Effect of microbial exopolysaccharide on wheat bran sourdough: Rheological, thermal and microstructural characteristics.

Rheological, thermal and microstructural properties of wheat bran sourdough (WBS) containing different levels of microbial exopolysaccharide (EPS) extracted from Lactobacillus plantarum were investigated. All sourdough samples showed pseudoplastic behavior and the highest apparent viscosity was achieved at 1.5% EPS. The values of consistency coefficient of 1 and 2.5% EPS were significantly lower than for the dough without EPS. Increasing EPS in WBS produced a decrease in the storage, loss, and complex moduli of the sourdough, except that made with 1.5% EPS. This can be attributed to the microbial EPS structure and its ability to bind with water. It can be concluded, due to high hygroscopicity of EPS, WBS containing EPS had a lower access to water and other dough constituents. Thermal and microstructural results showed that EPS strongly modified starch gelatinization by prohibiting water access to amorphous parts of the granules and stabilized crystalline regions of starch causing an increase of end set temperature.

Response surface methodology for investigating the effects of sourdough fermentation conditions on Iranian cup bread properties.

In this study, the dominant lactic acid bacteria present in whole wheat sourdough was isolated and identified as Lactobacillus plantarum by molecular methods, before being utilized as the starter culture in the processing of sourdough cup breads. Subsequently, the effects of sourdough fermentation time, ash content, and sugar content on bread quality attributes were investigated by response surface methodology. In terms of the independent variables, the best polynomial models were fitted for bread hardness, chewiness, specific volume, total color difference (TCD), porosity and overall acceptability (OAA). Based on statistical analysis (P < 0.05), the effect of fermentation time on hardness and TCD was significant; ash content influenced specific volume and TCD significantly. In comparison with other functions, the interaction between fermentation time and sugar content had a significant (P < 0.05) influence on bread OAA. Furthermore, a strong positive correlation was ascertained between sourdough total titratable acidity and most of the quality attributes of cup bread (especially hardness, specific volume and OAA). Accordingly, the control of sourdough fermentation conditions is influential on microbial activity and metabolites, which affect bread quality characteristics.