Structural characterization of polysaccharides from lactobacillus helveticus MB2-1 fermented milk and their...

The poor stability of single casein (CAS) gel limits its widespread industrial application, the addition of polysaccharides usually can be helpful to improve its property. In this study, the effect and mechanism of three purified polysaccharides obtained from Lactobacillus helveticus MB2-1 fermented milk (LHP1, LHP2, LHP3) on the gel properties of CAS were investigated. The results showed that LHP1, LHP2, and LHP3 exhibited distinct structural and charge characteristics, corresponding to neutral, weakly negative, and strongly negative, respectively. The addition of LHP1, LHP2 and LHP3 (0.5-2.0 %, w/v) all improved the particle size, water-holding capacity, rheological properties, and microstructure of CAS gels in a concentration-dependent manner. Through multispectral analysis, surface hydrophobicity, free sulfhydryl content, and protein solubility analysis, it was concluded that the molecular weight and charge characteristics of polysaccharides played a critical role in the formation of the CAS/LHP1, CAS/LHP2, CAS/LHP3 gel composites. Molecular simulations revealed high stability in CAS/LHP1, CAS/LHP2, and CAS/LHP3 composites. CAS-LHP1 interacted mainly via hydrogen bonding, CAS-LHP2 through weak electrostatic interactions, and hydrogen bonding at high concentrations, while CAS-LHP3 involved strong electrostatic interactions and hydrogen bonding. These findings provided a theoretical basis for regulating the stability of CAS gel systems by L. helveticus MB2-1 polysaccharides addition.