Effects and underlying mechanisms of insoluble dietary fiber and ferulic acid on the crumb structure of steamed bread

This study investigated the effects and underlying mechanisms of insoluble dietary fiber (IDF) and ferulic acid (FA) on the crumb structure of steamed bread. Both IDF and FA had significant (p < 0.05) adverse effects on the crumb structure of steamed bread, except for small doses of FA (0.3 g), while the simultaneous addition of IDF and FA exacerbated the adverse effects. IDF reduced the bound water and free water content of the dough and increased the immobilized water content due to physical filling and strong water absorption, which hindered the formation of gluten. Moreover, IDF mainly reduced the extractability of low molecular weight glutenin subunit (LMW-GS), thereby promoting glutenin polymerization, which further limited the extensibility and fermentation of the dough. The fermentation height and CO2 production of the dough with FA added decreased rapidly to 0 mm and 4 mL, and then remained stable. This was attributed to the fact that FA resulted in a denser gluten network structure. The extractability of glutenin indicated that FA reduced the extractabilities of glutenin subunits and increased the extractabilities of gliadin subunits. The extractability of LMW-GS with 1.8 g of FA was reduced by 25.03% compared with the control sample, which far exceeded the 6.39% reduction of high molecular weight glutenin subunit. This revealed that FA was mainly through cross-linking with LMW-GS to promote gluten polymerization. Moreover, the addition of IDF + FA exacerbated the gluten polymerization through the formation of macromolecular polymers, which further affected the crumb structure of steamed bread.