Characteristics of Lipolytic System in Goat Milk

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Abstract
The caprine milk lipolytic system was characterized to explain the higher correlation in the goat, as opposed to the cow, between lipoprotein lipase activity and spontaneous lipolysis. Goat milk lipoprotein lipase was distributed primarily in cream (46%) and serum (46%), but little activity was in caseins (8%). The quantitative distribution in cow milk lipoprotein lipase was different (6, 17 and 78%, respectively). This probably reflected species differences in properties of milk caseins and fat globules. Spontaneous lipolysis in goat milk was activated as in the cow by addition of blood serum, but only if the total lipoprotein lipase activity of goat milk was higher than 4 .mu.eq free fatty acids/h per ml. Although heparin had no effect on goat milk lipolysis, it affected cow milk lipolysis and stimulated goat and cow milk lipoprotein lipase activity on an artificial substrate in vitro. Some heated (60.degree. C for 30 min) normal milks showed an inhibitory effect on lipolysis in fresh susceptible goat milks. This inhibitory effect was recovered in caseins and primarily in serum and proteose-peptones, but not in cream. Heated susceptible milks did not appear to have had any activating effect on lipolysis in fresh normal goat milks. Possible effects on farm bulk milk also were discussed.