Abstract

The main objective of this project was to see if volatile organic compounds could be identified in unprocessed vegetables. Once the identification of possible marker compounds was completed, a variety of vegetables with either disease, damage or physiological changes associated with aging were analysed.

Potatoes, onions and broccoli were analysed, these vegetables were chosen by some of the project’s co-funders as being economically important

The sample of vegetable was placed in an airtight container and the sample was allowed to equilibrate at room temperature for 45 minutes, then a solid phase microextraction fibre (SPME) was inserted through the valve and the fibre exposed for 50 minutes. The fibre was then retracted into its holder prior to analysis using a Gas Chromatograph/Mass Spectrometer (GC/MS). The sample was then analysed using the GC/MS and the peaks identified using the built-in library in the instrument software.

In the case of potatoes, no changes in volatiles were observed during the sprouting process or in the case of physical damage. However, changes were identified in the case of potatoes with a variety of diseases, these changes in volatiles were the same regardless of the disease present. The compounds found for potatoes were trimethylamine, 2-butanone, 2,3-butanedione, 3-hydroxy-2-butanone and 2,3-butanediol.

The analysis of onions showed differences in the volatiles between uninfected/control samples and those with thick neck, basal rot, internal rot and neck rot. The compounds found were 1-propanethiol, methyl propyl sulphide, methyl propyl disulphide and dipropyl sulphide However, the change in volatiles could not be used to differentiate between the different rots.

For broccoli differences were found between control and samples with wet rot. The compounds found included dimethyl sulphide, dimethyl disulphide, dimethyl trisulphide and 1-undecene. The differences were then used to investigate these changes in volatiles in relation to use by dates of pre-packaged broccoli, this investigation showed none of the marker compounds at significant levels for those samples analysed before or on their use by date.