Effect of Thermal Treatment on the Self-Assembly of Wheat Gluten Polypeptide

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.

Formation, structural characteristics and specific peptide identification of gluten amyloid fibrils

This research investigates the formation of amyloid fibrils using enzymatically hydrolyzed peptides from gluten, including its components glutenin and gliadin. After completing the fibrillation incubation, the gluten group demonstrated the most significant average particle size (908.67 nm) and conversion ratio (57.64 %), with a 19.21 % increase in thioflavin T fluorescence intensity due to self-assembly. The results indicated increased levels of β-sheet structures after fibrillation. The gliadin group exhibited the highest zeta potential (∼13 mV) and surface hydrophobicity (H0 = 809.70). Around 71.15 % of predicted amyloidogenic regions within gliadin peptides showed heightened hydrophobicity. These findings emphasize the collaborative influence of both glutenin and gliadin in the formation of gluten fibrils, influenced by hydrogen bonding, hydrophobic, and electrostatic interactions. They also highlight the crucial role played by gliadin with amyloidogenic fragments such as ILQQIL and SLVLQTL, aiming to provide a theoretical basis for understanding the utilization of gluten proteins.

Amyloid-like Aggregation of Wheat Gluten and Its Components during Cooking: Mechanisms and Structural Characterization

Amyloid-like aggregation widely occurs during the processing and production of natural proteins, with evidence indicating its presence following the thermal processing of wheat gluten. However, significant gaps remain in understanding the underlying fibrillation mechanisms and structural polymorphisms. In this study, the amyloid-like aggregation behavior of wheat gluten and its components (glutenin and gliadin) during cooking was systematically analyzed through physicochemical assessment and structural characterization. The presence of amyloid-like fibrils (AFs) was confirmed using X-ray diffraction and Congo red staining, while Thioflavin T fluorescence revealed different patterns and rates of AFs growth among wheat gluten, glutenin, and gliadin. AFs in gliadin exhibited linear growth curves, while those in gluten and glutenin showed S-shaped curves, with the shortest lag phase and fastest growth rate (t1/2 = 2.11 min) observed in glutenin. Molecular weight analyses revealed AFs primarily in the 10-15 kDa range, shifting to higher weights over time. Glutenin-derived AFs had the smallest ζ-potential value (-19.5 mV) and the most significant size increase post cooking (approximately 400 nm). AFs in gluten involve interchain reorganization, hydrophobic interactions, and conformational transitions, leading to additional cross β-sheets. Atomic force microscopy depicted varying fibril structures during cooking, notably longer, taller, and stiffer AFs from glutenin.