Surface characterization of four industrial spray-dried dairy powders in relation to chemical composition, structure and wetting property

The surface composition of powders is expected to play an important role during its end use. Understanding the mechanism of the powder surface formation in terms of the compositional aspect and the ability to control the surface composition will be highly useful in milk powder quality improvement and, new product development. For a preliminary study, the surface compositions of four industrial spray-dried dairy powders (skim milk powder, whole milk powder, cream powder and whey protein concentrate) manufactured for consumer use, were studied by means of electron spectroscopy for chemical analysis (ESCA). It was found that all the powders have relatively high surface fat coverage. In order to verify these results and to demonstrate the usefulness of ESCA in analysing the surface composition of dairy powders, fresh powders and fat extracted powders were subjected to the following experiments: measurement of powder surface composition, surface structure studies, fat localization studies, wetting test and measurements of surface oxygen uptake during storage. The results obtained indicate that the ESCA measurements are very reliable and the surface composition of the industrial spray-dried dairy powders estimated by ESCA is also expected to be reliable. In addition, the results showed fat globules encapsulated by protein or proteins are preferentially located underneath the surface fat. (C) 2002 Elsevier Science B.V. All rights reserved.