Effects of Proteins and Mineral Ions on the Physicochemical Properties of 1,3-Dioleoyl-2-Palmitoylglycerol Emulsion to Mimic a Liquid Infant Formula

Proteins and minerals in infant formula not only serve as nutrients, but also have important effects on the physical and chemical stability of emulsions. In this study, calcium carbonate (0 or 9.08 mM) and potassium chloride (0 or 15.96 mM), as representatives of divalent and monovalent minerals, were added to 1,3-dioleoyl-2-palmitoylglycerol (OPO) emulsions in different ratios (10:0, 9:1, 6:4, 5:5, and 0:10) of whey protein isolate (WPI) and sodium caseinate (CN). The influence of proteins and minerals on emulsion stability was investigated by analyzing particle size, zeta potential, creaming index, rheological properties, storage stability, and lipid oxidation. 1,3-dioleoyl-2-palmitoylglycerol (OPO) emulsions could be destabilized by adding Ca(2+), as shown by the increase in particle size index, creaming index, and the decrease in zeta potential magnitude. Divalent ions could affect the electrostatic interactions between lipid droplets and the interactive effects of ion surface adsorption. In addition, the effect of different protein ratios on the physical stability of emulsions was not significant under the same ion-type conditions. In terms of chemical stability, higher oxidized values were found in emulsions stabilized with only CN than in those containing WPI. Our study showed that protein ratios and minerals played an important role in the stability of OPO emulsions, which might provide a reference for the development and utilization of liquid infant formula.