Interaction of a cationic acrylate polymer with caseins: biphasic effect of Eudragit E100 on the stability of casein micelles

S.F. AUSAR; I.D. BIANCO; L.F. CASTAGNA; R.V. ALASINO; D.M. BELTRAMO

JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY

American Chemical Society

Año: 2003 vol. 57 p. 4417 - 4423

0021-8561

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 Rs-, â-, and -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 concentration 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.Rs-, â-, and -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 concentration 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.