The quality of milk powders is markedly affected by the composition and properties of the milk, the manufacturing procedures, thermal processing during manufacture and, in particular, the drying technique itself. A variety of physico-chemical analytical methods, including scanning electron microscopy, has been used to obtain information on the effects of the various factors on the microstructure of the milk powders. Roller-drying, which has recently lost its commercial importance, produces a sheet of dried milk that is powdered in a hammer mill. The resulting powder consists of compact particles with sharp edges. Powders obtained by spray-drying are in the form of more or less regular globules which may have their surface convoluted to a varying extent. Inside, the particles are porous. Lactose present in the particles is in an amorphous glass form. In instant milk powders, the powder particles are agglomerated and lactose is partly converted into microcrystalline form.
Caric, Marijana and Kalab, Miloslav
"Effects of Drying Techniques on Milk Powders Quality and Microstructure: A Review,"
2, Article 9.
Available at: http://digitalcommons.usu.edu/foodmicrostructure/vol6/iss2/9