Effects of Modification on the Structure and Functional Properties of Dietary Fiber in Burdock Root

To improve the hydration and functional properties of dietary fiber from burdock root by ultrasonic treatment combined with hydrogen peroxide modification. The dietary fiber from burdock root was modified by ultrasonic, alkaline hydrogen peroxide, ultrasound-alkaline hydrogen peroxide and alkaline hydrogen peroxide-ultrasonic methods, which was aim to explore the effects of different methods of modification on the structure and functional properties. The results showed that the expansibility and water-holding capacity of dietary fiber from burdock root were significantly (P<0.05) improved by ultrasonic condition associated with 200 W, 10 min and 5% v/v of hydrogen peroxide with pH value of 11. Among them, the alkaline hydrogen peroxide-ultrasonic treatment had the best effect. The particle size data and scanning electron microscope showed that the particle size of dietary fiber was the smallest, and the surface structure was loose and porous after alkaline hydrogen peroxide-ultrasonic treatment. X-ray diffraction and fourier transform infrared spectroscopy showed that dietary fiber modified with alkaline hydrogen peroxidation-ultrasonic treatment had the lowest relative crystallinity, and components of cellulose were redistributed and converted to soluble dietary fiber. Thermogravimetric analysis showed that the thermal stability of dietary fiber treated with alkaline hydrogen peroxide and ultrasound was improved. In vitro antioxidant, α-amylase and α-glucosidase inhibition experiments showed that dietary fiber had strong antioxidant and glucose-digesting enzyme inhibition ability before and after modification, and dietary fiber with the alkaline hydrogen peroxidation-ultrasonic treatment had the strongest cationic free radical scavenging ability on DPPH and ABTS⁺. The half maximal inhibitory concentration of which were 1.07 and 0.89 mg/mL, respectively. The inhibition of α-amylase and α-glucosidase was the best by it, and the half maximal inhibitory concentration was 2.00 and 1.32 mg/mL, respectively. In summary, alkaline hydrogen peroxide-ultrasonic treatment was an excellent method to improve the hydration and functional properties of burdock root dietary fiber, which would provide a theoretical basis for the precise utilization of physicochemical properties of dietary fiber from burdock root and the research of functional foods.