Cooking with oils is pretty common in North American food preparation. While some types of oils are better suited to heating at these high temperatures, what has been firmly established is that when oils are exposed to high temperatures they are subject to a number of chemical reactions. Side effects of these reactions (particularly oxidation reactions) can be volatile, evaporate off, or may be non-volatile in which case they mix into the oil or are added to the food. Reuse of these oils is prevalent in the restaurant industry, particularly for deep frying. Reheating vegetable oils that are normally good for cooking, such as coconut oil, can also produce polycyclic aromatic hydrocarbons (PAH’s) which can be carcinogenic. So basically, avoid deep frying especially in old oil of any kind. But that doesn’t mean that you should avoid consuming oil in general. In fact there are many health benefits to consuming healthy fats as oils. The most notorious benefit of course is the cardiovascular benefits of good oils.
So what makes an oil good?
- Saturation of fatty acids in the oils- saturated vs. unsaturated refers to the number of double bonds of the fatty acid chains. When an oil is composed of unsaturated fatty acids it has multiple double bonds, this causes kinking in the chain meaning that it’s harder for the chains to pack close together. Think of it like oil in your car; you want it to flow even when it’s cold, you don’t want it to pack together, clump up and get stuck. Unsaturated oils are usually liquid at room temperature and can solidify when cooled (how quickly this happens depends on the number of double bonds present). Oils with high unsaturated fatty acid content, such as virgin olive, palm, and safflower oil are great bases for salad dressings. Saturated fats on the other hand can pack together, generally making them more solid at room temperature. Consuming excess saturated fats has been linked to cardiovascular disease because it increases your total cholesterol as well as your LDL (low density lipoproteins) or “bad cholesterol.” These fats are high in butter and margarine. That being said, coconut oil has a high percentage of various short and medium chain saturated fatty acids. This makes it solid at room temperature though less so than butters and a small amount of heat can liquefy it. Coconut oil is the better option for frying or sauteing with since it starts as a solid it takes longer to breakdown and form those oxidative byproducts we talked about earlier, yet is still has less risk than the highly saturated butters.
- Configuration- unsaturated fatty acids can either be oriented in a cis-configuration (meaning they are on the same side) or a trans-configuration(meaning opposite sides). The trans-configuration is usually the result of partial hydrogenation during oil production, meaning it’s not the common natural form as it allows for closer packing of fatty acid chains and has also been well documented as increasing risk for cardiovascular disease. Trans fatty acids are high in palm oil and butter.
- Number of Double Bonds- unsaturated fatty acids may have one double bond (monounsaturated fatty acids, MUFA) or many (polyunsaturated fatty acids, PUFA.) For example, soy oil has about 60% PUFA’s, 24% MUFA and 16% saturated fatty acids. While palm oil is composed of MUFA’s and saturated fatty acids. Both MUFA’s (avocado and olive oil) and PUFA’s (fish oils or omega 3 fatty acids from algae) have shown cardiovascular benefits as increasing HDL or “good” cholesterol, reducing your LDL and total cholesterol, improving brain function and much more. High heat can break apart some of these double bonds so they are best consumed cold.
- Length of fatty acid chains– whether saturated or unsaturated the length of the chain is also associated with different health benefits. Coconut oil has more short and medium chain fatty acids that can tolerate heat longer than olive oil.
- Potential to form harmful oxides- some oils can form harmful, even carcinogenic oxides when heated. For example, sunflower oil produces two times more harmful oxides than olive oil when heated for the same amount of time at the same temperature. Making olive oil a relatively better option for cooking.
- What else is in the oil? coconut oil has molecules called tocotrienols, polyphenols, and tocopherols which give it antioxidant protection, while palm oil is richer in tocotrienols only, and soy oil primarily has tocopherols. Both tocopherols and tocotrienols are the molecules that form the Vitamin E complex– and both groups of molecules have health benefits though they are best when combined. The best oils have a diverse range of beneficial, biologically active, compounds that can mitigate some of the negative by-products formed at high temperatures.
So tell us what are your favourite oils to be cooking with?
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