Influence of in-situ synthesized exopolysaccharides on the quality of gluten-free sorghum sourdough bread

The majority of gluten-free breads on the market are of poor sensory and textural quality. Exopolysaccharides (EPS) formed from sucrose during sourdough fermentation can improve the technological properties of gluten-free breads and potentially replace hydrocolloids. In this study, the influence of in situ formed EPS on dough rheology and quality of gluten-free sorghum bread was investigated. Dextran forming Weissella cibaria MG1 was compared to reuteran producing Lactobacillus reuteri VIP and fructan forming L. reuteri Y2. EPS containing bread batters were prepared by adding 10% and 20% of sourdough. As control served batters and bread containing sourdoughs fermented without sucrose and batters and bread without sourdough addition. The amount of EPS formed in situ ranged from 0.6 to 8.0 g/kg sourdough. EPS formed during sourdough fermentation were responsible for the significant decrease in dough strength and elasticity, with in situ formed dextran exhibiting the strongest impact. Increased release of glucose and fructose from sucrose during fermentation enhanced CO2 production of yeast. Organic acids in control sourdough breads induced hardening of the bread crumb. EPS formed during sourdough fermentation masked the effect of the organic acids and led to a softer crumb in the fresh and stored sorghum bread. Among EPS, dextran showed the best shelf life improvements. In addition to EPS, all three strains produced oligosaccharides during sorghum sourdough fermentation contributing to the nutritional benefits of gluten-free sorghum bread. Results of this study demonstrated that EPS formed during sourdough fermentation can be successfully applied in gluten-free sorghum flours to improve their bread-making potentials.