Cooking oils are ingredients most of us likely use every day. We use them to cook veggies, dress up a salad, bake, to marinate meats and more. These fats provide nutrition we need and flavor we love. They also assist in absorption of fat-soluble nutrients (such as vitamins A, D, E, and K) and they help us during the cooking process (such as coating veggies so they don't stick to our pans). One term that often gets thrown about when it comes to oils is "smoke point". This is the temperature at which oil starts to smoke continuously. It doesn't refer to the point where you see a tiny bit of smoke but rather a continuous production of it.
If your oil has reached this point during cooking, it has reached a point where nutrients in the oil are breaking down and oxidizing. Not only are the nutrients getting damaged but harmful ones are being produced. This oxidation can create potentially harmful free radicals. The smoke will eventually produce acrolein, an irritating chemical that also imparts a bitter flavor and aroma.
Cooking OIls 101
When oils are extracted, they are either left in their natural state or they are processed. Oils left in their natural state are "unrefined", "cold-pressed", "raw", or "virgin". They'll have all the nutrition and flavor you'd expect from the extracted oil. These tend to have lower smoke points, however. They are best used for low-heat cooking or raw recipes (salad dressing, baking, a quick saute, a dip).
Oils are refined or processed in order to raise their smoke points. Typically, they are heated or a chemical is added to them that helps remove any compound in the oil that may oxidize and break down. The downside is they tend to lose some flavor and nutrition in the process.
Know your Cooking OIl Smoke Signals
The main takeaway message is to use oils with higher smoke points for higher heat cooking (such as frying, searing, and stir-frying). High smoke points are any smoke point at or above 400°F. There is a middle ground here, too. Since sauteing does not require extremely hot oil, an oil with a medium or medium-high smoke point, like virgin olive oil or coconut oil, is safe.
Use unrefined, more nutrient dense oils for lower-heat cooking. You'll find these oils have a more robust flavor making them perfect as finishing oils, in vinaigrettes, or dipping sauces.
High smoke point oils (best for browning, deep-frying, searing): Almond, Avocado, Refined Coconut, Cottonseed, Ghee (clarified butter), Hazelnut, Refined Olive, Palm/red palm, Palm kernel, Safflower, Sunflower, Tea seed
Medium-high smoke point oils (best for baking, stir-fries, roasting): Canola (rapeseed), Grapeseed, Macadamia Nut, Extra Virgin Olive, Peanut
Medium/Low smoke point oils (best for sauces, low heat baking, a quick light saute): Coconut, Corn, Hemp, Pumpkin, Sesame, Soybean, Walnut
No heat oils (best for salad dressings, marinades, or dips): Chia seed, Flaxseed, Wheat germ
As its name implies, extra virgin olive oil is unrefined and cold-pressed so it has a low smoke point (325-375°F). This is definitely an oil better used for salad dressings, dips, and low-temperature cooking.
What about olive oil that isn't "extra virgin"? These oils are typically marketed as "light" or "pure". These are refined, processed olive oils so they have a higher smoke point, around 465°F. This makes it a better high temperature cooking oil but it also has less vitamins and antioxidants.
Are you using your cooking oils properly? It might be necessary to store several different oils in your pantry so you have just the right oil for your different cooking needs. This will make it easier to stay below the smoke points of the oils you use!