以脱脂豆粕为原料，通过“碱提酸沉”法制备大豆分离蛋白，经正交实验确定的最适条件是碱液萃取温度为50 ℃、碱液萃取pH值为8、酸沉淀pH值为4.0。以所得的大豆分离蛋白为反应底物制备大豆胨并优化其制备工艺。结果表明，反应的最佳条件为：酶解温度为55 ℃，酶解pH值为7.5， 底物浓度为5%，E/S为16 g/kg。将按照此工艺条件制备出的大豆胨的各项理化指标与所购标准品相比，差异不大。氨基酸分析结果表明，大豆胨中必需氨基酸种类丰富齐全，可为微生物的生长提供丰富的营养。
Soybean protein isolate（SPI）was prepared from defatted soybean meal by alkali extraction and acid precipitation. The optimum condition was obtained by orthogonal experiment,and the alkali solution temperature was 50 ℃, alkali-soluble pH 8, acid precipitation pH 4.0. Soya peptone was prepared from SPI and the preparation techniques were optimized. The result showed that the optimal technical conditions were as follows: reaction temperature 55 ℃, pH value 7.5, substrate concentration 5% and E/S 16 g/kg. All physical and chemical indexes of the obtained soya peptone were similar to the purchased standards. The soya peptone was abundant in essential amino acids with complete varieties and was suitable for culture medium in the preparation of microorganism.