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

Abstract

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 alpha(s)-, beta-, and kappa-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.

Amphipathic and Membrane‐Destabilizing Properties of the Cationic Acrylate Polymer Eudragit® E100

“…Total protein concentration in human plasma from normal volunteers was evaluated by Biuret or by direct absorbance at 280 nm as previously described 11. The activity of glutamic oxalacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), lactate dehydrogenase (LDH) and alkaline phosphatase (AP) were measured by commercially available enzymatic methods (Wiener Lab., Rosario, Argentina).…”

“…In a previous study, we described that E100 displays a biphasic coagulating‐resolubilizing effect of caseins and milk fat from bovine milk 11. It was also shown that, from the various intermolecular forces that could be involved in complex formation, both electrostatic and hydrophobic interactions play a critical role between E100 and caseins 11.…”

“…In a previous study, we described that E100 displays a biphasic coagulating‐resolubilizing effect of caseins and milk fat from bovine milk 11. It was also shown that, from the various intermolecular forces that could be involved in complex formation, both electrostatic and hydrophobic interactions play a critical role between E100 and caseins 11. This was strikingly different from the mechanism of chitosan‐casein complex formation, where, despite the involvement of a combination of hydrophobic and electrostatic interactions in the coagulation process observed, no resolubilization of the aggregates was observed with an excess of chitosan 12.…”

Interaction between casein and sodium dodecyl sulfate

“…It must be emphasized that, in many earlier studies [3][4][5][6][7], much interest has only been focused on the interaction between casein micelles and additives, but no attention has been paid to the interaction between casein monomers (or submicelles) and additives because of the high casein concentration. Here, the ITC results can monitor the interaction of SDS with casein micelles or monomers, respectively.…”

“…However, the form-function relationship is not static in nature. Many studies have shown that solutes and solvents can significantly alter the behavior and overall performance of casein [3][4][5][6][7]. In commercial products such as casein, mixed systems with surfactants are generally employed to obtain better performance for the products.…”