Effects of Psyllium Husk Gel on Phase Redistribution, Microstructure, and Thermal Properties of Whole Wheat Dough and Steamed Bread Quality

Abstract

Psyllium husk gel (PHG) is a soluble dietary fiber with well-documented health benefits, yet its application in whole wheat products is constrained by complex interactions with the gluten network. This study investigated the effects of PHG at 0%, 2%, 8%, and 14% on the phase mass and protein redistribution, microstructure, thermal properties, and steamed bread quality of whole wheat dough. PHG reduced the aqueous phase mass after ultracentrifugation and reallocated proteins predominantly to the water-insoluble fraction, while non-protein substances shifted to the water-soluble fraction associated with insoluble matter. Scanning electron microscopy revealed that PHG transformed the dough from discrete starch granules into continuous aggregates with enhanced granule coverage, and X-ray micro-computed tomography further quantified that PHG increased mean gas cell wall thickness by 3.2%–43.1%, with uniform thickening achieved only at 8% addition. At 14%, PHG disrupted thickness uniformity and reduced the optimal thermal stability observed at 8%, as evidenced by a 28.6% higher tan δ at 60°C and a 15.8% lower residual weight at 350°C. Nevertheless, both 8% and 14% PHG still maintained favorable crumb cellular structure, characterized by higher junction numbers and increased cell wall thickness relative to the control, which resulted in higher springiness even after 7 days of short-term storage. These findings clarify how PHG redistributes dough components and reinforces gas cell walls, and provide a practical basis for improving the quality and storage stability of high-fiber whole wheat steamed bread.