Structural and functional enhancement of K2CO3-modified Okara insoluble dietary fiber for Pickering emulsion emulsification and digestion

Okara is a high-dietary-fiber byproduct of soybean processing with low utilization rates. Its insoluble dietary fiber (IDF) possesses significant nutritional value, yet its natural dense structure and limited interfacial activity constrain its application in food systems. To enhance its functionality, this study modified IDF using food-grade K 2 CO 3 to improve its structural and interfacial properties. The interfacial assembly behavior and stabilization mechanism of the modified fiber (M-IDF) in Pickering emulsions were investigated. Results showed that K 2 CO 3 treatment altered IDF's microstructure, reducing crystallinity to 17.32%. and significantly increased the zeta potential of M-IDF (−20.83 mV), thereby improving its water retention capacity, oil adsorption ability, and wetting properties. Consequently, M-IDF Pickering emulsions constructed with a 20% oil phase formed smaller, better-dispersed droplet structures and exhibited higher emulsifying activity and emulsion stability. Simulated gastrointestinal digestion experiments further demonstrated that the dense particle layer formed by M-IDF at the lipid droplet interface effectively inhibits droplet aggregation and lipase adsorption. This resulted in a free fatty acid (FFA) release rate of only 53.07% at 120 min, showcasing excellent lipid sustained-release capability. This research significantly enhances the structural and interfacial functionality of Okara IDF, positioning it as a promising natural solid emulsifier. It also provides a novel pathway for developing stable emulsified foods, fat-controlled foods, and functional delivery systems.