Oat protein-EGCG-sugar beet pectin ternary complexes: Role of pectin in driving non-covalent interactions and improving functional properties

To overcome the functional limitations of plant proteins, oat protein (OP) was first complexed with epigallocatechin gallate (EGCG) and then further assembled with sugar beet pectin (SBP) to obtain a ternary complex. The interaction mechanisms and functional properties of the resulting ternary complex were systematically characterized across varying mass ratios. Turbidity analysis confirmed ternary complex formation. Particle size characterization revealed minimal variation at low SBP ratios (OP-EGCG: SBP = 4:1 to 2:1), while a significant increase from 170 to 210 nm occurred at the 1:1 ratio, with scanning electron microscopy further confirming SBP-induced particle aggregation at this high ratio. FTIR spectroscopy revealed hydrogen bonding and suggested hydrophobic interactions. ITC further confirmed the dominant role of hydrogen bonds in the complexes. The hydrogen-bonded non-covalent interaction patterns between the ternary complexes were further visualized through molecular docking. SBP reduced interfacial tension to a minimum value of 6.49 mN/m at a 2:1 ratio, leading to improved emulsification activity and stability. Conversely, excess SBP (1:1 ratio) increased interfacial tension and compromised emulsification performance. Short-term storage (7 days) confirmed SBP's sustained protection of antioxidant capacity. Collectively, this study elucidated interaction mechanisms between SBP and protein-flavonoid complexes, providing mechanistic insights for functional food applications.