The Smoke Point of a Cooking Oil: Is it Important?

Cooking Oils

The smoke point of cooking oils refers to the temperature when an oil starts to smoke—which it will reach before its boiling point. Heating oils past their smoking point has been linked to the formation of carcinogens and can also create an off, burnt flavor.

Knowing the difference between oils and their smoke points is an essential part of healthy cooking. Each oil has a different smoke point and will vary depending on whether the oil is refined or not and what the percentage is of polyunsaturated vs monounsaturated vs saturated fats.

Is Consuming Oils Past Their Smoke Point Harmful?

The smoke that is created once an oil reaches its smoke point is an indication of the fat's breakdown. Generally, as a rule of thumb, the smoke point tends to increase the more refined an oil is and as the free fatty acid content goes down. As oil is heated, more free fatty acids are produced which lowers the smoke point.

It is generally recommended to not reuse frying oil more than twice. This is primarily because of this increase in free fatty acid formation and harmful free radicals each time oil is heated through a process called oxidation—a series of chemical reactions involving oxygen that degrade the quality of the oil and lead to rancidity.

In fact, there is a way to measure how much an oil has degraded by measuring the concentration of these by-products called "polar compounds". Polar compounds are also impacted by the moisture content of the food that interacts with the frying oil, its surface area, and how many residual particles are left in the frying oil, among other factors.

However studies indicate that there is a correlation between oils highest in polyunsaturated fats (PUFAs) and production of high amounts of polar compounds when heated. This is one reason why eating deep fried foods is not just unhealthy in terms of its caloric content; these foods can actually contain toxic carcinogenic compounds if cooked in oil that is reheated over and over again and especially in oil that is high in PUFAs. Reheating oil also breaks down the beneficial polyphenol antioxidants, one of the major health benefits of plant-based oils.

Repeatedly heating fats, especially polyunsaturated fats, at high temperatures beyond their smoke point can cause the formation of carcinogenic compounds.

Which Fats/Oils are Best for Cooking?

There are several things to consider when determining the right cooking fat: nutritional value, flavor and cooking technique. Knowing an oil's smoke point provides another piece of information to help guide you when determining what kind of oils are best for particularly cooking methods.

The most important thing to remember, however is to not heat and reheat the polyunsaturated oils beyond their smoke point since these are the oils that are most prone to oxidation and the ones that produce the most harmful compounds when they oxidize.

Nutritional Value

For overall health, the best oils are those high in monounsaturated and polyunsaturated fats. These fats are known to be heart-protective and reduce systemic inflammation in the body. Monounsaturated oils include canola oil, peanut oil, almond oil, olive oil, avocado oil, and high oleic sunflower and safflower oil. Polyunsaturated oils include wheat germ oil, soybean oil, sunflower oil, safflower oil, grapeseed oil, walnut oil, flaxseed oil, and corn oil. Sesame oil has almost equal proportions of monounsaturated and polyunsaturated fats (around 40% each).

After oils are extracted or pressed, they can either be bottled immediately or refined and processed. Oils left in their natural state are labeled as unrefined, cold-pressed, raw, or virgin and are processed without any chemical solvents. These oils tend to have better nutrient retention and higher polyphenol contents. These unrefined oils also tend to have lower smoke points and can turn rancid more quickly, so understanding their smoke points and storing them properly is imperative.

Olive oil, in particular, is known for its high polyphenol levels; these are highest in extra virgin olive oil, which is one of the reasons it is touted for being so healthy. In fact, in order for an oil to be called "extra virgin", it must meet specific minimum polyphenol concentrations.

Yet even among extra virgin olive oils, polyphenol content can significantly vary based on climate conditions in the olive groves, when olives are harvested and how ripe they are when they are picked as well as how the oil is produced and stored. Certain brands of oils will actually test their oil and share information on the polyphenol content (look for content greater than 250mg/kg for an extra strong concentration of polyphenols).

Flavor

The flavor of oils varies considerably. Most unrefined expeller-pressed and cold-pressed plant based oils will have their own unique flavors however some are stronger than others. For example, nut and seed oils such as walnut, almond, pecan, pumpkin seed and sesame oil, particularly the "toasted" varieties, will have strong flavors that resemble the nut they are derived from and are best used as a key ingredient in a dish utilized specifically for their flavor.

Another category of oils, which chefs frequently call "neutral" oils, do not impart a strong flavor and are used primarily for their function as a fat in the cooking process, such as to saute, impart browning or caramelization or to use in frying. Some neutral oils are also commonly used in vinaigrettes if the recipe includes other strong flavors and is primarily using the oil for emulsification, such as in a mayonnaise based dressing. Neutral oils include canola oil, grapeseed oil, corn oil, and avocado oil.

High quality extra olive oil should have a fruity, bitter, and even pungent peppery taste depending on the type of olive used and its origin and processing. Regular virgin and light olive oils, are either a blend of cold-pressed and refined oils or fully refined with a processing method that uses heat and will have a more neutral taste and slightly higher smoke points.

Cooking Technique

After oils are extracted or pressed, they can either be bottled immediately or refined and processed. Oils left in their natural state are labeled as unrefined, cold-pressed, raw, virgin, or unrefined. These oils tend to retain flavors and all of their inherent nutrients.

