Study on the functional properties and structural characteristics of soybean soluble polysaccharides by mixed bacteria fermentation and microwave treatment

The soybean soluble polysaccharide was prepared by mixed fermentation of lactic acid bacteria and Neurospora crassa and microwave treatment. The functional properties and structure characteristics of soybean soluble polysaccharide before and after modification were compared. Results revealed that after fermentation treatment, the content of soybean soluble polysaccharide increased to 7.09%, which was 3.16 times that of raw materials, and the microwave treatment was further increased to 7.69%. The glucose adsorption capacity, glucose dialysis retardation index and the α-amylase activity inhibition ration of soybean soluble polysaccharides increased significantly, promotes intestinal flora growth in vitro after fermentation of mixed bacteria and microwave treatment. At the same time, the analysis of monosaccharide composition and structural characteristics showed that the monosaccharide components of soybean soluble polysaccharide were redistributed after modification treatment, Scanning electron microscopy showed that modified soybean soluble polysaccharide has a larger surface area; Fourier Transform Infrared spectroscopy and X-ray Diffraction proved that the modification has slight changes in the functional groups and crystal structure of soybean soluble polysaccharide. These results suggested that okara may be a potentially inexpensive source of natural soybean soluble polysaccharide and a potential functional food ingredient. •The functional properties and structural characteristics of U-SSPS, F-SSPS and M-SSPS were compared.•SSPS has better glucose adsorption capacity after modification treatment.•Mixed fermentation and microwave treatment redistribute the monosaccharide content of SSPS.