Examination of whole milk powder by confocal laser scanning microscopy

Confocal laser scanning microscopy was used to examine components of whole milk powder. Powder was dispersed in a glycerol suspension containing a fat-soluble fluorescent dye which was excited by laser light to produce images of the fat at the surface of and inside the whole milk powder particle. Lactose crystals, produced in the milk prior to spray drying, were seen to be in the diamond-like, α-hydrate form. The surface coverage and the stability of a wetting agent sprayed on to the surface of whole milk powder particles were examined. The wetting agent was shown to be located as a thin surface layer that partly migrated into creases and folds on the particle surface during storage at 37°C.