Because stir-frying involves cooking food at high heats, its important to choose oil that has a high smoke point. The smoke point is the temperature at which an oil (or other type of fat) begins to break down. Oil that is heated to its smoke point or higher will begin smoking and start to impart a bitter taste to the food. Furthermore, because the oil is breaking down at the molecular level, it can produce carcinogens.
Choosing a Stir-fry Oil
Chinese cooks normally use peanut oil, which has a high smoke point and a pleasant nutty flavor, for stir-frying (and deep-frying). Canola oil, which has a high smoke point and a neutral flavor, is also a good choice. So is pure olive oil (also simply called olive oil) but not the extra-virgin varieties. Other possibilities include corn, soybean, and coconut oil.
What About Grapeseed Oil?
Another oil that is becoming more popular for stir-frying is grapeseed oil. Made from the seeds of grapes after the wine is pressed, grapeseed oil has a clean flavor and a high smoke point (420 degrees Fahrenheit). What makes grapeseed oil so attractive is that it has similar health benefits to olive oil, but with a more neutral flavor. (Although I don't have this problem very often, it is true that the flavor of the olive oil can sometimes conflict with other flavors in a stir-fry dish).
Which Stir-fry Oils are Healthiest?
Both Canola oil and olive oil are low in unhealthy saturated fat, and high in healthy monounsaturated fat. Scientists believe monounsaturated fats help lower the bad cholesterol (LDL ) that can clog arteries, leading to heart disease or stroke, while increasing the level of good cholesterol (HDL) that removes cholesterol buildup from the arteries.
Grapeseed oil is low in saturated fat and high in polyunsaturated fat, which scientists believe can also help raise HDL levels. Grapeseed oil is also a good source of linoleic acid a type of essential fatty acid which, like the Omega-3 fatty acids found in salmon, cant be manufactured by our bodies and must be obtained from food.
Asian Sesame Oil - Use for Seasoning, Not Stir-frying
Its strong flavor and unstableness when heated makes Asian sesame oil unsuitable as a stir-fry oil. It is used primarily as a seasoning, added to the stir-fry at the end of cooking.