Citric Acid-Modified Sweet Potato Residue Insoluble Dietary Fiber as a Stabilizer for Pickering Emulsions

Sweet potato residue, a high-yield fibrous by-product generated during starch extraction processing, is abundant in insoluble dietary fiber (IDF) yet remains severely underutilized owing to its inherent limited functional characteristics. In this work, we adopted citric acid (CA) at gradient concentrations to modify the IDF extracted from sweet potato residue, and systematically investigated its potential as an efficient stabilizer for Pickering emulsions. CA treatment maintained the crystalline structure of IDF while increasing crystallinity and surface area, enhancing thermal stability, and decreasing particle size, without significantly altering functional groups. The modified IDF produced emulsions with shear-thinning behavior, with viscosity increasing with higher CA concentrations. CA-modified IDF exhibited improved emulsifying capacity and emulsion stability compared to unmodified IDF, although high CA concentrations diminished these enhancements. The resulting emulsions demonstrated superior viscoelastic properties and stability under centrifugal testing. These findings suggest that CA-modified IDF is a highly effective emulsifier for O/W emulsions, exhibiting excellent stability at 10%, 20%, and 30% CA concentrations, providing a sustainable approach to valorizing sweet potato residue for emulsifier applications.