title: Surface composition of dairy powders observed by X-ray photoelectron spectroscopy and effects on their rehydration properties.
abstract: The surface composition of three dairy powders was investigated by X-ray photoelectron spectroscopy. These spray-dried casein powders were more or less enriched in hygroscopic material (lactose and/or minerals). The principal limitation of these high protein content powders is their poor rehydration ability. Consequently, information about surface composition is required in order to get a better understanding of rehydration behaviour (i.e. wetting time and time of rehydration). The obtained results indicate that the surface of the three powders was dominated by proteins. Lactose and minerals are marginal compounds at the surface whereas the surface coverage of fat was over represented. A correlation between the lactose surface content and the wetting time of the powders was found, but no relationship with the surface fat. Moreover, as the surface is partly depleted in minerals and lactose, it is concluded that these compounds are principally located in the bulk of the particle. Therefore this observation could be related with a wetting time of the powders only slightly affected by the addition of hygroscopic material whereas the time of rehydration was strongly improved; powder wetting being more affected by the surface composition whereas powder dispersion being more influenced by the powder bulk composition.
authors.affiliation: Laboratoire de Sciences et Génie Alimentaires, LSGA, 2 avenue de la Forêt de Haye, B.P. 172, 54505 Vandoeuvre Lès Nancy, France.
authors.forename: C
authors.initials: C
authors.lastname: Gaiani
authors.forename: J J
authors.initials: JJ
authors.lastname: Ehrhardt
authors.forename: J
authors.initials: J
authors.lastname: Scher
authors.forename: J
authors.initials: J
authors.lastname: Hardy
authors.forename: S
authors.initials: S
authors.lastname: Desobry
authors.forename: S
authors.initials: S
authors.lastname: Banon
mesh_terms: D002364:Caseins / Q000737:chemistry*; D004583:Electrons; D007785:Lactose / Q000737:chemistry; D008903:Minerals / Q000737:chemistry; D010316:Particle Size; D011208:Powders / Q000737:chemistry; D012680:Sensitivity and Specificity; D013057:Spectrum Analysis; D013499:Surface Properties; D013997:Time Factors; D014867:Water / Q000737:chemistry; D017155:Wettability; D014965:X-Rays
chemical_list: D002364:Caseins; D008903:Minerals; D011208:Powders; D014867:Water; D007785:Lactose