I understand that the smoke point is the temperature at which oil starts to produce smoke. But how exactly is that smoke produced? I've read that it is related to hydrolysis and oxidation, but I'd like to know a more precise link.
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1$\begingroup$ How "precise" an answer you want? Most oils are mixtures of many different compounds so discussions tend to be general rather than showing a specific chemical mechanism, or a particular overall chemical reaction. $\endgroup$– MaxWJul 21, 2018 at 19:26
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$\begingroup$ @Max Well, at least some examples of reactions or mentions of a family of compounds. $\endgroup$– jinaweeJul 22, 2018 at 7:38
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2 Answers
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Typically smoke point has to do with the composition and amount of free fatty acids in the fat/oil. Most fats and oils that you see on the market are mostly composed of triacylglycerols, with only small amounts of free fatty acids. The more free fatty acids you have the lower the smoke point. Similarly unrefined oils have a low smoke point. If you have fats/oils that contain high levels of unsaturated fatty acids, then that product will also have a lower smoke point than say a fat that contains significant amounts of saturated fat. In regards to the chemical mechanism, upon heating the triacylglcyerol structure gets broken down into free fatty acids and glycerol via a hydrolysis reaction. The free fatty acids volatilize and cause the visible smoke. Unsaturated fatty acid are more sensitive to heat and will be hydrolyzed quicker than saturated fatty acids. For more info read this article: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4424769/
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The smoke point also known as burning point of an oil or fat is the temperature at which, under specific and defined conditions, it begins to produce a continuous bluish smoke that becomes clearly visible.