Globule milk fat: Secretion, composition, function and variation factors

Nutritional and technological properties of milk fat are affected by fat globule size and composition. These properties can be modified by animal factors and/or animal nutrition. The objective of this review was to describe the biochemical and physiological mechanisms of milk fat synthesis and secretion and the animal and nutritional factors which modify these mechanisms, the milk fat globule size and composition. In a first part, the presumed mechanisms of milk fat globule secretion are presented in order to specify the milk fat globule characteristics (average size, composition and structure of milk fat globule membrane and core). In a second part, technological, organoleptic and nutritional properties of milk fat globules are described. In a third part, this review develops the influence of animal and nutritional factors on milk fat globule size and milk fat globule membrane composition. This review exhibits the lack of knowledge in the co-regulation of milk fat synthesis and secretion. Technological properties of milk fat globules are mainly modified by their size and nutritional properties by the composition of their membrane. Breed, parity and lactation stage have little impact on milk fat globule size compared to the individual variability. The nature, form and level of forages and concentrates in the diet also modify milk fat globule properties.