Investigation of the Differences in Amyloid-Like Fibrils Derived from Wheat Gluten with Varying Structures under Typical Food Processing Conditions

This study investigates the differences in physicochemical properties, structural characteristics, and fibril morphology among three wheat gluten with distinct secondary structure contents (A protein: high α-helices, low β-sheets, low random coils; C protein: low α-helices, high β-sheets, high random coils; B protein: intermediate structure) when amyloid-like fibrils (AFs) are formed under boiling and steaming conditions. Congo red absorption, polarized light microscopy, and X-ray diffraction confirmed the formation of AFs in proteins A, B, and C under boiling and steaming conditions. Thioflavin T fluorescence revealed that C-protein-derived fibrils (CPF) exhibited the highest intensity, indicating the strongest fibril-forming ability. SE-HPLC analysis showed a gradual increase in molecular weight and AFs contents with prolonged heating. Increased heating time led to larger particle sizes, higher β-sheet content, and involvement of aromatic amino acids in β-sheet formation via π-π stacking, promoting fibril growth. These changes were more pronounced under steaming conditions. AFM revealed that under steaming, the C protein formed longer and taller fibril structures than under boiling. This work establishes a theoretical foundation for understanding the growth mechanism of AFs formed by gluten proteins with different structures during food processing.