Effect of calcium concentration on the structure of casein micelles in thin films.
The structure of thin casein films prepared with spin-coating is investigated as a function of the calcium concentration. Grazing incidence small-angle x-ray scattering and atomic force microscopy are used to probe the micelle structure. For comparison, the corresponding casein solutions are investigated with dynamic light-scattering experiments. In the thin films with added calcium three types of casein structures, aggregates, micelles, and mini-micelles, are observed in coexistence with atomic force microscopy and grazing incidence small-angle x-ray scattering. With increasing calcium concentration, the size of the aggregates strongly increases, while the size of micelles slightly decreases and the size of the mini-micelles increases. This effect is explained in the framework of the particle-stabilizing properties of the hairy layer of kappa-casein surrounding the casein micelles.
Müller-Buschbaum
P
P
Physik-Department, Technische Universität München, Garching, Germany. muellerb@ph.tum.de
Gebhardt
R
R
Roth
S V
SV
Metwalli
E
E
Doster
W
W
D000818:Animals; D002118:Calcium / Q000737:chemistry* / Q000494:pharmacology; D002364:Caseins / Q000737:chemistry* / Q000187:drug effects / Q000302:isolation & purification / Q000648:ultrastructure; D008027:Light; D008823:Micelles; D008853:Microscopy; D018625:Microscopy, Atomic Force; D008892:Milk / Q000737:chemistry; D011485:Protein Binding; D012542:Scattering, Radiation; D012996:Solutions; D014462:Ultrafiltration; D014961:X-Ray Diffraction
D002364:Caseins; D008823:Micelles; D012996:Solutions; D002118:Calcium