Influence of low methoxyl pectin on the physicochemical properties of sodium caseinate-stabilized emulsions

Two strategies of emulsion preparation, stabilization by sodium caseinate (CAS)/low methoxyl pectin (LMP) complexes formed in advance, and stabilization by the layer-by-layer (LBL) method, were compared. In aqueous solution, at a constant CAS concentration (5 g/L), the gradual addition of LMP resulted in an increase in turbidity of the solution caused by the increasing formation of insoluble complexes. The zeta potential change showed that the interactions are mainly due to an electrostatic mechanism. The spectrofluorometric studies as well as the spectroscopic analysis in the UV-visible region have shown that the interactions with LMP caused a change in the secondary and tertiary structures of the protein. Then, these complexes were used for stabilizing oil/water emulsions. The emulsions stabilized by complexes formed in advance and LBL method were characterized by measuring zeta potential, dynamic viscosity, serum index, and particle size distribution. The results showed that, at low LMP concentrations, complexes-stabilized emulsions were more stable than LBL-stabilized ones, while at high LMP concentrations, LBL-stabilized emulsions showed better stability. Practical applicationsThese results would be useful during the development of encapsulation systems having hybrid interfaces in order to better control the release of hydrophobic active molecules like essential oils. These molecules have various benefits like antioxidant and antimicrobial activities, which could be exploited for food biopreservation. One of the major problems for application in food preservation of these active molecules is their great sensitivity to the environmental stress (temperature, pH...), their low water-solubility, their interactions with food components, and their pronounced odor and flavor. The encapsulation of these molecules in the developed emulsions containing the proper concentration of LMP could be a suitable solution to protect and release these lipophilic molecules in foods.