Buffalo milk fat globules and their biological membrane: in situ structural investigations

- The structure of buffalo milk fat globule membrane (MFGM) was investigated in-situ in milk.
- Glycosylated molecules and polar lipids are distributed heterogeneously in the MFGM.
- Lipid domains were formed by the segregation of high Tm lipids and cholesterol.
- Lipid domains were both circular and non-circular in shape.
- Cytoplasmic crescents were occasionally attached to the buffalo fat globules.

Milk fat globules and their surrounding biological membrane (the MFGM) are not well understood despite the importance of these milk components in human nutrition and the role of fat globules in determining the properties of dairy products. The objectives of this study were to investigate these unique colloidal assemblies and the microstructure of the MFGM in buffalo milk, which is the second largest global source of dairy products. In-situ structural investigations were performed at room temperature using confocal microscopy with multiple fluorescent probes (Nile Red, Rh-DOPE, the lectin WGA-488). Microscopic observations showed cytoplasmic crescents around fat globules and the heterogeneous distribution of glycosylated molecules and polar lipids with the occurrence of lipid domains. The lipid domains in the buffalo MFGM appear to form by the segregation of lipids with a high phase transition temperature (e.g. sphingomyelin and saturated phosphatidylcholine molecular species) and cholesterol resulting in a gel phase or a Lo phase forming circular domains. The structure of the buffalo MFGM results from a non-random mixing of components, consistent with observations for other species. Structural heterogeneities of the MFGM could affect the processability of buffalo fat globules and the bioavailability of milk lipids.

Lipid domains in the biological membrane surrounding buffalo milk fat globules.288