Rancidity and Degradation of Fats and Oils

In fats and oils, unsaturated fatty acids are attached to glycerol to form triglycerides. Typically, you only see these unsaturated fatty acids in their “free form” (that is, unattached to the glycerol) when some kind of degradation of the fat or oil occurs, such as oxidation. Oxidation is a process in which oxygen reacts with the unsaturated fatty acids in a fat or oil. Unlike hydrogenation, which is used to increase the stability of a fat or oil, oxidation does the opposite, creating off-flavors such as rancidity, which is how you know degradation has occurred.