Milk contains different types of colloidal or coarsely dispersed particles, such as casein micelles, membrane fragments, fat globules and cells. The fat globules are composed of subpopulations of differently sized particles. In contrast to COW 1S milk, the overall average diameter (dys), increases with advancing lactation from about 1.8 ~min colostrum to 4.0 ~min mature milk. Membrane materials originating from the milk fat globule membrane, plasma membrane, secretory vesicles and other sources can be found in milk serum. These particles have also been called lipoprotein particles. Their size ranges from about 10 - 400 nm. New results concerning the structure of human milk casein particles show that their average size is considerably smaller than in cows milk and that their average diameter tends t~ increase with advancing lactation. dvs in human milk ranges from about 11 -55 nm, in COW 1 S milk from approximately 90 - 100 nm. The structure of the acidified or renneted human milk differs significantly from that of equally treated cow 1s milk. In human milk there is no coagulation at all or the coagulum appears much looser than in bovine milk. The different types of cells in human milk have diameters in the range of about 8- 40 ~m. A sharp decrease in the total cell number from about 3. 106/ml in colostrum to 104 - 105/ml in mature milk can usually be observed. The relative amount of each type of cell varies in the course of lactation. The epithelial cells, typically 15 - 20 ~m in diameter, become the predominant type after 2 - 3 months.
Ruegg, M. and Blanc, B.
"Structure and Properties of the Particulate Constituents of Human Milk. A Review.,"
Food Structure: Vol. 1
, Article 4.
Available at: http://digitalcommons.usu.edu/foodmicrostructure/vol1/iss1/4