Abstract: High-yield phytase-producing Pediococcus acidilactici (L-19) and β-glucosidase-producing Pediococcus pentosaceus (J-28) were singly used as a starter culture for black bean-wheat bran sourdough. During sourdough fermentation, lactic acid bacteria growth, acidification properties, enzyme production, and changes in the contents of phytic acid and dietary fiber were investigated. Hydration properties of sourdough gluten proteins were characterized by low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI), and physical and microstructural properties of different black bean-wheat bran sourdough-based doughs were compared. Furthermore, nutritional and baking properties of black bean-wheat bran sourdough bread were evaluated. The results showed that both strains grew well and had strong acidification capacity, but produced different enzymes during sourdough fermentation. After fermentation, the degradation rates of phytic acid in sourdoughs containing L-19 and J-28 were 81.08% and 59.79%, respectively, and the proportions of soluble dietary fiber to the total amount of dietary fiber increased from 22.49% to 31.47% and 44.15%, respectively in the sourdoughs. Black bean and wheat bran interfered with gluten hydration, being detrimental to the formation of a continuous network structure. The destructive effect on the gluten network was attenuated by lactic acid bacteria fermentation. Dietary fiber contents of the L-19 and J-28 based sourdough breads were both higher than 6%, and protein contents were 13.82% and 13.91%, respectively. The sourdough breads had better amino acid profiles and higher in vitro protein digestibility in comparison with wheat bread. In conclusion, both strains effectively improved the nutritional and baking properties of black bean-wheat bran sourdough bread. This suggested their potential applications in the baking industry.

Key words: functional lactic acid bacteria; black bean-wheat bran sourdough; gluten network; rheological properties; nutritional evaluation