One of the common and important off-flavors in milk is hydrolytic rancidity or
lipolyzed flavor. The rancidity results from hydrolytic cleavage of fatty acids from milk fat
by the enzyme lipase and their release as free acids. The release of these acids in milk, even
in very small amounts, imparts a bitter taste and a sharp, unpleasant aroma. The off-flavor
is often described as "goaty", "butyric", "soapy", and "bitter" The term "bitter", however, is
ambiguous because bitter flavors can occur from the result of protein breakdowns.
Nevertheless, both farm and dairy plant problems may lead to its development. Once an
objectionable level is reached, no processing technique will eliminate it.