Modulation mechanism of starch gelatinization and gluten network restructuring in wheat flour during atmospheric steam treatment

Abstract

This study elucidates the competitive molecular interplay between starch gelatinization and protein aggregation in wheat flours of varying gluten strengths (strong, medium, weak) during atmospheric steam treatment (AST). Through integrated microstructural, crystallographic, spectroscopic, thermal, chromatographic, and electrophoretic analysis, we demonstrate a phase-dependent shift in dominance between starch gelatinization and protein aggregation. During initial AST (0–2 min), rapid starch hydration drives partial gelatinization, disrupting crystalline domains, reducing short-range molecular order, and promoting amylose-lipid complex formation. With extended treatment (4–10 min), dominance shifted to protein aggregation, where heat-induced conformational unfolding triggered α-helix to β-sheet transitions, exposing buried sulfhydryl groups and hydrophobic residues. These changes facilitated irreversible protein network formation via disulfide cross-linking and hydrophobic associations. Concurrently, protein aggregates adhered to starch granule surfaces, forming physical barriers that restricted water penetration and suppressed further gelatinization. Gluten strength critically modulated these competitive interactions. During initial AST (2 min), gelatinization degrees reached 30.03 %, 35.02 %, and 37.86 % for strong gluten flour (SGF), medium gluten flour (MGF), and weak gluten flour (WGF), reaching 50.83 %, 55.16 %, and 58.14 % after 10 min treatment. Following AST, SGF formed dense, cross-linked protein matrices that tightly encapsulated partially gelatinized starch fragments. In contrast, WGF formed extensive starch gel phases with relatively sparse protein aggregates, resulting in a more open network. MGF displayed a balanced structure with interpenetrating starch and protein networks reflecting intermediate structural characteristics. These findings elucidate the molecular mechanisms governing starch-protein interplay during AST, providing mechanistic foundation for process optimization and targeted wheat-based products development with desirable functional properties.