Purification, characterization, and antioxidant activity of polysaccharides from Okara

A neutral polysaccharide (SSPS-N) and an acidic polysaccharide (SSPS-A) were isolated from Okara by anion-exchange chromatography. The physical and chemical properties of polysaccharides were studied by HPLC, FT-IR, and SEM. The results showed that SSPS-N might be a galactomannans with a lamella-like structure, and SSPS-A might be an arabinogalactan with a complete porous structure. Furthermore, a new neutral soybean soluble polysaccharide (SSPS-N-b) with a molecular weight of 8.6 kDa was isolated from SSPS-N, and its fine structure was analyzed by GC–MS, enzymatic analysis, and NMR. The results showed that SSPS-N-b was a mixture of β-1,4-galactan and glucomannan, which (1→4)-β-d-linked mannose and (1→4)-β-d-linked glucose were connected alternately, and it was in parallel with β-1,4-galactan. The antioxidant activity results showed that β-1,4-Galactan in SSPS-N-b was identified as the main activity domain. This result will be utilized for the development of SSPS as novel functional foods and medicine. Practical applications Soluble soybean polysaccharide is considered to be a functional component in food because of their biological activities. The physical and chemical properties and antioxidant activity of polysaccharides from Okara show potential applications in novel functional foods and medicine.