The work in this project is concerned with the headspace analysis of potato volatiles. In the context of the thesis, the term potato volatiles deals with the headspace volatiles that are naturally evolved by raw potato tubers, and the anthropogenic volatile sprout suppressant chemicals that are applied to stored potato tubers. Both aspects of potato volatiles were investigated and consequently this thesis is divided into two sections: Section 1 deals with the headspace analysis of the volatiles that are produced by raw potato tubers; Section 2 deals with the headspace analysis of two widely used commercial potato sprout suppressants. After harvesting, potato tubers undergo a period of dormancy which is defined as the time when the tuber buds are not growing: when dormancy is broken, the buds grow and elongate into sprouts. The mechanism of tuber dormancy is extremely complex, and the transition from the dormant to non-dormant state is associated with several physiological changes in the composition of the tuber. The first section, Section 1, of the project is an account of the investigations of the volatile compounds that are naturally evolved by raw potato tubers, in relation to the question of tuber dormancy. It has been shown that the volatiles produced by dormant potato tubers have sprout suppressant properties, thereby delaying the breaking of tuber dormancy (Burton, W. G., 1952), (Burton, W. G., Meigh, D. F., 1971). Further to this, it has been shown that the dimethylnaphthalene class of compounds is present in raw potato tubers and has been shown to possess potent sprout suppressant properties Neigh, D. F., et al, 1973), (Beveridge, J. 1980). However, it was thought that dormant potato tubers evolved volatiles, apart from the dimethylnaphthalenes, that had sprout suppressant properties. The aim of the project was the isolation and identification of the headspace volatiles that are naturally evolved by raw potato tubers and to relate these volatiles to tuber dormancy. The bulk of the work was taken up with the development of the analytical techniques for the isolation and separation of raw tuber headspace volatiles. Various systems were tested for the containment and separation of the headspace volatiles, from the outset the porous polymer adsorbent Tenax G. C. was used to trap the headspace volatiles, and high resolution gas chromatography using capillary columns was used for their separation. Three systems were developed for sampling: the first using an aluminium tank proved to be unsuitable due to background volatiles arising from the tank, the second and third which were constructed from glass and PTFE were found to be successful from the point of view of isolating a sample of potato tuber volatiles free from background volatiles. These two systems were used to study the headspace volatiles produced by sprouted and dormant potato tubers and to relate the breaking of dormancy to any changes in the volatiles produced. In addition, a gas chromatographic system was developed for the transfer of volatiles adsorbed on a Tenax G. C. precolumn into a capillary column, the final system adopted involved the thermal desorption of the volatiles from the Tenax G. C. into a small volume cold trap to concentrate the volatiles into a small volume and then a rapid reheat of the cold trap for the introduction of the volatiles into the capillary column.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:234838 |
| Date | January 1984 |
| Creators | Boyd, William David |
| Publisher | University of Glasgow |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://theses.gla.ac.uk/4394/ |
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