Enhancing the physical stability and bioaccessibility of curcumin emulsions through the interaction of whey protein isolate and soybean lecithin

Inspired by the milk fat globule membrane composition, we investigated the interaction between whey protein isolate (WPI) and soybean lecithin (SL) at various mass ratios (10:0, 10:1, 10:2, 10:5, 10:10, and 10:15) and their effects on curcumin emulsions. Our results demonstrated that SL interacted with WPI through hydrophobic interactions and hydrogen bond restructuring. The WPI–SL complex effectively enveloped oil droplets, resembling natural milk fat globules. Notably, the 10:10 sample exhibited the smallest droplet size (217.33 nm), lowest polydispersity index (0.202), and lowest zeta potential (−43.56 mV). After heat treatment at 90 °C for 1 h, the 10:10 sample exhibited the highest thermal stability, and its polydispersity index (0.236) was significantly lower than at other mass ratio (0.332–0.268). During in vitro digestion, emulsions stabilized by the WPI–SL complex exhibited less oil droplet aggregation, resulting in enhanced curcumin bioaccessibility (58.73–66.32%) compared to pure WPI-stabilized emulsions (57.45%). These findings signify the potential of WPI–SL complexes in constructing effective delivery systems mimicking natural fat globule structures, thereby improving curcumin bioavailability. The systematic investigation of different WPI–SL mass ratios in this study provides valuable insights for optimizing emulsifier compositions in the food industry.