Lipid domains in the milk fat globule membrane: the dynamics investigated in situ in milk in relation to temperature and time

Abstract

International audienceMilk is an emulsion of fat droplets stabilized by a biological membrane called the milk fat globule membrane (MFGM; Figure 1). The MFGM is mainly composed of polar lipids that have different melting temperatures (Tm), cholesterol, glycoproteins, and enzymes. The microstructure of the MFGM depends on the packing of polar lipids in the outer bilayer of the membrane that can lead to phase separation with formation of ordered domains (Figure 2). Milk is usually submitted to changes in temperature e.g. storage (4-7°C), churning (10-12°C) and heat treatments (e.g. pasteurization). Do these temperature variations and thermal history of milk affect the packing of polar lipids in the plane of the MFGM ? Experiments were performed by confocal laser scanning microscopy (CLSM) under temperature controlled conditions, using the head-labelled phospholipid fluorescent probe Rh-DOPE. Only the fluid phase of MFGM was labelled