The accumulation of chlorophylls and glycoalkaloids in stored tubers.

Edwards, E.J., 1997. The accumulation of chlorophylls and glycoalkaloids in stored tubers. PhD, Nottingham Trent University.

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Exposure to light causes potato tubers to green, due to the conversion of amyloplasts to chloroplasts (Anstis and Northcote, 1972), and accumulate toxic steroidal glycoalkaloids (Conner, 1937). The two major alkaloids, comprising 95% of the total (TGA) are α-solanine and α-chaconine (Olsson, 1989). The consumption of potatoes with high TGA concentrations can cause illness and even death (Morris and Lee, 1984).

This study reports the successful adaptation of leaf Chi analysis methods to potato tubers. Existing HPLC methods of TGA analysis have been critically examined and a number of problems have been addressed. This combined with the use of a new SPE sorbent has resulted in sample recoveries of 93 and 99% for α-solanine and α-chaconine respectively. The reliability and reproducibility of these methods allow them to be used routinely.

Exposure of potato tubers to low PPFD at various temperatures has shown that even at a PPFD of 12 μmol photons m-2 s-1 tubers will accumulate detectable Chi within 48 hr. It has also been demonstrated that storage at 5°C will delay the onset of greening and greatly reduce its severity. Long term storage of tubers reduced the potential for light-induced accumulation of TGA but did not have any significant effect on Chi synthesis. The extent of both greening and TGA accumulation were dependant on cultivar choice. Artificial neural networks were used to model the data produced by these experiments and were shown to closely follow the actual data. These could then be used to predict tuber response to specific storage and light exposure

Preliminary studies on the physiology of greening demonstrated that the accumulation of Chi and TGA were not biosynthetically connected. Also, carotenoid composition during greening was shown to change markedly, including the synthesis of carotenoids not present in unexposed tubers and results indicated that greened tubers are capable of fixing atmospheric CO2.

Item Type: Thesis
Creators: Edwards, E.J.
Date: 1997
ISBN: 9781369313079
Rights: This copy of the thesis has been supplied on condition that anyone who consults it is understood to recognise that its copyright rests with the author and that no quotation from the thesis and no information from it may be published without the authors prior written consent.
Divisions: Schools > School of Animal, Rural and Environmental Sciences
Record created by: Jeremy Silvester
Date Added: 28 Aug 2020 16:23
Last Modified: 15 Jun 2023 09:55

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