Effect of Polydextrose and Its Complex on the Pasting, Function, and Microstructural Characteristics of Low-Gluten Wheat Dough and Steamed Buns

To improve the gluten strength of low-gluten dough and achieve better-quality steamed buns, this study analyzed the pasting, function, and microstructural characteristics of low-gluten wheat dough and steamed buns with added 3–10% polydextrose (PD) and a complex dietary fiber (PIF) (i.e., PD, inulin, and fructooligosaccharides). Compared to the control, adding 3–10% PD or PIF to low-gluten flour increased the texture parameters of steamed buns, including the hardness, adhesiveness, cohesiveness, gumminess, and chewiness, with maximal improvements at 5% PD or PIF addition, while springiness and resilience decreased. Further, the surface color and brightness increased while the color difference decreased. The sensory parameters, including the specific volume, stickiness, toughness, and elasticity, improved, leading to an increased total score. Adding 3–10% PD or PIF reduced the retrogradation viscosity, retrogradation torque, and retrogradation of amylopectin in low-gluten flour. The dough development time increased with increasing dietary fiber (DF), consistent with the better adhesiveness and elasticity in the sensory analysis. As the DF addition amount increased, the breakdown viscosity of flour suspensions and the breakdown torque of the dough decreased. However, the pasting temperature of flour suspensions and the peak temperature of gelatinization both increased. The percentages of α-helices, β-turns, and random coils increased with increasing PD or PIF addition in both dough and steamed buns, indicating increasing stability of gluten proteins. Microstructural observations confirmed that, compared to added PD, the pores and interspaces in the dough became more numerous, larger, and deeper with increasing PIF addition from 3% to 10%. Similar to PD addition, as the PIF addition increased from 3% to 10%, the resistance to gluten network formation increased, the number of air bubble cells in steamed buns gradually decreased, and the chewiness increased; however, compared to PD addition, PIF addition resulted in a larger specific volume of the steamed buns, greater adhesive force, and easy detachment of large crumbs from the cut surface, while the hardness and sensory scores of the steamed buns increased. This study could help develop DF-rich low-gluten steamed buns with better mouthfeel and textural parameters.