Lipid Composition of the Fat Globule Membrane of Human and Bovine Milk

Fat globule membrane material of human and cow's milk was isolated from the creams by successive ultracentrifugations. The polar and nonpolar lipids were then extracted and their constituents identified. Lipidic fractions of the membrane of both milks contained high-melting triglycerides and a large amount of polar lipids and intermediary compounds of their biosynthesis, such as phospholipids, sterols, alkanes and acyclic terpenes. Human milk contained more unsaponifiable matter and organic phosphorus, and slightly less triglyceride than cow's milk. The fatty acid composition of the triglycerides of both milks was similar, except for the remarkably small amount of arachidic acid and for the large amount of linoleic acid in human milk as compared to cow's milk. In both milks, the total amount of short-chain fatty acids was higher in the bulk of fat than in the membrane. Other differences in the lipids of human and cow's milk were also evidenced: these concerned mainly the degree of unsaturation, the positional distribution of fatty acids, cholesterol and 7-dehydrocholesterol content, the amount and type of phospholipids as well as their fatty acid distribution.