Demystifying fats and oils, part two

Demystifying fats and oils, part two

Demystifying fats and oils, part two

Why can only certain fats be used in cooking, meaning heated to high temperatures?

Why should others only be used unheated?

Our main concern when it comes to consuming fats and oils is rancidity. Some oils are more prone to rancidity than others. The deciding factor is the chemical makeup of a particular oil or fat.

The building blocks of fats are called fatty acids. They come in three forms: saturated, monounsaturated, and polyunsaturated.

The saturated fatty acids are straight chains of carbon atoms with two hydrogen atoms attached to each. Because of their straight shape, the chains pack together well and form a semisolid consistency at room temperature. Butter, ghee (pure milk fat, also called clarified butter), lard (from pork), tallow (from beef), coconut oil and palm oil consist predominantly of saturated fatty acids. These are very stable and do not become rancid easily. They can be heated to high temperatures without a compromise in quality. They can be used for cooking, baking, sautéing, and with the exception of butter, frying. Butter, because it is not pure fat, is not well suited for frying—its lactose and protein particles tend to burn and turn black rapidly. Ghee, on the other hand, because it is pure milk fat, does work well for frying. For the same reason, ghee is suitable for those with lactose intolerance. But regular butter is fine when heated in gentler ways. It is an especially good compliment with steamed vegetables—add some at the end of the cooking process to ensure absorption of fat-soluble vitamins and enhance taste. 

The monounsaturated fatty acids have one double bond between two carbon atoms, leaving the two double-bonded atoms with only one hydrogen atom each and causing a bend in the chain. Because of this bend, monounsaturated fatty acids do not pack together as well as the saturated ones. They become liquid at room temperature and remain solid only when refrigerated. Olive oil is the most commonly used oil that consists of mainly monounsaturated fatty acids, but almond, avocado, cashew, macadamia, peanut and canola (or rapeseed) oils are monounsaturated as well. These fatty acids are fairly stable and are therefore suited for cooking, baking and sautéing.

The polyunsaturated fatty acids have two or more double bonds—two or more bends—which means their molecular structure resembles that of a semicircle. They do not pack well together at all and are therefore liquid even when refrigerated. Common oils with high polyunsaturated fatty acid content are made from corn, flaxseeds, grape seeds, pumpkin seeds, safflower seeds, soybeans, sunflower seeds, walnuts, wheat germ and sesame seeds.

Rancidity is the main problem with all polyunsaturated fatty acids. Light, air, and heat affect their freshness and quality. Therefore, oils containing predominantly polyunsaturated fatty acids should never be heated or used in cooking. They can be used in cold dressings or sprinkled over cooked food when served. They should always be kept in the refrigerator.

Polyunsaturated fatty acids fall into two main groups: omega 3 and omega 6. These names reflect the location of the first double-bond at either the third or sixth position in the chain. Omega 3 is very reactive and goes rancid particularly easily.

Omega 3 and 6 are called essential fatty acids because our bodies cannot manufacture them and we need to get them from food. Most of the polyunsaturated oils have larger amounts of omega 6 than omega 3. Flaxseed is the exception, with a higher proportion of omega 3. When it comes to the balance between omega 3 and omega 6, the best ratio for human consumption is 1:2. Too much omega 6 can lead to inflammation and blood clotting. Omega 3, on the other hand, is anti-inflammatory and blood-thinning. Because of the recent overemphasis on polyunsaturated oils, many people are consuming too much omega 6 and are in need of omega 3 to return to a place of balance—hence the popularity of flaxseed oil and omega 3 fish oil.

Now that you have an understanding as to which oils are predominantly saturated, monounsaturated and polyunsaturated—and you can always check the proportion of each by reading the package label—you know which oils are suitable for cooking and which are to be used only cold: use saturated oils and fats, such as ghee, lard, coconut oil and palm kernel oil for cooking at high temperatures, use monounsaturated oils, such as olive oil, almond oil and peanut oil for light cooking like sautéing and baking and use polyunsaturated oils, such as pumpkin seed oil, sunflower seed oil and walnut oil cold in dressings or sprinkled over your cooked food as you serve it.

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