However, in terms of cooking, the unrefined oils tend to have lower smoke points, will oxidize more easily when heated, and are more likely to turn rancid if not properly stored; these oils are best used for very low heat cooking such as baking or light sautéing, or raw applications like salad dressings or finishing drizzles.

The big exceptions to this are extra virgin olive oil and unrefined avocado oil, which naturally have higher smoke points and because of their high monounsaturated fat content, are more stable when heated. They do not produce the same volatile carcinogenic compounds when they break down like oils high in polyunsaturated fats.

If oils are refined or processed, they will usually be extracted using chemical solvents and also heated to remove the volatile compounds that break down and lead to the quick oxidation of virgin unrefined oils. As a result, these refined oils are less flavorful, have a longer shelf life, and higher smoke points.

As a general rule of thumb, it is usually recommended when frying or cooking at very high temperatures, to use oils that high smoke points (greater than 400F). These oils include refined oils (refined canola oil, coconut oil, peanut oil, avocado oil, corn oil, etc as well as light olive oil, and some solid fats like ghee (clarified butter) and lard.

These fats are also ideal for roasting, since roasting is done at temperatures between 375F-450F. However if sautéing, roasting just at 375F, or pan-frying at temperatures below 400F, using olive oil or extra virgin olive oil for its myriad health benefits and flavor, is perfectly fine! Avocado oil, another oil high in monounsaturated fats, is also a great choice if you are looking for a neutral flavored oil that also has excellent health benefits.

Smoke Points of Different Oils
Oil Smoke Point 
Refined Avocado Oil 520F
Refined or Light Olive Oil 465F
Refined Peanut Oil 450F
Ghee or Clarified Butter 450F
Corn Oil, Sunflower Oil, Safflower Oil 450F
Refined Coconut Oil 450F
Refined Sesame Oil 410F
Canola Oil 400F
Grapeseed Oil 400F
Extra Virgin Olive Oil 375-400F
Duck Fat, Chicken Fat, Lard 375F
Unrefined Virgin Avocado Oil 375F
Unrefined Virgin Coconut Oil, Unrefined Sesame Oil 350F
Unrefined Walnut Oil, Unrefined Peanut Oil 320F
Butter, Walnut Oil 300-350F

Tips for Choosing a Cooking Oil

  1. Think about whether you want the oil to be neutral or impart a particular flavor
  2. Narrow down which cooking oils have the appropriate smoke points for the specific cooking technique you are using
  3. Determine which oil is the healthiest for your particular health goals

Common Questions

Can I Cook With Extra Virgin Olive Oil?

Yes! Not being able to cook with extra virgin olive oil is a myth. While its smoke point is not high enough for deep frying (and it would be very costly), extra virgin olive oil can easily be used for low to moderate heat cooking methods such as baking, roasting at moderate heat, sautéing and pan-frying. It is primarily made up of monounsaturated fats similar to avocado oil so is not as prone to oxidation as the oils high in polyunsaturated fats. In fact, in the Mediterranean region, extra virgin olive oil is pretty much used for everything!

The polyphenol content will start to decrease with heat so it is still good to use extra virgin olive oil in cold applications to get the maximum nutritional value in terms of antioxidants but there are other health benefits from using extra virgin olive oil when cooking such as the high content of heart healthy monounsaturated fats, not to mention its incredible flavor. If extra virgin gets too costly, the next best option is virgin olive oil which will just be a grade below extra virgin but still highly nutritious.

What Is the Difference Between Cold Pressed and Expeller Pressed?

Neither expeller or cold pressed use high heat or chemicals as a method of extraction. Expeller pressed oil is oil that has been extracted using a “screw press” that presses seeds and nuts through a cavity and uses friction and pressure to extract oil. Although no heat is added, some natural heat is created from the friction (around 210F).

Cold pressed oil is extracted using an oilseed press which crushes the nuts and seeds. This is done at a very low temperature (around 120F) and proponents of cold pressed oils claim this is the ideal method for preserving maximum flavor and nutritional value.

Both processes are also more costly for oil producers because they don't produce high yields of oil—this is why many oils are pressed using other methods with chemical solvents and high heat and also why expeller and cold-pressed oils will be priced higher than other oils on the shelves.

What Is Generic Vegetable Oil?

Oil simply labeled "vegetable oil" is usually a blend of different types of oils neutral in flavor. It can be used in baking or everyday cooking and is less expensive than other oils however it is not always possible to know exactly what is in the oil or how it is processed. It is likely a blend of soybean oil with other neutral plant-based oils such as sunflower, corn, or safflower and will have been processed using a chemical solvent.

Should I Avoid Consuming Oils High in Polyunsaturated Fats?

There is no need to avoid consuming oils high in polyunsaturated fats. After-all, all oils contain a combination of both poly-and monounsaturated fats. Oils high in polyunsaturated fats are also healthier than consuming large quantities of saturated fat. But it may be prudent when cooking at higher temperatures and choosing an oil for use on a regular basis, to opt for oils both higher in monounsaturated fats and with higher smoke points that are less likely to degrade when heated.

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Article Sources
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