Protein composition and rheological properties of liquid sourdough fermented by different lactic acid bacteria and...

The interaction between lactic acid bacteria (LAB) and yeasts of sourdough could affect its application quality. This study used single and mixed strains of lactic acid bacteria and yeast to ferment type II liquid sourdough, systematically investigating changes in sourdough protein components, protein secondary structure, and rheological properties during fermentation, as well as the degradation of alcohol soluble proteins. The results show that metabolic differences among different strains lead to significant changes in the protein composition and rheological properties of liquid sourdough. During fermentation, the contents of globulin, gliadin and glutenin in sourdough gradually decreased. The sourdough fermented by mixed strains of Saccharomyces cerevisiae J2808 and L. plantarum LG1034 had the lowest globulin content (2.12 mg/g), while that fermented by L. plantarum LG1034 alone had the lowest gliadin contents (0.27 mg/g) and glutenin contents (11.98 mg/g). Free sulfhydryl content increased continuously in single yeast fermented sourdough during fermentation, whereas it initially decreased then rose in sourdough fermented by single LAB or mixed strains of lactic acid bacteria. Furthermore, except for Y2 sourdough fermented with S. cerevisiae J2808, the ordered structure of gliadin increased significantly (p < 0.05) in other sourdough samples. Compared with single LAB fermented samples, mixed fermented sourdough exhibited a reduced blue shift of gliadin peak wavelength (λ _max) and enhanced fluorescence intensity, indicating that LAB yeast interactions could reduce gliadin aggregation and degradation. Overall, protein composition is related to the rheological properties of liquid sourdough, particularly viscoelasticity during yeast fermentation.