Amyloid fibrils from black kidney bean protein self-assemble into hydrogels: Impact of heating time on gel structure and rheological properties.

Fibrillation of plant proteins is a promising approach to enhance their gel properties. In this study, black kidney bean protein isolate self-assembled into amyloid fibrils and subsequently formed hydrogels at a concentration of 2.0 wt% after thermal treatment at pH 2.0. Gel structure and rheological properties were modulated by regulating the acid-heat incubation time (0-72 h). With increased incubation time, the black kidney bean protein fibrils (BKPFs) transitioned through distinct states: sol state (8 h), gel state formed by fibril entanglement (12-20 h), and disrupted gel state by partial depolymerization of fibril aggregates (>24 h). Rheological analysis revealed that the gels at 16 h had maximum storage modulus (159.9 Pa). Small-angle X-ray scattering indicated that BKPFs highly aggregated (R = 49.49 nm) with a more compact mass fractal structure (D = 2.0) at 16 h. Cryo-scanning electron microscopy images showed the formation of a homogeneous and dense three-dimensional gel network structure at 12 h.