Effect of microwave-assisted acid extraction on the physicochemical properties and structure of soy hull polysaccharides

This study aimed to investigate the effect of the extraction method on the physicochemical and structural properties of soy hull polysaccharide (SHP). Four types of SHP were extracted from soy hulls under the conditions of microwave-assisted oxalic acid (or citric acid) extraction and hot water extraction: MOSP, MCSP, HOSP and HCSP. The results showed the polysaccharide extraction rate of MOSP, HOSP, MCSP and HCSP was 11.97%, 8.99%, 6.22% and 4.74% respectively. SHP is mainly composed of arabinose, galactose, mannose and galacturonic acid, and the relative molecular weight range was 10(4)-10(6) Da. FT-IR showed that SHP contained hydroxyl, amido, ester, carboxyl and ether bonds. The fingerprints of SHP showed that the main chain composition and molecular weight of the four SHPs were similar, and the main constituent unit was 1,4-alpha-D-GalpA. In addition, the branched chains of polysaccharides contained 1,5-alpha-L-arabinoside bond, beta- 1,4-mannoside bond and beta-1,4-galactoside bond.