Olive oil, a staple in many kitchens around the world, undergoes changes when exposed to air. Understanding these changes and how to prevent olive oil from spoiling helps consumers make the most of this healthy fat.
Why Does Olive Oil Spoil?
Olive oil is extracted from olives, the fruit of olive trees. While still inside the olive, the oil is protected from oxygen. Once extracted and exposed to air, olive oil slowly starts to oxidize and degrade in quality.
Oxygen causes oxidation, a chemical reaction between oxygen and other compounds. Oxidation leads to free radicals, which are highly reactive molecules that can damage cells. Antioxidants help prevent oxidation by neutralizing free radicals.
Olive oil contains antioxidants like polyphenols that protect the oil from oxidation. However, these antioxidants deplete over time when exposed to light, heat, and air, allowing oxidation to occur.
Signs of Spoiled Olive Oil
As olive oil oxidizes, you may notice some clear signs it has spoiled:
- Rancid smell – Olive oil will start to smell bad, with a rancid, greasy odor.
- Change in color – The oil will turn from green or golden to a yellow/brown shade.
- Smoke point changes – The oil may start to smoke at lower temperatures.
- Taste defects – Rancid, bitter, metallic, or muddy flavors develop.
These changes indicate the olive oil has degraded and should be discarded. Consuming rancid olive oil is not dangerous, but it will not provide the same flavor or nutritional benefits.
Factors That Accelerate Spoilage
Certain factors cause olive oil to oxidize and spoil faster when exposed to air:
- Light – UV light speeds up oxidation. Store olive oil in a cool, dark place.
- Heat – High temperatures hasten oxidation. Avoid cooking with olive oil on very high heat.
- Oxygen – More exposure to air means faster oxidation. Minimize oxygen by storing oil in full containers.
- Time – The longer olive oil sits after opening, the more oxidation occurs.
- Damaged antioxidants – Processing and refining olive oil reduces beneficial antioxidants.
- Polyunsaturated fats – Oils higher in polyunsaturated fats oxidize quicker.
Extra virgin olive oil resists rancidity better than refined varieties due to its higher percentage of antioxidant compounds. However, no olive oil lasts forever once exposed to air.
How Long Does Olive Oil Last?
How long opened olive oil lasts depends on storage conditions and the type of olive oil:
- Extra virgin olive oil – 6 months to 1 year
- Virgin olive oil – 9 months to 1 year
- Pure olive oil – 6 months
- Light olive oil – 6 months
General guidelines for maximizing shelf life are:
- Buy only as much as you will use within a few months
- Choose opaque bottles or tins to limit light exposure
- Store olive oil in a cool, dry place around 60-70°F
- Keep olive oil containers tightly sealed
- Limit oxygen exposure by keeping bottles full
- Use opened olive oil within 3-6 months
Storing Olive Oil Properly
To get the most shelf life out of your olive oil, proper storage is key. Here are some tips:
- Purchase smaller bottles you can use up quickly after opening.
- Choose dark colored glass or stainless steel containers that protect against light.
- Look for bottles that minimize air exposure with features like pumps, one-way valve spouts, or vacuum-sealed tins.
- Transfer oil to smaller bottles to limit oxygen exposure once opened.
- Refrigerate oil if you won’t use within 1-2 months. Cold helps slow oxidation.
- Freeze oil for long-term storage of up to 2 years.
- Use up cooking oils like olive oil within a couple months after opening.
- Save more delicate, expensive oils for finishing and dressings.
How to Tell if Your Olive Oil Has Gone Bad
Checking olive oil for signs of rancidity is easy. Here’s what to look and smell for:
- Appearance – Oil will look more yellow or gold, instead of greenish.
- Smell – Sniff the oil. Rancid oil smells foul, musty, like crayons, or rotten.
- Taste – Defective flavors include metallic, soapy, bitter, muddy, or greasy.
- Texture – Oil may become thicker and cloudier rather than clear.
- Smoke point – Heated oil will start smoking at a lower temperature.
If your olive oil fails the sight, scent, or taste test, it’s time to throw it out and begin fresh. Don’t compromise quality by trying to salvage spoiled oil.
Does Rancid Olive Oil Go Bad or Make You Sick?
Eating rancid olive oil does not pose any health risks. You may get minor stomach upset from the unpleasant flavors, but olive oil does not contain any harmful bacteria that can make you ill.
Rancidity is a natural process of oxidation as the oil breaks down. It does not mean the oil is contaminated or spoiled in a dangerous way – it has just degraded too far in quality to be enjoyable.
The main reason to avoid rancid olive oil is the loss of positive sensory qualities and nutrition. Healthy fats and beneficial plant compounds like polyphenols and antioxidants diminish.
Ways to Use Up Olive Oil Before It Goes Bad
If you have a bottle of olive oil you need to use up soon, here are some delicious ways to enjoy it before it oxidizes and goes rancid:
- Saute vegetables, fish, chicken, or other proteins
- Roast vegetables tossed in olive oil
- Make salad dressings and marinades
- Stir into soups, stews, pastas
- Use to oil pans for cooking
- Create olive oil-based herb infusions
- Make baked goods like cakes, breads, muffins
- Brush on meat, seafood, or vegetables before grilling
Extra virgin olive oil and other high quality varieties are best saved for uncooked uses like dressings. For cooking, use more refined, pure olive oils which have a higher smoke point and less delicate flavor.
