Ultrasonic-microwave Assisted Enzymatic Extraction of Water-soluble Dietary Fiber from Black Soybean Hull and Its Physicochemical Properties

The water-soluble dietary fiber from black soybean hull was extracted by ultrasound-microwave-assisted enzymatic method,and its physicochemical properties were analyzed. The results showed that the yield of water-soluble dietary fiber from black soybean peel could reach 19.12%±0.23% when the ratio of material to liquid was 1:25 (g/mL),the amount of papain was 20 mg/g and the temperature was 60℃ for 23 min. The physicochemical properties of water-soluble dietary fiber from black soybean peel showed that the swelling power of the dietary fiber was 585.71%,water-holding capacity was 11.89 g/g,oil-holding capacity was 10.52 g/g,emulsifying stability(EC)was 42.45%,emulsifying stability(ES)was 64.76%,glucose adsorption value was 19.72 mmol/L,glucose delay index were 34.65,30.48,25.72 mmol/g at 30,60 and 120 min,respectively. The viscosity of 10% black soybean peel water-soluble dietary fiber solution was 0.0093 Pa·s.Microstructure study showed that black soybean peel water-soluble dietary fiber had a large number of pores and wrinkles on its surface,which was conducive to improving its adsorption capacity. Infrared spectrum analysis showed that water-soluble dietary fiber from black soybean peel had typical polysaccharide characteristics.