Emission of volatile organic compounds from healthy and diseased onions
In this study, onions were selected from a sorting machine and divided into three groups, i.e., heathy onions, soft-rot onions, and Penicillium-infected onions, by visual and tactical judgement. For each of the groups, consumption of O2 and emission of CO2 were tested in closed jars. Besides, volatile organic compounds (VOCs) from healthy and diseased onions were sampled by solid-phase microextraction (SPME) and analyzed on GC-MS. The results showed that healthy and soft-rot onions had lower respiration rate than Penicillium-infected onions. Also the concentration of total VOCs was higher from soft-rot onions than from healthy onions and Penicillium-infected onions. Ten compounds were selected to describe differences in the VOC profiles between samples. These were ethanol, 1-propanol, 1-propanethiol, acetic acid, (E)-1-(methylthio)-1-propene, 1-(methylthio)-propane, dimethyl disulphide, 3-methyl-1-butanol, styrene, and methyl propyl disulphide. The levels of all ten compounds from the soft-rot onions and six from the Penicillium-infected onions were significantly different (P≤0.05) from the levels of the healthy onions. The soft-rot onions had high levels of ethanol, 1-propanol, 1-propanethiol, acetic acid and methyl propyl disulphide as compared to the healthy and Penicillium-infected onions. 3-methyl-1-butanol was specific to the soft-rot sample, while styrene was specific to soft-rot and Penicillium-infected onions.
Wang, A., Casadei, F., Johansen, A., Bukman, H. and Edelenbos, M. (2016). Emission of volatile organic compounds from healthy and diseased onions. Acta Hortic. 1144, 333-340
VOCs, Allium cepa, storage disease, fungi, GCMS, SPME