BENZYLGLUCOSINOLATE DEGRADATION IN HEAT-TREATED LEPIDIUM SATIVUM SEEDS AND DETECTION OF A THIOCYANATE-FORMING FACTOR

Article abstract of DOI:10.1016/S0031-9422(00)82405-X

Lepidium sativum seeds were dry heated at 125 deg C for varying periods, and also for 30 min at various temperatures.Autolysates were then analysed for benzylglucosinolate degradation products.Whilst heating for 4 hr 20 min at 125 deg C was sufficient to prevent formation of benzyl thiocyanate, just over 7.5 hr at 125 deg C was required before benzyl isothiocyanate also ceased to be produced.This indicates the presence of a discrete, thiocyanate-forming factor in L. sativum seeds, separate from thioglucosidase.After 7.5 hr at 125 deg C, benzyl cyanide continued to be formed, proving that it can be obtained (in relatively small amounts) directly from the glucosinolate even without the influence of any thioglucosidase.In general, isothiocyanate was the more favoured product of glucosinolate degradation following heat treatment of seeds, until the point of thioglucosidase inactivation was approached when nitrile formation took over.It is suggested that the thiocyanate-forming-factor is an isomerase causing Z-E isomerization of the glucosinolate aglucone, but that only those glucosinolates capable of forming particularly stable cations are then able to undergo E-aglucone rearrangement to thiocyanate. Key Word Index- Lepidium sativum; Cruciferae; cress; glucosinolate degradation; thiocyanate.