Content and distribution of pungent components in several cultivars and lines of wasabi (Wasabia japonica Matsum.)

In order to establish a simple and easy method for evaluating the contents of pungent components in rhizomes of wasabi, we investigated the relationships between the contents of allylisothiocyanate and other compounds associated with its release i.e., sinigrin, ascorbic acid and myrosinase activity with several cultivars and lines. The histological distributions of these compounds in rhizome were also examined. The results obtained were as follows; 1. The contents of allylisothiocyanate in rhizomes showed a considerable differences among cultivars and lines tested, and tended to be lower in those forming thicker rhizomes. 2. The amount of allylisothiocyanate released was proportional with that of its glucosinolate sinigrin contained in rhizomes. No relationship was, however, observed between the contents of allylisothiocyanate and ascorbic acid or myrosinase activity. It was suggested that the sinigrin contents could be used as a criterion for evaluating the amounts of pungent components contained in wasabi rhizomes harvested at the same time. 3. Allylisothiocyanate and sinigrin were contained at higher concentrations in outer layers of rhizome e.g., epidermis, cortex and vascular bundles, but lower in central portion e.g. pith. The myrosinase activity was higher in the vascular bundles than other tissues, it being negligible in pith. 4. It was clarified that the total sinigrin content of whole rhizome could be well evaluated by its content in the longitudinally and transversely central portion of rhizome.