While it is definitely true that fats and oils carry flavor molecules and conduct heat for cooking, they start breaking down at smoke point. The smoke point of an oil or fat is the stage when it stops shimmering (sign of oil readiness), and starts producing smoke during cooking. At this point, the oil is starting to break down due to overheating. What exactly occurs here is that the fatty acids are released from the glycerol forming into longer polymers that create the unpleasant, bitter or burnt taste. Furthermore, the glycerol reacts with oxygen with a high temperature, forming water and acrolein. Acrolein is an unsaturated aldehyde. It can irritate soft tissues and may cause dizziness, nausea, and headache.

Knowing the smoke point of oils is essential— it saves you from cooking food that is not supposed to taste burnt or bitter. Plus, it minimizes the production of free radicals (reactive chemicals that damage cells) as a result of overheating. Below are the smoke point of some of the common cooking oils for your reference.

Smoke point of common cooking oils

What affects the smoke point of fats and oils?

As you may have already noticed, fats and oils smoke or burn at different temperature. And it depends on several factors, including the fat or oil’s composition, the refinement level of the oil, and the condition of the cooking set up (volume or amount of oil, container size, etc..).

There are 3 main types of fatty acids: saturated, monounsaturated and polyunsaturated. Among these three, more saturated fats tend to decompose faster. This is why butter, which is naturally rich in saturated fats (50%-63%) smokes (at 302 °F) quicker than most types of fats. For a better picture, a refined corn oil, which is only 13% saturated fats can have a smoke point of around 446 °F (230 °C). Safflower oil, which contains around 75% polyunsaturated fats and 12% monounsaturated fat, has one of the highest smoke points.

Another thing that makes butter not ideal for certain cooking method, particularly for sautéing, is its lactose content. Although it only contains trace amount of lactose, it readily burns when heated. When sautéing, what chefs do is remove the protein (milk solids) and water, leaving only fat—or clarified butter. Clarified butter has a smoke point of 482 °F (250 °C).

You might also like: The Science Behind Why Food Sticks to Cast Iron (And How to Prevent It)

Basically, less refined oils have lower smoke points. These oils contain more impurities such as minerals, enzymes, free fatty acids, and other impurities that have a tendency to burn faster. For this reason, unrefined oils are better used in low heat applications. Moreover, unrefined oils turn rancid more quickly, and are less shelf life stable than their refined counterparts. If stored properly, most unrefined oils last for 3 to 6 months.

Which oil to go for?

When choosing oil or fat, smoke point is just one of the few factors to consider.

Generally, you would want to go for fat or oil that has a high smoke point, especially for cooking food that require high heat. Frying require a cooking temperature between 350 °F (177 °C) and 375 °F (191 °C). Peanut oil, almond oil, and safflower oil have high smoke points. Oils with a high smoke point are ideal for stir-frying and deep drying. The higher the smoke point, the better.

What is the flavor requirement of the food? If you want the oil to impart a mild flavor to fried food, you can not go wrong with olive oil. Olive oil is typically a mix of refined and unrefined oil. Extra virgin olive has a lower smoke point than the regular olive oil. With a smoke point of 320 °F (160 °C), it is not suitable for frying, but is used best for drizzling over vegetables or as a base for salad dressing. While oils like peanut oil may have a high smoke point, its mild and nutty flavor usually is retained even after cooking.

If you want an oil that are healthier, opt for an unrefined one. Unrefined oils not only retain the natural flavors, but the enzymes, nutrients and mineral as well. However, again, they have low smoke points, so they are better used for minimal heat cooking or food that do not require cooking like salads or vegetables. To make sure the oil is unrefined, read the label and look for words such as “unrefined”, “virgin”, or “cold-pressed”.

Also go for an oil that contain more unsaturated fats. They are called “good fats” for a good reason— beneficial for the heart and overall health. Extra virgin olive oil contains the highest amount of monounsaturated fats. Aside from having a high smoke point, peanut oil, avocado oil and safflower oil are rich in oleic acid, an unsaturated fat.

Reusing of oil and free fatty acid level

It is totally fine to reuse cooking oil for a few times. However, it is a good idea to know when to discard used oil. Set a limit when using used oil. Cooks Illustrated recommends to use oil only 3 to 4 times for breaded and battered foods, while use oil for up to 8 times at least, if used for cleaner foods like potato chips.

Repeated cooking will accumulate the free fatty acids in the oil. Free fatty acids (FFA) are the products of hydrolysis of oils and fats during cooking. The more the oil is reused, the higher the FFA levels, and the lower the smoke point. Specially refrain from using used oil for cooking food that requires high cooking temperatures. Oils and fats impart that unpleasant bitter taste in food as soon as they hit their smoke point.

The post Fats & Oils: What Exactly Happens At Smoke Point? appeared first on The Food Untold.