Smoke point

The temperature at which a fat begins to produce visible smoke as it thermally decomposes. It varies with the fat’s composition, refinement, age, and heating conditions.

Thermal decomposition: The chemical breakdown of a substance caused by heat. Smoke appears as heat breaks down fat molecules into volatile products.
Deep frying: A cooking method that immerses food in hot oil or fat. Frying oil is heated for extended periods, so excessive smoking signals deterioration.
Triglyceride: A molecule consisting of glycerol esterified with three fatty acids; the main component of most dietary fats. Triglycerides are the principal molecules that break down when fats are overheated.
Oxidative stability: A material’s resistance to chemical reactions with oxygen. A high smoke point does not by itself establish resistance to oxidation during prolonged heating.
Hydrolysis: A chemical reaction that splits a molecule through reaction with water. Water and heat can release free fatty acids that contribute to smoking.
Sautéing: A cooking method that quickly cooks food in a small amount of fat over relatively high heat. Its direct, high heat can bring a low-smoke-point fat to visible smoke.
Fatty acid: A carboxylic acid with a hydrocarbon chain, forming a component of fats and oils. Fatty-acid structure helps determine a fat’s stability under heat.
Thermal stability: A substance’s ability to retain its chemical structure when heated. It describes a broader response to heat than the visible onset captured by smoke point.
Free fatty acids: Fatty acids not bound within larger molecules such as triglycerides. Their presence generally lowers the temperature at which a fat begins to smoke.
Clarified butter: Butterfat separated from most of butter’s water and milk solids. Removing milk solids raises its smoke point compared with ordinary butter.

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