Relationship of Fat Acidity to Rancidity in Homogenized Raw Milk

The action of milk lipase on butter fat is generally believed to produce at least two detectable changes : first, the production of free fatty acids, and second, the production of rancid or rancid-like flavors. The production of the rancid flavor is attributed to free butyric acid and other lower fatty acids such as capric, caprylic, and caproic. Furthermore, the appearance of the rancid flavor is expected whenever milk fat undergoes lipolysis, indicating that the glycerides of the lower fatty acids are always attacked by lipase under normal conditions. Some efforts have been made to correlate the extent of fat splitting with rancid flavor development (1, 5, 7), but information on this relationship is byno means complete nor has it been applied to conditions in which the lipase activity is accelerated by homogenization.