Abstract: In this experiment,black bean hulls were used as experimental materials and modified by enzymatic method to improve the extraction rate of soluble dietary fiber (SDF) and the extraction process conditions of soluble dietary fiber from black bean hulls was optimized by response surface methodology.The results showed that the optimum conditions were as follows:the enzyme addition (cellulase∶hemicellulase = 1∶2) was 5%,the pH was 4.6,the temperature was 50  ℃ and the time was 2 h.Under this condition,the yield of SDF was 14.90% and this result is close to the theoretical value.The results showed that the water holding capacity and swelling force of enzymatic modified SDF were 3.71% and 10.97%,respectively.Scanning electron microscopy shows that the particle surface of enzymatic modified SDF was rougher,the alveolate pore was fewer,the structure was more concentrated and the particle size and shape were more uniform than original SDF.This study provides some theoretical guidance for the development of high-dietary fiber food and the comprehensive utilization of black bean hull.

Key words: black bean hull, soluble dietary fiber, response surface methodology, physical and chemical properties, super-microstructure