THIOCYANATE ION, A HYDROLYSIS PRODUCT OF GLUCOSINOLATES FROM RAPE AND MUSTARD SEED

Seed meals from commercial cultivars and breeding lines of Brassica napus and B. campestris rapeseed and B. juncea mustard, when incubated with a yellow mustard (B. hirta) myrosinase isolate, released between 5.4 and 13.1 μmoles of thiocyanate ion per gram of oil-free meal. Low glucosinolate rapeseed cultivars released amounts (8.6–11.4 μmoles) similar to that released by normal glucosinolate cultivars (10.1–13.1 μmoles). Mustard cultivars released less thiocyanate ion (5.4–6.9 μmoles). Stoichiometric agreement between analysis for glucose, sulphate and the combined isothiocyanates and thiocyanate ion released from aqueous extracts of B. napus cv. Tower meal which had been incubated with the myrosinase isolate indicated that in addition to isothiocyanates, thiocyanate ion is a product of glucosinolate hydrolysis. Thus the indirect determination of the glucosinolate content of rapeseed and brown or Oriental mustard seed by analysis for the isothiocyanate hydrolysis products should be complemented by analysis for thiocyanate ion.