Effect of acid and oxidative degradation on the structural, rheological, and physiological properties of oat β-glucan

Two types of oat beta-glucan oligosaccharides (beta G-H and beta G-O) with similar molecular weights were prepared by using acid and oxidative degradation methods, respectively. Their structures were characterized and the physiological functionality were evaluated. Fourier transform infrared spectroscopy (FT-IR) results showed that both beta G-H and beta G-O possessed the characteristic absorption peak of oat beta-glucan. Besides, a new absorption band at 1723 cm 1 in beta G-O implied the formation of carboxylic groups caused by oxidative degradation of oat beta-glucan. The carbonyl and carboxyl contents increased sharply in beta G-O. Viscosity decreased and viscoelastic property varied after degradation of oat beta-glucan. During degradation, the properties related to the viscosity of oat beta-glucan changed and the swelling power of beta G-H and beta G-O disappeared. Fat binding capacity and bile acid binding capacity of oat beta-glucan increased after acid or oxidative degradation; beta G-H exhibited stronger fat binding capacity and beta G-O possessed better bile acid binding capacity. In a chemical digestion experiment, the glucose availability of digestive system treated with oat beta-glucan, beta G-O, and beta G-H was 29.92, 36.56, and 20.67 mmol/L, respectively. The results indicated that acid degradation could endow oat beta-glucan with enhanced hypoglycemic effect. The antioxidant and antibacterial activities of oat beta-glucan increased after acid or oxidative degradation. The DPPH free radical scavenging activity, chelating ability on ferrous iron, and inhibition activity of lipid peroxidation of beta G-H is better than that of beta G-O, but the beta G-O exhibited stronger reducing power. Antibacterial activity of beta G-H and beta G-O against Staphylococcus aureus is stronger than that against Escherichia coli, and beta G-H possessed stronger antibacterial activities than beta G-O. The results revealed that degradation methods have a great impact on the structure of oat beta-glucan, and further influenced the functionalities and bioactivities of oat beta-glucan.