pH-induced cold gelation of caseinglycomacropeptide emulsions

Caseinglycomacropeptide (CMP) is a valuable peptide for its bioactive as well as for its technological properties. One of the more relevant properties of this peptide is its ability to self-assemble in solution by decreasing the pH below 4.5, leading to gel formation. The objective of present work was to characterize CMP and CMP/Co-emulsifiers based oil/water emulsions and to evaluate if these emulsions may undergo a pH-dependent gelation. In addition, the stability of the gelled CMP emulsion to pH changes was evaluated. The droplet size of the emulsions was determined before and after the reversal of gelation, to evaluate the degree of destabilization. Additionally, interfacial studies of CMP and CMP/co-emulsifier (lecithin (LEC), arabic gum (AG), gelatin (GEL) and sodium caseinate (NaCas)) were performed in a drop tensiometer to understand the emulsions behavior. It was not possible to form a stable CMP emulsion over time at pH 6.5. By lowering the pH, the gelation of CMP emulsion was achieved; however, during the acidification necessary to promote gelation, the emulsion partially coalesced. In the competitive adsorption between CMP and the co-emulsifiers, the interfacial pressure was controlled by the component that exhibits higher interfacial activity. CMP dominated the interfacial pressure in mixtures with GEL, LEC and AG, while in CMP/NaCas mixture it was controlled by NaCas. Among the co-emulsifiers studied, NaCas and LEC improved the stability of CMP emulsion over time; however, none of the co-emulsifiers studied in the present work could improve the stability of CMP emulsions against pH changes.