Aggregation of Casein Micelles by Interactions with Chitosans: A Study by Monte Carlo Simulations.

C.F. NARAMBUENA, S.F. AUSAR, I.D. BIANCO, D.M. BELTRAMO AND E.P.M. LEIVA.

JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY

AMERICAN CHEMICAL SOCIETY

Año: 2005 vol. 53 p. 459 - 463

0021-8561

Recently it was found that the addition of chitosan, a cationic polymer, to whole or skim milk produces destabilization and coagulation of casein micelles which take place without causing changes in the milk pH, or in the stability of most of the whey proteins (Ausar S.F. et al. Journal of Dairy Sciece 2001, 84, 361-369). In the present work we employ Monte Carlo simulations to show that the phase separation of casein micelles induced by chitosan can be explained by a depletion mechanism, where an effective attraction between the casein micelles is induced by the presence of chitosan molecules.This interaction is described on the basis of Vrij´s model, where the depletion of polymer from the gap between neighbouring casein micelles originates an effective attractive interaction that leads to a phase transition. This model, that considers volume restriction effects, is able to account for several qualitative and even quantitative aspects of the experimental data for the coagulation of casein by chitosans.