THE SURFACE COVERAGE OF FAT ON FOOD POWDERS ANALYZED BY ESCA (ELECTRON-SPECTROSCOPY FOR CHEMICAL-ANALYSIS)

ESCA (electron spectroscopy for chemical analysis) was used to estimat e the fat coverage on different spray-dried food powder surfaces. The method presented here represents a new way of estimating the actual su rface coverage of fat on a food powder. The ESCA-method is illustrated with three different series of experiments. The results obtained with the ESCA-technique are combined with the results obtained from the co nventional free fat extraction technique for different spray-dried pow ders. In the first series, emulsions containing different ratios of pr otein to fat were spray-dried. An increase in the amount of fat in the emulsion gives an increased surface coverage of fat. Powders with a h igh fat content shows a high free fat level, indicating a continuous n etwork of fat inside the particles. Secondly, the effect of heat treat ment on the ability of bovine serum albumin to encapsulate fat has bee n investigated. The results show that albumin treated at high temperat ure encapsulates the fat less completely than the albumin treated at l ow temperature. Finally, emulsions containing oil phases with differen t melting points were spray-dried and analyzed. Powders with a high me lting fat show very well encapsulated fat with only a minor surface co verage of fat. Powders with a qualitatively different distribution of fat can be identified by comparing the surface coverage of fat estimat ed by ESCA with the free fat measurements.