Abstract
We worked out three different procedures to determine thiothiamine in acidic aqueous extracts of natural foodstuffs in the presence of thiothiamine. Thiothiamine is oxidized into thiochrome by either (1) alkaline benzoyl peroxide or (2) cyanogen bromide at pH 3.5 to avoide thiochrome-formation from thiamine, then the thiochrome formed is estimated fluorometrically. The third method, microbiological assay of thiamine by Lactobacillus fermenti before and after SO_2-treatments, which converts thiothiamine into thiamine, of the extracts at pH 4.5,will indicate the existence of thiothiamine, if the thiamine values after the treatment is greater than that before. Among 14 kinds of vegetables investigated, thiothiamine was detected in onions, Welsh onions, scallions, cabbage and Brussels spronts by benzoyl peroxide method. Existence of thiothiamine was only confirmed by microbiological assays in onions and scallions, while it failed in Welsh onions, cabbages and Brussel sprouts. Cyanogen bromide method (2) applied to onions and cabbages showed both positive.
