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Interaction of a Cationic Acrylate Polymer with Caseins: Biphasic Effect of Eudragit E100 on the Stability of Casein Micelles

Ausar, Salvador F., Bianco, Ismael D., Castagna, Leonardo F., Alasino, Roxana V., Beltramo, Dante M.
Journal of agricultural and food chemistry 2003 v.51 no.15 pp. 4417-4423
casein, electrostatic interactions, ionic strength, light scattering, micelles, skim milk
When whole or skim milk was incubated with the cationic acrylate polymer Eudragit E100, a biphasic effect on the stability of casein micelles was observed. A precipitation phase was observed at low polymer/casein ratios. Strikingly, a solubilization phase of the aggregates was observed when the ratios of polymer/casein were increased. Purified α(s)-, β-, and κ-caseins or dephosphorylated caseins were equally precipitated and resolubilized by the cationic polymer, indicating no special selectivity for a particular protein or phosphate residue for these events. An increase in the size of the aggregates as the optimum precipitating amount of Eudragit E100 was reached suggests a crossbridging of the micelles by the polymer. The inhibition of the precipitation phase by high ionic strength indicates that electrostatic interactions play a critical role in complex formation. Furthermore, a dramatic reduction in size of the protein colloidal particles upon solubilization of the aggregates was observed by dynamic light scattering, indicating a dissociation of the micellar structure. Taken together, the results indicate that at low oncentration Eudragit E100 may act as a precipitant of casein micelles, mainly by ionic interaction and at high concentration as an amphipathic agent, solubilizing casein micelles with a disruption of their internal structure.