Enhancing emulsifying properties of lentil protein fibrils through EGCG mediation and the mechanism study

Amyloid-like fibrils derived from plant proteins has provided a strategy to improve plant protein physicochemical performance and has substantial untapped potential for application in stabilizing oil-in-water (O/W) emulsions. This study aimed to explore the structural modifications of lentil protein fibrils (LPF) and their emulsifying properties facilitated by EGCG, with the proposal of potential underlying mechanism. The structure and morphology of LPF-EGCG complexes were characterized by particle size, Fourier transform infrared (FTIR) spectroscopy, fluorescence spectroscopy, surface hydrophobicity, contact angle, and transmission electron microscope (TEM). Results showed that the binding of LPF to EGCG was driven by hydrogen bonding and hydrophobic interaction. Both interactions play a pivotal role in the cross-linking of LPF and the transformation of the elongated fibrillar morphology of LPF into fibrillar aggregates networks, and even large-sized non-amyloid fibril aggregates, with particle size increasing from 564 nm to 3221 nm. Droplet size and confocal laser scanning microscopy (CLSM) results showed that the O/W emulsions containing 30% and 50% (w/w) oil stabilized by LPF-EGCG complex (EGCG-to-protein ratio, EGCG/P = 0.04) exhibited smallest and uniform droplet sizes (9.25 μm and 11.50 μm, respectively). The reason was that an appropriate concentration of EGCG can fine-tune the hydrophobic/hydrophilic balance and network structures of LPF, thus enhancing the stability of emulsions. Moreover, emulsions containing 30% (w/w) oil stabilized by LPF-EGCG complexes (EGCG/P > 0.02) exhibited rheological behavior similar to emulsions containing 50% oil stabilized by LPF alone, indicating potential applications in the production of fat reduced emulsion with desirable textures. These findings provide a new perspective on the structural remodeling of plant-based protein fibrils mediated by phenolic compounds, expanding their application in the production of fat-reduced emulsion-based food products.