Concentration-dependent fibrillation of whey protein isolate:Structural and antioxidant properties

Whey protein isolate amyloid fibrils (WPIF) have attracted extensive research interest due to their stable structural characteristics and desirable functional attributes. However, limited research has been conducted on the relationship between the structure and antioxidant activity of WPIF. WPIF with various flexible and linear structures were successfully prepared by adjusting the fibrillation concentrations. The structure and antioxidant properties of WPIF were characterized, revealing multiscale structural transformations of WPIF in response to different fibrillation concentrations. WPIF with low fibrillation concentrations (1-3 %) displayed short flexible structures. WPIF with high fibrillation concentrations (3-5 %) displayed long rigid structures. Long rigid amyloid fibrils possessed enhanced antioxidant properties compared to short flexible amyloid fibrils. The active amino acids were more easily exposed to the surface of long rigid amyloid fibrils, enhancing free radical scavenging activity and ferric reducing power. The partial gelation of WPIF occurred at high fibrillation concentrations (4-5 %), which prevented the exposure of oxidizable amino acids and thus reduced the antioxidant activity of WPIF. This study revealed the relationship between fibrillation concentrations and the structural and antioxidant activity of WPIF, thereby furnishing a theoretical basic for the optimized utilization of WPIF in formulated foods.