Studies On The Ultrasound-assisted Extraction And Characteristic Of Soybean Dietary Fiber

Dietary fibre (DF), is the general name for carbohydrates and lignin that cannot be digested by human body, and can be divided into soluble dietary fibre (SDF) and insoluble dietary fibre (IDF). DF is regarded as "the seventh nutrient" followed by water, protein, fat, carbohydrate, minerals and vitamins, which played an important role in treating obesity, resisting gastrointestinal cancer, depleting exogenous harmful substances, resisting oxidation and eliminating free radicals. Soybean dregs, as a high quality DF resource, have DF at 50%-70% of total masses. In this paper, we used the quaternion quadratic general rotation design to optimize the technology for soybean dietary fiber extraction by ultrasonic extraction method based on the single factor experiments. The structure and physical properties of products were characterized by infrared spectra analysis, UV spectroscopy and TG-DTA. We also investigated on the processing properties of the soybean dietary fiber, as well as their in vitro anti-oxidant effects and in vivo hypolipidemic effects.The single factor experiments and the quaternion quadratic general rotation unitized design experiments showed that the optimal conditions for SDF extraction were the ratio of material to water at 1:55 (g:mL), cellulase addition at 1.5%, ultrasound power at 700 W and ultrasonic temperature at 50℃, while the optimal conditions for IDF extraction were the ratio of material to water at 1:55 (g:mL), cellulase addition at 2.0%, ultrasound power at 600 W and ultrasonic temperature at 50℃. Under above conditions, the extraction rate of the SDF was 9.39% and the extraction rate of the IDF was 82.11%.Result of structure characterization of DF indicated that it has the typical DF properties. Compared to the DF extracted by traditional alkaline method and enzymolysis method, SDF extracted by ultrasound-assisted extraction has more C-H,C=O,COOR and free hydroxyl groups, strong thermal oxidation behaviors, suggesting that it has better processing properties, better resistance to oxidation and better effect of lowering blood lipid.The processing property test showed that IDF has good swelling capacity, water holding capacity, water binding capacity, cation exchange capacity and fat absorption capacity at different temperatures.The result of antioxidant experiment in vitro showed that SDF extracted by ultrasonic extraction can scavenge 02·- DPPH·,·OH and H2O2. The pharmacological test of SDF indicated that among the three methods, ultrasonic method at 400mg/kg.bw gave the best result for the reducing effect of SDF. TC, TG and LDL-C were down to 20.4%,21.0%,35.3% respectively and HDL-C was increased 17.3% than that of the model group. The SDF extracted by alkaline and enzyme method has no significant reducing effect.The results would provide reference for comprehensive utilization of soybean dregs in order to improve the addition value of soybean processing byproducts, extend industry chain of soybean products and reduce the pollution of soybean dregs to environment.