Can You Reverse Rancidity in Olive Oil?
Unfortunately, once olive oil has gone rancid, there is no way to reverse the oxidation. The only option is to discard rancid oil and start fresh with a new bottle.
Be sure to smell and taste olive oil before using it if it has been stored for longer than 3-6 months. Look for signs it has spoiled before you cook with it or combine it into a recipe.
While you can’t reverse rancidity, you can take steps to better preserve olive oil and slow oxidation:
- Buy smaller bottles
- Limit light and oxygen exposure
- Keep olive oil in cool, dark storage
- Use up within a few months of opening
Healthiest Ways to Cook with Olive Oil
To get the most nutrition from your olive oil, use these healthy cooking methods:
- Cold use – Use extra virgin olive oil unheated in salad dressings, dips, and marinades.
- Low heat cooking – Saute over low to medium-low heat to minimize oxidation.
- Oven roasting – Toss chopped veggies with oil before roasting.
- Stir frying – Quickly stir fry ingredients in a skillet on high heat.
- Pan or grill searing – Brush on vegetables, meat or fish before searing.
Avoid prolonged high heat cooking, deep frying, and reusing oil. Heat, air, and time rapidly degrade olive oil’s quality.
What to Substitute for Rancid Olive Oil
If you discover your olive oil is rancid, swap it out for a fresh bottle or try another healthy oil instead. Options include:
- Avocado oil
- Walnut oil
- Grapeseed oil
- Sunflower oil
- Canola oil
- Coconut oil
- Almond oil
- Peanut oil
For dressings and drizzling, nut oils like walnut and almond oil make good alternatives. Avocado oil has a mild flavor that works for cooking.
Match the substitute oil to how you use olive oil. Lighter oils like canola or grapeseed are better for high heat cooking. Nut oils are best unheated.
Storing Different Oils
Like olive oil, other cooking oils have a limited shelf life once opened. Follow these storage guidelines:
- Coconut oil – 2 years unopened, 6-12 months opened
- Avocado oil – 6 months unopened, 4-6 months opened
- Walnut oil – 9 months unopened, 3 months opened
- Grapeseed oil – 6-12 months opened
- Almond oil – 12 months unopened, 6 months opened
Times can vary based on storage conditions. Buy small bottles, limit light and heat, and refrigerate oils after opening to maximize freshness.
Signs of Rancidity in Other Oils
Like olive oil, other cooking oils exhibit signs when they have gone bad:
- Smell – Rancid, off odors
- Color – Darkening from clear golden to yellow or brown
- Texture – Increased viscosity, thicker and cloudier
- Taste – Bitter, soapy, metallic, or stale flavors
- Smoke point – Smoking earlier at lower temperatures
Discard any oil with these defects, as rancidity is irreversible. Never consume or cook with spoiled oil.
Olive Oil Storage Guide
Follow these tips to store olive oil correctly and prolong its shelf life:
- Choose opaque, dark bottles
- Buy only as much as you’ll use in 3-6 months
- Keep bottles out of light in a cool, dry place
- Limit oxygen exposure – keep bottles full
- Use up opened oil within 1-2 months
- Refrigerate oil if not using soon
- Freeze extra virgin olive oil for long term storage
- Check for signs of rancidity before use
- Discard spoiled, oxidized olive oil
Proper storage helps olive oil retain its flavor, aroma, nutrients and health benefits. Follow these guidelines to avoid rancidity.
Frequently Asked Questions
Does olive oil need to be refrigerated?
Olive oil does not need to be refrigerated if you will use it within 2-3 months. For longer storage, refrigeration is recommended. The cold helps slow down oxidation.
Can you get sick from rancid olive oil?
No, rancid olive oil does not make you sick. It has an unpleasant taste and lacks nutrients, but it does not contain harmful bacteria that can cause illness or infection.
How do restaurants keep olive oil fresh?
Restaurants prevent rancidity and maximize freshness by storing olive oil properly, buying small quantities often, and avoiding reuse of cooking oils. They follow ideal storage conditions.
What makes olive oil turn bad?
Olive oil turns bad through oxidation. Exposure to air, light, and heat degrades the oil over time. Its beneficial plant compounds deplete, leading to rancid smells, tastes, and textures.
Can you restore spoiled olive oil?
Unfortunately no, once olive oil has gone rancid and been oxidized, it cannot be restored to its original fresh quality. The only option is to throw away spoiled olive oil.
Olive oil exposed to air ultimately goes rancid due to oxidation. Luckily, proper storage helps maximize shelf life. Buy small bottles, limit light and oxygen exposure, keep olive oil cool and tightly sealed, and use within 3-6 months of opening. Refrigeration and freezing can prolong freshness. Check for signs of rancidity before consuming olive oil. Discard any oil that smells, tastes, or looks defective, as rancidity in olive oil and other cooking oils cannot be reversed.