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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.