Caseinglycomacropeptide and polysorbate interactions allow the design of smart gelled emulsions

There is a growing interest in the development and use of smart materials. These materials are able to detect stimuli from their environment, for example, temperature, light, pH and to react in a useful, reliable and reproducible way. Caseinglycomacropeptide (CMP) is a valuable peptide for its bioactive and technological properties. One of the most relevant properties of this peptide is its ability to self-assemble in solution by lowering the pH below 4.5, which leads to the formation of a gel. The objective of the present work was to evaluate the ability of Tween 80 (Tw) to stabilize CMP emulsions over time and upon pH-dependent gelation in order to design smart gelled emulsions that could protect bioactive compounds. The gelation of emulsions was performed by decreasing pH to 2 and 3, and the gel time was determined. After 24 h the gelled emulsions were diluted in buffer to pH 6.5 to reverse to the liquid state. The droplet size of the emulsions before and after the gel reversibility experiment was determined. Also, the stability of the emulsions was evaluated over time. The interfacial properties of CMP, Tw and CMP/Tw were determined in a drop tensiometer in order to elucidate the emulsions behavior. The combination of CMP and Tw promoted the formation of stable gelled emulsions which were able to keep the initial droplet size after the reversion of the gelation. The formation of a complex between CMP and Tw occurring in the bulk would adsorb at the oil/water interface leading to stable emulsions. A synergistic interaction between both emulsifiers appears as the basis of this improvement in which Tw would contribute to steric stabilization of oil droplets, hindering the coalescence when decreasing pH.