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

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

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Received: 31 August 2012; in revised form: 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.
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 which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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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.

AMA Style

Løkke MM, 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(12):16060-16076.

Chicago/Turabian Style

Løkke, Mette Marie; Edelenbos, Merete; Larsen, Erik; Feilberg, Anders. 2012. "Investigation of Volatiles Emitted from Freshly Cut Onions (Allium cepa L.) by Real Time Proton-Transfer Reaction-Mass Spectrometry (PTR-MS)." Sensors 12, no. 12: 16060-16076.


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