CONTENTS OF PUNGENT PRINCIPLE IN ROOTS OF JAPANESE RADISH (RAPHANUS-SATIVUS L) CULTIVARS

The contents of 4-methylthio-3-butenyl isothiocyanate (MTB-ITC) in roots of Japanese radish (Raphanus sativus L.) were determined by gas chromatography to evaluate the relative pungency of cultivars. The relationship between the content of MTB-ITC and the taste of grated radish was also examined. The contents of MTB-ITC in more than half of the commercial cultivars ranged from 200 to 300-mu-mol/100 ml juice. Among the cultivars examined, 'Karami' showed the highest content of MTB-ITC, reaching as much as 1735-mu-mol/100 ml, followed by 'Shinshu-jidaikon' group of 400 approximately 700-mu-mol/100 ml. 'Ninengo' and 'Shiroagari' groups also exhibited relatively high content averaging more than 300-mu-mol/100 ml. On the contrary, 'Miyashige' group or Chinese cultivars contained the lowest level of MTB-ITC ranging from 100 to 200-mu-mol/100 ml. Coefficients of variance in MTB-ITC content among individual roots were 32 approximately 43% in old-type purebred cultivars, and 12 approximately 14% in recently-released F1 hybrid. A significant negative correlation (r = -0.789) was observed between the content of MTB-IT and the water content of the tissues among cultivars. The result of sensory evaluation on grated radish showed that a cultivar with higher content of MTB-ITC was proportionately more pungent, supporting the idea that this substance is the pungent principle in roots of Japanese radish.