.
  • Check the “best by” date and use within that timeframe.

Following these guidelines helps prevent olive oil from going rancid prematurely.

What causes olive oil to go bad?

There are a few main causes of olive oil spoilage:

  • Age: Oil deteriorates over time, gradually losing quality and developing rancid flavors.
  • Heat: Exposure to heat and warm storage temperatures accelerates oxidation.
  • Light: UV light causes the breakdown of olive oil’s compounds.
  • Oxygen: Oxygen leads to oxidation, especially if not properly sealed.
  • Free fatty acids: Hydrolysis of the oil produces free fatty acids and leads to rancidity.
  • Moisture: Any water getting into the oil provides an environment for food spoilage organisms.
  • Metal exposure: Iron, copper and tin can catalyze oxidation reactions.

Proper olive oil storage limits exposure to these elements to maintain quality and prevent rancidity for as long as possible.

Health risks of rancid olive oil

It’s not just the unpleasant taste and smell that makes rancid olive oil unappealing – it can also be unhealthy. Here are some of the potential risks:

  • Contains free radicals that can damage cells and increase disease risk.
  • Loses healthy phenolic antioxidants that provide many benefits.
  • May irritate digestive system and cause upset stomach or intestinal discomfort.
  • Harmful oxidation products may be toxic to the liver and cells.
  • Potential contaminants like molds, bacteria, or chemical residues become more concentrated as oil deteriorates.

While more research is still needed, it’s recommended to avoid consuming oxidized, old olive oil. Fresh olive oil contains healthy fats and antioxidants, but over time these beneficial compounds break down into less desirable substances.

Cooking with bad olive oil

You’ll definitely want to avoid cooking with olive oil that has gone bad. Here’s why:

  • Low smoke point – The free fatty acids in spoiled olive oil have a very low smoke point, which means the oil can start burning and smoking at low temperatures.
  • Unpleasant flavors – Rancid flavors will come through clearly when cooking, ruining your final dish.
  • Harmful compounds – Thermal oxidation of bad olive oil produces aldehydes, peroxides and other potentially toxic compounds.
  • Higher levels of free radicals – Heating damaged olive oil ramps up free radical production.
  • Gastrointestinal irritation – Cooking with rancid olive oil can upset your stomach.

For all these reasons, it’s important to only cook with high quality, fresh olive oil.

How to tell if flavored olive oil is bad

Flavored olive oils – like garlic, chili, lemon, or herb infused – can also go bad over time. Here’s what to look out for:

  • Check best by date – use within 1 year of purchase.
  • Look for murkiness or sediment at the bottom.
  • Smell for rancid, sour, or strange off odors.
  • Taste for soapy, metallic, stale, or other “off” flavors.
  • Watch for separation with clear oil at the top.
  • Trust your senses – does it seem pleasant and palatable?

The added ingredients mean flavored olive oils have a shorter shelf life – around 1 year when properly stored. If anything seems amiss, don’t use it.

Can you restore bad olive oil?

Unfortunately once olive oil has gone rancid, there is no way to restore it to its original freshness and quality. The chemical damage can’t be reversed.

Attempting to filter or “clean” rancid olive oil won’t make it worth consuming – the unpleasant flavors and oxidation will still come through.

Likewise, mixing old olive oil with fresh oil won’t cover up the defects. It will still retain a rancid taste and smell.

The bottom line – if your olive oil smells or tastes off, it should be discarded. Don’t try to salvage or “fix” it. Time to buy a fresh bottle!

Signs olive oil has gone bad

Here’s a quick summary of the signs that indicate your olive oil is no longer fresh and has gone bad:

  • Expired best by or harvest date
  • Cloudy, murky appearance
  • Golden, yellow color instead of green
  • Foams excessively when swirled
  • Oil separation in the bottle
  • Strange particles, sediment, “bits”
  • Rancid, musty, “off” smell
  • Bitter, metallic, soapy taste

Trust your eyes, nose and taste buds. If olive oil fails the visual, smell or taste test, it’s time to say goodbye and get a fresh replacement.

Frequently Asked Questions

How long does olive oil last after opening?

In general, opened olive oil will stay good for 6-12 months if stored properly in a cool, dark place. Higher quality extra virgin olive oil has a longer shelf life of up to 2 years after opening. Check best by dates and look for signs of spoilage.

Does olive oil go bad if it’s cloudy?

Cloudiness does indicate that olive oil has gone bad. Properly stored olive oil should remain free of any sediment or haze. Cloudiness happens when the oil starts to oxidize andtiny particles form in the deteriorating oil.

Can you use rancid olive oil for non-cooking purposes?

It’s not recommended to use rancid olive oil even for non-culinary uses like as moisturizer or removing makeup. The oxidized oil may still clog pores, irritate skin, and contain harmful free radicals. Opt for using only high quality olive oil.

What happens if you consume rancid olive oil?

Consuming rancid olive oil can cause unpleasant digestive upset including nausea, vomiting, diarrhea, and stomach pains. The free radicals and oxidation products may also be toxic. It’s best to avoid ingesting oxidized, old olive oil.

Does microwaving olive oil make it go rancid?

Yes, microwaving can speed up the oxidation process and cause olive oil to go rancid faster. The microwave heating leads to the formation of harmful free radicals and compounds that quickly damage olive oil quality.

The bottom line

Checking olive oil for signs of rancidity using your eyes, nose, and taste buds is the best way to determine if it has spoiled. Look for changes in appearance, smell, and flavor. Olive oil is a delicate product that needs proper storage to maximize its shelf life. Following expiration dates and relying on your senses helps ensure you toss olive oil before it goes bad.

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