Exopolysaccharides in sourdough fermented by Weissella confusa QS813 protected protein matrix and quality of frozen gluten-red bean dough during freeze-thaw cycles

Quality loss of frozen dough products were mainly attributed to ice recrystallisation on gluten and yeast activity during frozen storage. Little was reported on role of sourdough metabolites and acidification on gluten protein behavior during frozen storage of dough. Here, the effects of in situ formed exopolysaccharide (EPS) in red bean sourdough fermented by Weissella confusa QS813 and sourdough acidification on gluten protein matrix and quality of frozen gluten-red bean dough was investigated during 0, 1, and 5 freeze-thaw cycles (FTC). Underlying mechanisms were explored to compare changes in gluten, water distribution, rheological and microstructural properties of frozen gluten-red bean dough during FTC. Gluten protein conformation analysis showed that EPS in sourdough and sourdough acidification reduced rate of increase of glutenin macropolymer (GMP) depolymerization (3.07%), GMP content (0.88%), and free sulfhydryl content in frozen gluten-red bean doughs during FTC. Secondary structure analysis showed that β-turns increased while α-helix and β-sheet structures decreased in frozen gluten-red bean doughs with sourdough during FTC. EPS in red bean sourdough reduced water distribution by enhancing water binding capacity. This suggested that EPS probably formed bonds with gluten and red bean components like proteins, resulting in a dough structurally tolerant to distortions caused by ice recrystallisation during FTC. Furthermore, synergistic interactions between EPS and acidification improved viscoelastic properties and stabilized microstructural integrity of frozen gluten-red bean doughs. These findings gave new insights and suggested potential clean label application of sourdough fermentation to enhance legume ingredient functionality in frozen dough products in bakery food industry.