Insights into the Stability and Lipid Oxidation of Water-in-Oil High Internal Phase Emulsions: Roles of the Concentration of the Emulsifier, Aqueous Phase, and NaCl.

Water-in-Oil high internal phase emulsions (W/O HIPEs) have great potential in developing novel healthy food products. However, the high content of the aqueous phase poses great risks in physical stability and lipid oxidation. This study aimed to understand the relationship between physical stability and lipid oxidation of W/O HIPEs, focusing on the roles of emulsifiers, aqueous phase volume, and NaCl concentration. The findings revealed that increasing the polyglycerol polyricinoleate (PGPR) concentration (10 wt%) significantly enhanced physical stability and slowed lipid oxidation at various temperatures. W/O emulsions with varying aqueous phase volumes (30-80%) maintained good physical stability; however, a higher aqueous phase volume significantly accelerated lipid oxidation. Furthermore, the inclusion of NaCl (10-300 mM) improved the physical stability of W/O HIPEs but also accelerated lipid oxidation. Notably, W/O HIPEs with 50 mM NaCl showed both optimal physical and oxidative stability. Additionally, based on the fitting equation of the primary oxidation products, it was predicted that the oxidation reaction of the W/O emulsion followed a zero-order oxidation kinetics model. By altering the structure of the emulsion system, the physical stability and lipid oxidation stability of the emulsion could be regulated, thereby extending the storage time of food products. Overall, these findings emphasized the critical role of interfacial properties in lipid oxidation, providing new insights for optimizing food formulations to enhance long-term stability.