What is oil smoke point?
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/