title: Interest of energy dispersive X-ray microanalysis to characterize the surface composition of milk powder particles.
abstract: Energy dispersive X-ray (EDX) is a technique rarely used for organic powders. Nevertheless, this technique is of great interest in the characterization of milk particle surface. In order to validate the method, the EDX technique was tested on pure milk components, on model powders composed of different ratio of lactose/whey proteins and on whole milk powders presenting or not free fat at the surface. For all these powders, satisfactory results were obtained with correct experimental atomic percentages in comparison with expected theoretical percentages. The technique was then applied to skimmed and whole milk powders sieved in 4 fractions. The surface and the core (cut particle) were analyzed by EDX and compared. A relationship between the particle size and the surface composition was observed. X-ray photoelectron spectroscopy (XPS) often used to characterize milk powder surface, however no differences were observed between surface and core composition using this method. The depth of analysis by EDX is far more significant (1 μm) in comparison to that of the XPS (5 nm); hence it was concluded that the analysis of cut particle by EDX was not interesting since too close to the results obtained at the surface. Finally, the technique was coupled with XPS and successful hypothesis concerning composition gradients were done.
authors.affiliation: Université de Lorraine, LIBio (Laboratoire d'Ingénierie des Biomolécules), 2 Avenue de la forêt de Haye, TSA 40602, 54518 Vandœuvre-lès-Nancy Cedex, France; Université de Toulouse, Mines Albi, CNRS UMR 5302, Centre RAPSODEE, Campus Jarlard, 81013 Albi cedex 09, France.
authors.forename: I
authors.initials: I
authors.lastname: Murrieta-Pazos
authors.affiliation: Université de Toulouse, Mines Albi, CNRS UMR 5302, Centre RAPSODEE, Campus Jarlard, 81013 Albi cedex 09, France.
authors.forename: L
authors.initials: L
authors.lastname: Galet
authors.affiliation: Université de Toulouse, Mines Albi, CNRS UMR 5302, Centre RAPSODEE, Campus Jarlard, 81013 Albi cedex 09, France.
authors.forename: C
authors.initials: C
authors.lastname: Rolland
authors.affiliation: Université de Lorraine, LIBio (Laboratoire d'Ingénierie des Biomolécules), 2 Avenue de la forêt de Haye, TSA 40602, 54518 Vandœuvre-lès-Nancy Cedex, France.
authors.forename: J
authors.initials: J
authors.lastname: Scher
authors.affiliation: Université de Lorraine, LIBio (Laboratoire d'Ingénierie des Biomolécules), 2 Avenue de la forêt de Haye, TSA 40602, 54518 Vandœuvre-lès-Nancy Cedex, France. Electronic address: claire.gaiani@univ-lorraine.fr.
authors.forename: C
authors.initials: C
authors.lastname: Gaiani
mesh_terms: D000818:Animals; D004577:Electron Probe Microanalysis; D008855:Microscopy, Electron, Scanning; D008892:Milk / Q000737:chemistry*; D010316:Particle Size; D056951:Photoelectron Spectroscopy; D011208:Powders; D013052:Spectrometry, X-Ray Emission; D013499:Surface Properties
chemical_list: D011208:Powders
keywords: Composition gradients; Dairy powders; Energy dispersive X-ray technique; Surface composition