Protein fibril-mediated inhibition of lotus seed starch retrogradation

Controlling heat-induced molecular self-assembly of starch during retrogradation is pivotal to improving the quality of starch-based products. Protein-derived amyloid fibrils, featuring an open, accessible architecture and pronounced amphiphilicity, represent a promising class of functional ingredients capable of modulating molecular interactions and structural assembly in starch systems during retrogradation. However, the influence of protein fibrils on starch retrogradation remains poorly understood. In this work, lotus seed starch was incorporated with whey protein-derived fibrils (WPFs) at 0-25% (w/w) to examine their effects on the structure, rheological behavior, and in vitro digestibility of retrograded starch. The results showed that the addition of WPFs led to a pronounced reduction in starch crystallinity after short-term retrogradation (8 h). At a fibril content of 15%, starch crystallinity was reduced by approximately 47.6%, which was mainly attributed to a decreased proportion of B-type polymorphs associated with double helical structures. Increasing the fibril content to 25% further promoted V-type crystallization of starch-associated complexes, thereby enhancing starch crystallinity and molecular ordering. Relative to fibril-free counterparts, starch systems containing 15% WPFs exhibited weakened gel viscoelasticity and increased digestibility. These findings reveal the inhibitory role of protein fibrils on starch retrogradation, with implications for retrogradation control in starch-based products.