We discussed in my latest blog post, Health Effects of Rancid Fat in your Diet, how oxidation can negatively effect your health. Fats and oils can go rancid when they are exposed to light, air, or heat over a period of time. Another important aspect is the smoke point. Let's discuss what to consider to allow you to choose the best cooking oil.
Heating oils to higher temperatures than they are able to withstand should be avoided. All oils have a natural smoke point (AKA burning point). This is the temperature at which an oil or fat begins to produce a continuous bluish smoke. Chemicals are released that give food an unpleasant burnt or bitter flavor. This also results in oxidation of the fatty acids (produces free radicals) and can have negative health effects over time.
Each type of oil has it's own unique chemical composition. Some are better suited for salad dressings while others can stand to be heated to high temperatures when roasting or frying. Always consider the temperature you'll be cooking at before you choose what type of oil to use.
Oils labeled as Unrefined, Cold Pressed, or Expeller Pressed should not be heated. They are processed by using sheer force to extract the oil vs. any chemical means. They are unstable when heated. These oils are most often seen as nut or seed oils like Walnut, Pumpkin Seed, Hemp Seed, Sesame, Extra Virgin Olive, or Raw Coconut. They are usually darker in color than their refined versions and also more flavorful.
Nutrition Dynamix'es Guide for Choosing the Best Cooking Oil:
As discussed in my latest blog, Health Effects of Rancid Fats in your Diet, where you buy your oil and how you store it can effect it's healthfulness. Learn more about everything you should consider when buying, storing, and using fats and oils in 6 Tips for Avoiding Rancidity.