Abstract
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.
Highlights
Soybean protein is a representative plant protein and plays a decisive role in a variety of food systems: (1) increase protein content and maintain amino acid content; (2) provide beneficial physiological components; and (3) provide good processing properties [1]
Fermentation by lactic acid bacteria (LAB) stands out from the many solidification methods, except the role of LAB fermentation itself, EPS produced by LAB plays an indispensable role [2,3]
EPS-producing LAB fermentation induced gel (ELFG) are prepared by water phase and soybean protein, which are different from organogels and are more effective for the delivery of hydrophilic substances, whether in the food or pharmaceutical industries
Summary
Soybean protein is a representative plant protein and plays a decisive role in a variety of food systems: (1) increase protein content and maintain amino acid content; (2) provide beneficial physiological components; and (3) provide good processing properties [1]. More and more concerns are focused on the gelation of soy protein, which has a positive effect on the texture of food, and improves the sensory and flavor by providing the spatial three-dimensional (3D) network structure for preserving food ingredients [1]. EPS-producing LAB fermentation induced gel (ELFG) can be considered as a novel hydrogel. ELFGs are prepared by water phase and soybean protein, which are different from organogels and are more effective for the delivery of hydrophilic substances, whether in the food or pharmaceutical industries. The mechanism of improving the properties of fermentation induced soybean protein gels (FSGs) is not clear, especially the effects of EPS properties on gelation properties. The most promising LAB strain for the application in soybean protein foods could be identified
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