Decomposition of sinigrin by methanol/ammonia/water treatment in model systems and mustard (Brassica nigra L.) seed meal

Sinigrin (allylglucosinolate) was stored at 20 degrees C, 40 degrees C, and 60 degrees C in solutions containing 10% ammonia in 95% methanol (CH3OH/NH 3/H2O), The individual samples were analyzed for their contents of sinigrin , its decomposition product allyl isothiocyanate (AITC) and other reaction products. The major reaction products were allyl thiourea, methyl ester of N-allyl thiocarbamoyl acid and allyl cyanide. A newly identified decomposit ion product of sinigrin was ethyl-cyanide. Defatted Brassica nigra seed mea l was treated by the CH3OH/NH3/H2O mixture to simulate the procedure used f or rape and mustard seed meal detoxification. Suspensions of the meal in th e above mixture of solvents were heated at 20 degrees C, 40 degrees C and 6 0 degrees C, respectively. The major reaction products were the same as tho se arising from sinigrin. Minor products identified were 4-hydroxybenzyl is othiocyanate formed from sinalbin and 2-hydroxy-butenyl cyanide which arise s from progoitrin. In all cases, AITC was very rapidly decomposed. Mechanis ms explaining sinigrin decomposition are presented and discussed.