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Sensors 2012, 12(12), 16060-16076; doi:10.3390/s121216060

Investigation of Volatiles Emitted from Freshly Cut Onions (Allium cepa L.) by Real Time Proton-Transfer Reaction-Mass Spectrometry (PTR-MS)

1
Department of Engineering, Aarhus University, Blichers Allé 20, P.O. Box 50, Tjele DK-8830, Denmark
2
Department of Food Science, Aarhus University, Kirstinebjergvej 10, Aarslev DK-5792, Denmark
*
Author to whom correspondence should be addressed.
Received: 31 August 2012 / Revised: 30 October 2012 / Accepted: 8 November 2012 / Published: 22 November 2012
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Abstract

Volatile organic compounds (VOCs) in cut onions (Allium cepa L.) were continuously measured by PTR-MS during the first 120 min after cutting. The headspace composition changed rapidly due to the very reactive volatile sulfurous compounds emitted from onion tissue after cell disruption. Mass spectral signals corresponding to propanethial S-oxide (the lachrymatory factor) and breakdown products of this compound dominated 0–10 min after cutting. Subsequently, propanethiol and dipropyl disulfide predominantly appeared, together with traces of thiosulfinates. The concentrations of these compounds reached a maximum at 60 min after cutting. Propanethiol was present in highest concentrations and had an odor activity value 20 times higher than dipropyl disulfide. Thus, propanethiol is suggested to be the main source of the characteristic onion odor. Monitoring the rapid changes of VOCs in the headspace of cut onion necessitates a high time resolution, and PTR-MS is demonstrated to be a very suitable method for monitoring the headspace of freshly cut onions directly after cutting without extraction or pre-concentration. View Full-Text
Keywords: PTR-MS; real time monitoring; volatile organic compounds; Allium cepa L. PTR-MS; real time monitoring; volatile organic compounds; Allium cepa L.
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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MDPI and ACS Style

Løkke, M.M.; Edelenbos, M.; Larsen, E.; Feilberg, A. Investigation of Volatiles Emitted from Freshly Cut Onions (Allium cepa L.) by Real Time Proton-Transfer Reaction-Mass Spectrometry (PTR-MS). Sensors 2012, 12, 16060-16076.

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