Synergistic effects of phosphatidylcholine and cholesterol on lipid droplet interfacial structure and in vitro digestibility of simulated breast milk fat emulsion.

The unique digestive requirements of infants highlight the importance of optimizing the interfacial properties of simulated breast milk fat emulsions in infant formula. This study aimed to investigate the effects of cholesterol and phosphatidylcholine (PC) on the interfacial composition, physicochemical properties, and in vitro digestion behavior of a simulated breast milk fat emulsion. PC and cholesterol addition significantly increased interfacial cholesterol and phospholipid contents while decreasing interfacial protein adsorption. Among the tested formulations, the PC to cholesterol ratios of 1:1 showed the smallest particle size (639 nm), the highest absolute zeta potential, and the lowest Turbiscan Stability Index, indicating improved physicochemical stability. Fluorescence microscopy suggested a more uniform phospholipid-related fluorescence distribution in the 0.5:1 and 1:1 groups, which was consistent with improved interfacial organization. During in vitro digestion, the 1:1 group exhibited the highest apparent free fatty acid release in the intestinal phase, whereas the control group showed the lowest release. GC-MS analysis further revealed differences in the relative fatty acid composition of the released FFAs among treatments. Overall, an appropriate PC -to -cholesterol ratio, particularly 1:1, improved the interfacial properties, stability, and digestive performance of the simulated breast milk fat emulsion.