Complexation with Ionic Polysaccharides Mitigates pH-Dependent Degradation of Soy Protein Fibril Structure and Functionality
Sanjana Sawant, Audrey L. Girard
Abstract
This study explored complexation of soy protein fibrils with gellan gum (anionic) and chitosan (cationic) to mitigate pH-induced degradation of fibril structure and function. Unfibrillated proteins combined with polysaccharides were studied as controls. Chitosan complexation preserved fibril integrity, with a moderate particle size increase (∼2.5x) and AFM imaging of fibrils alongside some aggregates when pH was increased from 2 to 4. FTIR analysis confirmed that chitosan best preserved the fibril β-sheet structure, primarily through electrostatic interactions. A Rapid Visco Analyzer study revealed that chitosan-modified fibrils retained their gelling ability at pH 4 (final viscosity ≈ 115 cP), comparable to fibrils at pH 2 (∼93 cP). Gellan gum complexation resulted in the formation of self-supporting gels at pH 7 (final viscosity ≈ 688 cP), likely due to electrostatic repulsion between like-charged components. Overall, this work provides valuable insights into mitigating pH-induced fibril degradation, thus expanding the potential applications of protein fibrils in food matrices.