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

Abstract

Two types of oat β-glucan oligosaccharides (βG-H and βG-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 βG-H and βG-O possessed the characteristic absorption peak of oat β-glucan. Besides, a new absorption band at 1723 cm−1 in βG-O implied the formation of carboxylic groups caused by oxidative degradation of oat β-glucan. The carbonyl and carboxyl contents increased sharply in βG-O. Viscosity decreased and viscoelastic property varied after degradation of oat β-glucan. During degradation, the properties related to the viscosity of oat β-glucan changed and the swelling power of βG-H and βG-O disappeared. Fat binding capacity and bile acid binding capacity of oat β-glucan increased after acid or oxidative degradation; βG-H exhibited stronger fat binding capacity and βG-O possessed better bile acid binding capacity. In a chemical digestion experiment, the glucose availability of digestive system treated with oat β-glucan, βG-O, and βG-H was 29.92, 36.56, and 20.67 mmol/L, respectively. The results indicated that acid degradation could endow oat β-glucan with enhanced hypoglycemic effect. The antioxidant and antibacterial activities of oat β-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 βG-H is better than that of βG-O, but the βG-O exhibited stronger reducing power. Antibacterial activity of βG-H and βG-O against Staphylococcus aureus is stronger than that against Escherichia coli, and βG-H possessed stronger antibacterial activities than βG-O. The results revealed that degradation methods have a great impact on the structure of oat β-glucan, and further influenced the functionalities and bioactivities of oat β-glucan.