Modulation of Formation, Physicochemical Properties, and Digestion of Ovotransferrin Nanofibrils with Covalent or Non-Covalent Bound Gallic Acid

The impact of covalent or non-covalent bound gallic acid (GA) on the formation, physicochemical properties, and digestion of ovotransferrin (OTF) nanofibrils was comprehensively studied. Thioflavin T fluorescence results revealed that bound GA could inhibit OTF nanofibrillation and that the fibril-inhibitory activity of bound GA was dose dependent. Covalent bound GA exerted stronger inhibition on OTF nanofibrillation than an equal amount of non-covalent bound GA. Atomic force microscopy revealed that covalent bound GA shortened OTF nanofibrils significantly, while non-covalent bound GA did not change the contour length of OTF fibrils remarkably. Bound GA altered diameter of OTF nanofibrils. Both covalent and noncovalent bound GA could alter the zeta potential, surface hydrophobicity, and rheological properties of OTF nanofibrils. Bound GA endowed OTF nanofibrils with a strong antioxidant activity. In vitro gastrointestinal digestion results showed that covalent bound GA elevated the fibril digestion rate better than non-covalent bound GA. Polyphenol binding provided a new approach to modulating the physicochemical properties of protein nanofibrils.