Abstract: In this study, yak ghee was prepared from yak milk fat, obtained by centrifugal separation, and washed yak milk fat, separately, and the distribution patterns of milk fat globule membrane (MFGM) components in the aqueous phase, buttermilk, and whey during ghee processing were systematically analyzed. Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE) was used to analyze protein composition, and solid-phase extraction, thin-layer chromatography, and gas chromatography were combined to comprehensively analyze the composition and distribution characteristics of lipids. The results showed that fat washing enriched the characteristic proteins of MFGM, significantly decreased the contents of polar lipids in yak milk fat and buttermilk (P < 0.05), but had no significant effect on the content of polar lipids in whey. The lipids in buttermilk and whey were different in terms of polar lipid/fat ratio, phospholipid composition (phosphatidylethanolamine (PE) was enriched in buttermilk, while sphingomyelin (SM) was enriched in whey), and unsaturation degree. This study revealed that the differential distribution of MFGM components between buttermilk and whey was mainly related to the physicochemical properties of fat globules.

Key words: milk fat globule membrane; ghee whey; buttermilk; proteins; lipids; fat washing