Olive oil is a staple in many kitchens and is commonly used for cooking, dressings, marinades, and more. With its high smoke point, olive oil is generally considered a good option for high heat cooking like sautéing, stir-frying, and pan frying. However, there are some conflicting ideas about whether olive oil can go rancid when exposed to high temperatures.
What causes olive oil to go rancid?
Olive oil is made up of mainly monounsaturated fats, which are relatively stable. However, olive oil also contains polyunsaturated fats which are more vulnerable to oxidation. Oxidation is the main cause of rancidity in oils and fats. When the double bonds in polyunsaturated fat molecules are exposed to oxygen, light, and heat, they can form free radicals and break down, causing the oil to go rancid. The free radicals lead to unpleasant flavors and odors.
The level of polyunsaturated fats varies among different types of olive oil. Regular olive oil tends to have a higher percentage of polyunsaturated fats at around 8-15%, while extra virgin olive oil has a lower amount at under 5%. The higher the polyunsaturated fat content, the more susceptible the oil is to rancidity.
Does heating olive oil cause it to go rancid?
Heating olive oil does not necessarily make it go rancid immediately. Olive oil is relatively stable with its high monounsaturated fat content and antioxidant compounds like polyphenols. However, heating olive oil, especially for prolonged periods at very high temperatures, can accelerate the oxidation process and breakdown of the oil over time.
One study examined the effects of deep frying on olive oil. The researchers deep fried potatoes in extra virgin olive oil for over 24 hours across 4 consecutive days, at temperatures between 180-190°C (356-374°F). They found that the olive oil showed signs of thermal oxidation after the first day, but did not show substantial increases in rancidity indicators until the 3rd and 4th day of prolonged, intense frying.[1]
Another study heated olive oil at 190°C (374°F) continuously for 36 hours. They found an exponential increase in oxidation compounds starting after 10 hours, indicating the oil was going rancid with this extreme heating.[2]
So while brief exposure to high heat such as light sautéing or stir-frying is unlikely to make olive oil go rancid immediately, prolonged and repeated heating at very high temperatures can accelerate its oxidation and rancidity over time.
Signs that olive oil has gone rancid from heat
Here are some signs that olive oil has gone rancid from excessive heating:
- Change in color – Oil may turn darker and change from green to gold/orange hues
- Unpleasant smell – Rancid oil gives off a stale, unpleasant odor
- Bad taste – Oil develops a bitter, unpleasant taste
- Smoking – Oil may start smoking at a lower temperature than when fresh
- Foaming – Oil foams up quickly when heated
- Thickened texture – Oil becomes thicker and stickier
Factors that affect olive oil stability at high heat
There are a few key factors that can impact how quickly olive oil will oxidize and go rancid under high heat cooking conditions:
Olive oil type
Extra virgin olive oil has higher amounts of antioxidants and monounsaturated fats that make it more stable than regular olive oil. However, it still contains some polyunsaturated fats that can oxidize. EVOO is best for lower temperature cooking.
Regular olive oil and light olive oil have higher polyunsaturated fat content so will break down faster under high heat. Use refined varieties for higher temperature cooking instead.
Pomace olive oil made from the dregs of the oil making process is highly refined but has very little antioxidants. It is more prone to going rancid from heating.
Smoke point
Oils with lower smoke points like extra virgin olive oil (325-375°F or 165-190°C) are more likely to degrade and go rancid with prolonged heating near their smoke points compared to oils like avocado oil over 400°F (200°C).
Cooking time and temperature
The longer olive oil is heated and the higher the temperature, the more rapidly it will oxidize. High heat methods like deep frying and double frying can accelerate rancidity over time.
Foods cooked
Frying battered and breaded foods can speed up oil breakdown since the bits left behind in the oil cause more oxidation. Moist ingredients like meat also accelerate oxidation more than dry foods.
