Abstract
Regular intake of vegetables suppresses the risk of lifestyle-related diseases. In Japan, a large amount of cruciferous vegetables that contain glucosinolates are consumed in cooked or pickled form. Glucosinolates are hydrolysed to isothiocyanates in plants by the enzyme myrosinase, which is released by tissue damage. Isothiocyanates have characteristic flavours and can inhibit carcinogenesis in some cases. In this study, we investigated the effects of NaCl and ascorbic acid concentration on myrosinase activity in vitro. Maximum myrosinase activity was observed for 1% NaCl or 0.1% ascorbic acid, although myrosinase activity was suppressed by a combination of NaCl and ascorbic acid. The degree of suppression of myrosinase activity decreased as the concentration of ascorbic acid increased.
We prepared lightly pickled turnip and Chinese cabbage with final NaCl concentrations of 1%, 2%, and 3% to determine the effect of NaCl on isothiocyanate formation in pickles. 3-Butenyl, 4-pentenyl, and phenethyl isothiocyanate were detected by gas chromatography-mass spectrometry analyses; these compounds were formed in the highest amounts at 3% NaCl in both types of pickles. Moreover, the addition of 0.4% ascorbic acid increased the formation of isothiocyanate by 1.4-1.6 times compared with the control in both types of pickles. In sensory evaluation, panellists preferred the pickles with 2% NaCl.
