a1 Institute de Productos Lácteos, Arganda del Rey, Madrid, Spain
a2 Sectión de Bioquímica de Membranas, Velázquez, 144, Madrid-6, Spain
The morphology, protein and glycoprotein composition, amino-acid analysis, phospholipid and carbohydrate contents and 3 phosphoesterase activities of the milk-fat globule membranes were studied in 4 cows during their whole period of lactation. No differences were found in the morphology and the overall chemical composition. However, glycoprotein composition varied with the cow and, for each cow, with the stage of lactation. The differences were more marked for membranes obtained from colostrum. Acid phosphomonoesterase was practically unchanged during the whole period of lactation, while alkaline phosphomonoesterase and phosphodiesterase increased as lactation proceeded.
(Received November 23 1976)