Response of the distribution and molecular transition of gluten proteins and quality of Chinese steamed bread to different hydration levels

This study systematically explored how different hydration levels (45 %, 50 %, and 55 % water addition) affect the evolution of gluten network morphology, distribution, conformational and molecular transition, and moisture migration during the processing of Chinse steamed bread (CSB), and their impact on quality formation. Higher hydration levels resulted in a more uniform distribution and fibrous structure of the gluten network during mixing. However, excessive hydration (55 %) caused gluten fibers to rupture during fermentation. This increased the specific volume but decreased the chewiness and stickiness of CSB. MRI results highlighted that differences in moisture migration and internal structure among samples with different hydration levels were enlarged after steaming. AFM images revealed the increase in both protein molecular chain height and width with increasing hydration level, particularly after steaming. Moreover, high hydration levels promoted the depolymerization of glutenin macropolymers during mixing, fermentation, as well as repolymerization during cooking. These results indicated that both macroscopic qualities and molecular structure of gluten protein became more sensitive to the physical and biochemical processes during CSB processing. These dynamic transitions play a crucial role in determining dough rheological properties and CSB's overall quality. This research offers theoretical insights for precise dough product regulation and understanding underlying mechanisms.