There are many different issues to consider when it comes to choosing a cooking oil. Taste is just one factor. Fat content is another factor. Obviously, in the context of this column, how the oil may affect your health is a major factor. Last January, the Journal of the American College of Cardiology published a research article that found that people who consumed more than 7 grams (0.25 ounce) of olive oil exhibited a significantly lower risk of death. Olive oil is a major component of the Mediterranean diet, a very healthy and heart-conscious diet.
Saturated fat raises levels of LDL, or “bad” cholesterol. Polyunsaturated fats are better, but the healthiest fats to consume are unsaturated, or monounsaturated fats. Oils that contain high levels of saturated fat include coconut, palm, and palm kernel oil. Incidentally, a number of oils are made from nuts, which concerns those with nut allergies. Be not afraid. Oil is lipid that is extracted from the nut. In most cases, those with nut allergies are reacting to surface proteins found on the nut. Therefore, those with nut allergies can usually safely consume oil made from that nut, although you might want to check with your allergist first.
Heating oil can change its characteristics. Oils that are healthy at room temperature can become unhealthy when heated, especially if reheated multiple times. This is because heating the oil oxidizes the fatty acids that some oils contain, creating chemicals, some of which may be carcinogenic. An oil’s resistance to change when heated is called heat tolerance. Some oils, if used, for example, in a deep fryer (avg. temp. 338 to 374 degrees), may need to be changed a few times a week. It has been recognized since the early 1900s that palm oil can withstand high heating and resist oxidation, making it ideal for use in deep fryers. It is also stable at high temperatures making it good for high-temperature commercial baking. Plus, palm oil is high in antioxidants. The trade-off (isn’t life full of them) is that palm oil is high in saturated fat. That is why deep-fried foods should be consumed in moderation.
Oil also degrades when exposed to heat, light, or oxygen, which is why it comes in tinted bottles or metal containers. Manufacturers often place a layer of an inert gas like nitrogen at the top of the container before sealing it. This is called blanketing and prevents exposure to oxygen. The smoke point is the temperature at which the oil begins to burn. Fatty acids in the oil are responsible for the oil burning. Refining, which removes fatty acids, gives the oil a higher smoke point. Foods cooked in smoking oil will have a burnt flavor. The flash point is where the vapors ignite but do not remain lit. As this is usually above 500 degrees, it will not normally affect household use. Even higher is the fire point where the oil vapors will ignite and burn. Lastly, margarine is made from oils and should never be used for frying because, as an oil, it will undergo chemical changes when heated. It may, however, be used for baking if butter cannot be used.
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