Healthy cooking with oil

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Wednesday, 17 March 2010 14:38

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Healthy tips for cooking food in oil

Keri Strachan

If you must cook with oil, proper cooking with the right oil can make all the difference to your health. You’ll remember that (generally speaking) plant fats or oils are the ‘healthy’ fats while animal fats are ‘unhealthy’ fats. The latter can cause high cholesterol levels which may lead to heart disease. A few exceptions to the ‘plant fats are healthy’ rule are palm kernel oil and coconut oil, which contain mostly saturated fats and are likely to raise blood cholesterol levels.

Also, plant products that have been hydrogenated (a process that makes liquid vegetable fats solid at room temperature) will contain levels of trans fats, which have a negative health impact (eg. baked products like biscuits, rusks, crisps, fried foods and fast foods). Another issue of concern is that inherently healthy plant oils, when heated beyond their smoking point, can change structure and become unhealthy fats.

Cooking with oils

The smoking point of an oil is the temperature at which the fat begins to smoke and smell. It depends on the percentage of free glycerol in the fat or the degree to which the molecules are hydrolyzed to free glycerol. When fat is overheated, it emits smoke containing acrolein as a result of the dehydration of glycerol. This production of free fatty acids during deep-fat frying contributes to the lowering of the smoke point. Every time the oil is used again, the smoke point will be lower because the hydrolysis of fat molecules has already taken place. When this happens, toxic products may be produced which could be harmful to your health.

The higher the smoking point of an oil, the better it is for cooking. It is important to remember that the smoking point of oil can be reduced by processing, repeated use, age and improper storage (eg. olive oil in a clear glass rather than a darkened green or brown bottle). Fortunately, most of the cooking we do at home will not lead to such a change in structure of the oil, unless the oil is re-used. This sort of damage to cooking oils is more likely in commercial food retailers, where oils are heated for long periods, and used repeatedly.