Allium odors were re-examined to determine whether or not they contain degradation compounds of thiosulfinates. Garlic (Allium sativum), leek (Allium porrum) and onion (Allium cepa) were investigated using cryotrapping and direct injection of aqueous solutions of the samples into a high-performance liquid chromatograph (HPLC), with a diode-array detector, coupled to a mass spectrometer (MS). Various commercial systems which couple HPLC to tandem MS, but using different ionization systems, were compared. Best results were obtained with atmospheric pressure chemical ionization although degradation of certain thiosulfinates was observed. Depending on the HPLC/MS interface, thiosulfinates formed dimers in variable quantity and this reaction could be used to differentiate isomeric 1-propenyl and 2-propenyl thiosulfinates. Some unresolved isomers were identified by their fragment ions. No disulfides or other rearrangement products were observed and it was concluded that Allium odors contain only thiopropanal S-oxide and thiosulfinates as sulfur volatiles.
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Ferary et al. (1996) studied this question.