Deterioration of fats, or rancidity, constitutes one of the most important technical problems in the food industries.
All the chemical reactions involved can be explained on the basis of the ester linkage and the nature of fatty acids glycerides.
Deterioration occurs though hydrolysis of the ester linkage by lipase and moisture (hydrolytic rancidity); through the auto-oxidation of unsaturated fatty acids glycerides in atmospheric oxygen (oxidative rancidity); through the enzymatic oxidation of unsaturated fatty acids glycerides (lipoxidase rancidity); or through the enzymatic oxidation of certain saturated fatty acids glycerides (ketone rancidity).
In hydrolytic rancidity the off flavor is due to the hydrolysis of a fat with the liberation of free fatty acids. Hydrolytic rancidity is extremely noticeable in fats such as butter because the volatile fatty acids released have a disagreeable odor and taste.
In contrast, hydrolytic changes in fats that contain a few volatile fatty acids are not accompanied by a bad odor and taste.
Deterioration of fats – Hydrolytic Rancidity
