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

Sensors

Mette Marie Løkke²  Merete Edelenbos¹  Erik Larsen¹ 

[1] Department of Food Science, Aarhus University, Kirstinebjergvej 10, Aarslev DK-5792, Denmark; E-Mails:;Department of Engineering, Aarhus University, Blichers Allé 20, P.O. Box 50, Tjele DK-8830, Denmark; E-Mail:

关键词: PTR-MS;    real time monitoring;    volatile organic compounds;    Allium cepa L;   

DOI  :  10.3390/s121216060

来源: mdpi

【 摘 要 】

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.

【 授权许可】

CC BY   
© 2012 by the authors; licensee MDPI, Basel, Switzerland