Structure of the Milk Fat Globule Membrane: New Scientific Advances Revealing the Role of Sphingomyelin in Topographical and Mechanical Heterogeneities

Abstract

The milk fat globule membrane (MFGM) is a unique interface rich in polar lipids, cholesterol and proteins, bringing specific functions in the gastro-intestinal tract. In this book chapter, new scientific advances about the structure and mechanical properties of the MFGM are reviewed, in relation with the specific composition of this biological membrane and the physical properties of milk polar lipids that are mainly due to the high amount of sphingomyelin (SM). The MFGM is a patchwork of polar lipids with lateral phase separation of high melting temperature Tm saturated polar lipids such as milk-SM (Tm=34.3°C) leading to the formation of ordered microdomains that are higher and more rigid than the surrounding fluid matrix composed of low Tm unsaturated polar lipids in which the proteins are embeded. The microdomains are reactive to thermal kinetics and can diffuse in the plane of the MFGM. Attractive interactions between SM and cholesterol are involved in the formation of complexes in a wide range of temperatures (4 to 60°C). Structural and mechanical heterogeneities in the MFGM and in milk polar lipid assemblies have been evidenced. These recent information will contribute in a better undertanding of MFGM functions and open perspectives in the valorization of milk polar lipids and MFGM-rich ingredients for food and nutritional applications.