Membrane phospholipids and sterols in microfiltered milk fat globules

Native milk fat globules of various mean diameters, ranging from d(43) = 2.3 mu m to 8.0 mu m, were obtained using microfiltration of raw whole milk. After milk fat globule washing, the milk fat globule membrane (MFGM) was separated by manual churning. After total lipid extraction and separation of polar lipids, their phospholipid (PL) and sterol composition was measured using thin-layer chromatography, methyl ester analyses by gas chromatography, and gas chromatography coupled to mass spectrometry. The main PL species were phosphaticlylethanolamine, phosphatidylcholine and sphingomyelin. The respective fatty acid composition of each PL species was measured. Many different minor bioactive sterols were detected in the MFGM, e.g. lanosterol, lathosterol, desmosterol, stigmasterol and P-sitosterol. No significant differences in the PL and sterol profile were found between MFGM extracted from small and large milk fat globule fractions.