Cooking with Oil

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What happens to oil in the pan

EVIDENCEREVIEW 1

READ THE ORIGINAL

Oil in a hot pan is not just getting hot. Three things happen at once: water hydrolyzes it into free fatty acids, oxygen oxidizes it, and the oxidation products link up and polymerize, so the oil thickens and darkens.

How fast it degrades depends mainly on four things: how hot it gets, how many times the oil has been used, how much unsaturated fat it holds, and whether metals such as iron or copper have gotten in. During frying, the vitamin E (tocopherols) in the food is broken down too.

So a smoke point answers one question: at what temperature the oil starts to smoke visibly. It cannot tell you how oxidized the oil is — smoke point is not one of the four things that set how fast oxidation goes. Why more double bonds mean more oxidation is explained at the molecular level in Olive Oil.

A CLOSER LOOK

Smoke point does not measure oxidation

This shows oxidation followed by polymerization. Hydrolysis in contact with water is a separate concurrent pathway. Arrows show relationships, not speed or risk size.

Heating conditions: Temperature, reuse, unsaturation and metals affect the rate. Smoke point alone cannot answer this question.
Products link up: Oxidation products can polymerize, thickening and darkening the oil. Color cannot be translated into a numerical risk.

Illustration for understanding; not to scale. Saved figures include explanations and sources.

Educational content, not medical advice — consult a clinician.

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