Distribution of Trypsin Inhibitors during Processing of Soybean Sprout

Abstract

Soybean sprouts are used commonly as a nutritional food material in Japan. Seeds of soybean contain several kinds of trypsin inhibitor(TI). In order to know the periodical changes of TI activity in soybean sprouts during germination, seeds of soybean were germinated or 6 days and TI activity in cotyledon and axis, was determined. (1) TI activity in soybean sprouts was 67.1mg corresponding to 80-85% of that of soaked soybean. More than 99% of TI activity of soybean sprouts existed in cotlyedon and the rest was contained in axis. TI activity in cotyledon and axis at different stages of germination were determined. It was 70.2mg in cotyledon and 14.3mg in axis after 2 days of germination, 64.6mg and 0.83mg after 4 days of germination. Cotyledon contained 73.7mg of its activity but axis did not show any TI activity after 9 days of germination. The activity of TI is expressed as mg of TI in one gram of fresh soybean sprouts. (2) TI in soybean seed and soybean sprouts (cotyledon and axis) was fractionated by gel filtration with Sephadex G-75. TI in soybean seeds and cotyledon was fractionated into 2 peaks, TI in axis after germination for 2 days showed only one peak. However 2 peaks were observed in FI from an axis after germination for 4 days and seemed to be separated from TI of 2 day-old axis. (3) TI peaks obtained by gel filtration were further fractionated by chromatography on a column of DEAE-cellulose. Main TI was shown to be 8 peaks. TI in cotyledon of soybean sprouts became difficult to be separated clearly due to close distance of each peak with increase of germination days. TI in axis was only one peak for 2 days of germination but it become 2 peaks for 4 days. (4) Changes of TI activity in soybean sprouts by heating were studied TI activity in cotyledon was inactivated compleaty by treatment with boiling water for 5min, but TI activity in axis was still remained.