Isolation and composition of milk fat globule membrane material

Abstract

SummaryMilk fat globule membrane (MFGM) material was isolated from commercial pasteurized milks and pasteurized creams using a procedure specifically adapted for these products (McPhersonet al.1984a). Pasteurized cream membranes contained higher lipid levels while pasteurized milk membrane material had lower lipid contents than fresh raw MFGM. Electrophoretic analysis showed that membrane material from both commercial products contained, in addition to native MFGM polypeptides, significant amounts of β-lactoglobulin with lower levels of caseins and other skim-milk components. The incorporation of β-lactoglobulin was more pronounced in pasteurized cream membranes. Examination of the lipoprotein complexes present in these membrane preparations by linear sucrose density gradient centrifugation showed that pasteurized milk membrane material had a similar profile to fresh raw MFGM except that preferential binding of skim-milk components was found in some of the lipoprotein fractions. Pasteurized cream membranes showed considerably different density gradient patterns with only 2 lipoprotein fractions present, of which the major one was a low density complex.