Improvement on the quality of frozen dough steamed bread by fermented glutinous rice wine filtrate: Insights into the thermally induced physicochemical characteristics of gluten and starch

This study investigated the effects of fermented glutinous rice wine filtrate (FGF) and its fractions (supernatant, FGF-S; lees, FGF-L) on the quality of frozen dough steamed bread (FDSB), and explored the underlying mechanisms in enhancing dough's gas retention capacity during steaming process. FGF and FGF-S significantly increased the specific volume, lightness, and gas cell ratio, and significantly reduced hardness of FDSB. FGF-L, rich in microorganisms but lacking key metabolites, failed to significantly improve the quality of FDSB compared with the control group. FGF and FGF-S significantly increased elevated dough volume and gas hold ratio of dough after 14 days of frozen storage. Dynamic thermo-mechanical analysis showed that FGF-S significantly increased T_onset and T_peak of dough, indicating effective delay in starch gelatinization and gas cell rupture. According to the results of protein extractability in SDS and subunits distribution, FGF-S inhibited the release of gliadin from gluten protein and depolymerization of high molecular weight glutenin subunits to low molecular weight glutenin subunits during frozen storage. Meanwhile, FGF-S enhanced gluten polymerization and gas retention during the initial stage (<65 °C) of steaming while preventing formation of overly dense gluten network at the later stage (≥90 °C). Results of reverse-phase-HPLC at different temperatures confirmed that FGF-S inhibited thermally induced cross-linking between gliadin and glutenin subunits at temperatures exceeding 90 °C. Moreover, FGF-S delayed thermal transition and pasting of starch, reduced pasting viscosities, and facilitated diffusion and expansion of gas cells. As a clean label ingredient, FGF holds strong potential for use in frozen dough.