Drying-induced structural transitions in amyloid-like potato protein fibrils

Amyloid-like fibrils derived from plant proteins are increasingly investigated as sustainable, label-friendly building blocks for food-grade functional materials. In this study, we clarified the structural transition of potato protein fibrils formed under combined acidic and thermal conditions and examined how dehydration routes govern their post-processing integrity. Fibrillation was verified across the tested concentration range by ThT fluorescence and Congo Red binding, together with the development of β-sheet-rich assemblies and shifts in surface charge. Among the tested systems, 2.5% (w/v) potato protein was selected as the working concentration, and 12 h was chosen as the representative fibrillation time based on the plateauing behavior of the fibrillation markers. FTIR, CD, and XRD consistently verified cross-β features and showed that these molecular signatures were retained after drying, albeit to varying degrees depending on the process. The amino acid profile of potato protein revealed the presence of aromatic, small, and charged residues, suggesting that fibril formation may be facilitated by a combination of π–π interactions, β-sheet packing, and electrostatic interactions during peptide self-assembly. Among the evaluated methods, freeze-drying preserved β-sheet organization most consistently, whereas spray-drying and oven-drying induced more pronounced structural perturbations, reflected by reduced β-sheet definition and broader physicochemical changes. SEM revealed a porous, interconnected network in freeze-dried samples, but compact, fragmented aggregates in spray- and oven-dried samples. The liquid fibril dispersion showed an apparent particle size of ∼85 nm, compared with ∼55–57 nm after freeze- and spray-drying and 73 nm after oven-drying. Spray-dried powders also exhibited the highest free thiol content (0.0092 μmol/mg) and the lowest disulfide bond level (0.00089 μmol/mg), confirming that drying is a critical post-processing lever governing fibril integrity at the molecular and mesoscale levels. Overall, the findings provide guidance for selecting dehydration strategies when maintaining fibril-associated signatures is important for subsequent formulation in food structuring and bio-based material applications.