Frying is definitely a common practice, and to be honest there’s an amazing taste that fried food has crunchiness. But what if I told you that frying or burning oil changes its molecular structure making it poisonous, would you still enjoy that crunchy chicken or deep-fried potato wedges?  

I had a unique opportunity to sit down with Udo Erasmus, an oil researcher and nutritionist, author of Fats that Heal and Fats that Kill, on YellowTape Installment 23 to unpack the risk associated with cooking with oil.

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Until the 1920s oil wasn’t widely used for cooking. According to Udo, oil producers identified this as a great source of income and started running campaigns that included changing it from frying oil to cooking oil. This led to the mindset shift that influenced the widely accepted practice of cooking with oil. Egyptians can be traced historically as one of the first people to use oil in their food, and initially, the oil was used to provide a taste to the food and not cook with oil. Cooking was done by water. 

When cooking oils are subjected to heat in the presence of air and water (from food), such as in deep-fat frying and sautéing (pan-frying), they can undergo at least three chemical changes: 1) oxidation of the fatty acids, 2) polymerization of the fatty acids, and 3) breaking apart of the triglyceride molecules into free fatty acids and glycerol by hydrolysis (reaction with water from the food being cooked) (Choe and Min 2007). 

All three chemical changes increase with cooking time and temperature and are accelerated by the presence of food. When it comes to the health aspects of cooking with vegetable oils, oxidation of the fatty acids is very important. During cooking, oxidation of fatty acids, both free and in triglycerides, produces very small amounts of dozens of new compounds called aldehydes, ketones, and alcohols. These compounds produce the wonderful flavours of fried foods. But in sufficient quantities, some of these compounds can be toxic. (IFT).

A bit of explanation, oxidation is the process of gaining oxygen. A volatile aldehyde is produced in vegetable oils by the oxidation of linoleic acid which is responsible for much of the enticing aroma of fried food.

Of the vegetable oils that have been tested for heating-induced aldehyde content, olive oil actually performs reasonably well. Researchers from the University of the Basque Country analyzed olive, sunflower and flaxseed oils for their aldehyde content after the oils had been heated to 190℃. They found that heating the polyunsaturated sunflower and flaxseed oils produced greater quantities of aldehydes more quickly, whereas heating monounsaturated olive oil created fewer aldehydes and much later in the heating process.

In discussion, Udo highlights more details covering the effects of the various oils. Udo also understands how important fats are to the human body and he shares alternatives of getting the oils from natural sources. Udo goes on to explain how to store oil and eat healthily.

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