Abstract: The preparation of dietary fiber based on soy hull with enzymic hydrolysis, acid hydrolysis and alkali dissolutionwas studied.The advantages and disadvantages of preparation method were compared, and then the optimum process param-eters were drawn. In enzymic hydrolysis, the optimum conditions were: 0.2 percent concentration of neutral protease,hydrolysis temperature 35℃,hydrolysis time 1h and the liquid to solid ratio 6:1.Under thes conditions, the product with 74.93 precent of crude fiber was obtained. Acid hydrolysis was not fit for the manufacture of dietary fiber acording to the qualityof final product. The optimum parameters of alkali dissolution were: 1.0 percent of sodium hydroxide, the liquid to solid ratio6:1, and cooking time 1h. Under these conditions, the final product of 90.42 percent of crude fiber was produced.

Key words: soy hull, dietary fiber, neutral protease, alkali cooking