Presence of antioxidants
Adding spices and herbs high in antioxidants like rosemary, oregano, thyme, garlic, and onions can help protect olive oil from oxidation at high heats. They neutralize free radicals.
Age and storage
Fresher olive oil will be more resistant to rancidity. Properly storing olive oil in cool, dark places in containers that limit light exposure will help prolong its life.
Tips for heating olive oil safely
Here are some tips to minimize olive oil going rancid when cooking at high temperatures:
- Choose light, refined, or pure olive oil for high heat cooking instead of extra virgin.
- Avoid prolonged heating above the smoke point – use oils with higher smoke points here.
- Don’t reuse olive oil after deep frying – dispose of it properly instead.
- Add spices and herbs like rosemary, thyme, and oregano to help protect the oil.
- Store olive oil properly in cool, dark places to prolong its life.
- Use olive oil in shorter duration techniques like sautéing, stir frying, and pan frying.
- Switch out olive oil frequently when cooking in batches to prevent overheating the same oil.
- Look for signs of olive oil degradation like smoking, foaming, and color changes.
Cooking methods best suited for olive oil
Because of its moderate smoke point and susceptibility to oxidation at very high temperatures, olive oil is not necessarily the best choice for all high heat cooking applications. Here are some of the best uses for olive oil:
Pan frying and sautéing
Olive oil works well for quick pan frying or sautéing at moderately high temperatures around 365°F (185°C) for a short time. Use it to pan fry meats, eggs, vegetables, fish and more.
Stir frying
The constant motion of stir frying prevents olive oil from overheating too much. Use it for stir fries at around 375°F (190°C).
Light baking
Olive oil can be used for baking items at moderately high oven temperatures up to around 400°F (200°C). It works well in muffins, quick breads, cookies, and cakes.
Dressings and marinades
Olive oil is excellent for making salad dressings, herb infused dipping oils, pestos, and marinades that don’t require any cooking.
Lower temperature cooking
Extra virgin olive oil is great for more gentle cooking methods like poaching, making omelets, roasting vegetables, or making aioli spread.
High heat cooking oils better than olive oil
For very high heat cooking methods like deep frying, double frying, or wok cooking, olive oil is not the best choice. Here are better high heat cooking oil options:
Avocado oil
Avocado oil has a very high smoke point of 520°F (271°C) and is more stable than olive oil when heated. Use for deep frying, searing, and high heat stir frying.
Refined coconut oil
Refined coconut oil can withstand heat up to 450°F (232°C) and has little risk of going rancid. Use it for deep frying donuts, fritters, and breaded foods.
Peanut oil
With a smoke point of 450°F (232°C), peanut oil makes a good option for deep frying, stir frying, and pan frying at very high heats.
Grapeseed oil
A light, neutral flavored oil like grapeseed oil has a smoke point around 420°F (216°C) making it suitable for deep frying and oven cooking.
Should you avoid heating olive oil altogether?
No, you don’t necessarily need to avoid using olive oil for all high heat cooking. Olive oil is a versatile, healthy cooking oil. Just keep a few things in mind:
- Use olive oil for quick cooking over moderately high heat like sautéing or stir frying.
- Avoid prolonged heating over its smoke point which can make it degrade.
- Don’t reuse olive oil after deep frying – discard it instead.
- Opt for a more heat stable oil for very high temperature cooking like deep frying.
- Store olive oil properly and use it within a couple months to maximize freshness.
Being aware of its smoke point and using olive oil properly will allow you to take advantage of its delicious flavor in high heat cooking safely.
The bottom line
Olive oil can go rancid and degrade when exposed to excessive heat over time. However, brief exposure to moderately high heat such as quick sautéing won’t immediately make olive oil go bad. Just avoid prolonged heating over its smoke point which accelerates oxidation. Additionally, choose a highly refined or light olive oil over extra virgin for cooking at very high temperatures. With the proper care and usage, olive oil can be deliciously incorporated into high heat cooking.
