Comparative Distribution of Volatile Aliphatic Disulfides Derived from Fresh and Dehydrated Onions

SUMMARY— Gas chromatographic determination of the volatiles from fresh “Sunspice” onions revealed that the principal disulfide present is di‐St‐propyl, followed in descending, order of concentration by n‐propyl allyl, methyl‐n‐propyl, methyl allyl, dimethyl, and diallyl. In dehydrated onions this order is markedly altered. Methyl‐n‐propyl is the principal disulfide, followed by dimethyl, methyl allyl, di‐n‐propyl, n‐propyl allyl, and diallyl. Quantitative estimates of the disulfide content of 53 lots of fresh onions were made and compared with analyses of dehydrated onions from comparable lot numbers. Loss of measured volatiles averaged 98%, while loss of disulfides was greater than 89%. The relationship of disulfides to onion flavor and a pungency ranking system based on these analyses are discussed.