Influence of Short-Term Heating on Composition of Edible Fats

A number of edible fats were heated at 235 ± 5°C and the extent of hydrolysis determined after 20, 40, 60, 90 and 120 minutes. There was some hydrolysis in all cases, but the extent of hydrolysis of any individual fat does not appear to be correlated with composition, iodine number or initial free fatty acid titer. Starting free fatty acid titers ranged between 0.03% (coconut oil) and 2.13% (cod liver oil) and increased as high as 17.78% (cod liver oil), although in most cases free acid titers after two hours of heating were below 1%. Several specially hydrogenated fats were also tested and on heating, behaved like the commercially available materials. There was very little change in iodine value during the heating experiment. Moisture content of the fat appeared to affect hydrolysis. The free fatty acid content of several foods prepared by deep-frying was also determined. Our recent observation that the free fatty acid content of the diet affected the severity of atherosclerosis in cholesterol-fed rabbits was the stimulus for these studies.