A Relation between Exopolysaccharide from Lactic Acid Bacteria and Properties of Fermentation Induced Soybean Protein Gels

Exopolysaccharide (EPS) producing lactic acid bacteria (LAB) is considered to be an effective texture improver. The effect of LAB strains (different EPS production capacity) on physicochemical properties (texture profile, water distribution, rheological properties, and microstructure), protein conformation, and chemical forces of soybean protein gel was investigated. Correlations between EPS yield and gel properties were established. Large masses of EPS were isolated from L. casei fermentation gel (L. casei-G, 677.01 ± 19.82 mg/kg). Gel with the highest hardness (319.74 ± 9.98 g) and water holding capacity (WHC, 87.74 ± 2.00%) was also formed with L. casei. The conversion of β-sheet to α-helix, the increased hydrophobic interaction and ionic bond helped to form an ordered gel network. The yield was positively correlated with hardness, WHC, A₂₂, viscoelasticity, and viscosity, but negatively correlated with A₂₃ (p < 0.05). The macromolecular properties of EPS (especially the yield) and its incompatibility with proteins could be explained as the main reason for improving gel properties. In conclusion, the EPS producing LAB, especially L. casei used in our study, is the best ordinary coagulate replacement in soybean-based products.