An evaluation of the role of amino acids in the processing quality of stored potato tubers

Brierley, E.R., 1994. An evaluation of the role of amino acids in the processing quality of stored potato tubers. PhD, Nottingham Trent University.

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Abstract

This study has been undertaken in order to assess the role of amino acids in determining the processing quality of stored potato tubers. Both the free amino acid content of tubers and possible factors regulating this pool size during prolonged storage were examined, their influence on the processing quality of 2 commercially important cultivars being ascertained over 4 consecutive storage periods.

Turnover of tuber proteins took place throughout storage, the net direction of nitrogen flow depending on the dormancy state of the tuber. As a consequence, free amino acid content was influenced by storage duration. Both cultivars demonstrated an increase of these metabolites during the latter part of storage, caused by an upturn of proteinase activity on the break of dormancy. This was possibly due to de novo synthesis of proteinases in particular a 47kDa monomeric enzyme of the aspartic proteinase catalytic class. A high proportion of amides in the free amino acid pool resulted from the activity of glutamine synthetase.

Turnover of proteins increased with storage temperature, although the net direction of nitrogen flux was temperature independent. Consequently, reconditioning regimes were ineffective at lowering free amino acid content, their effects on processing quality being due to the decrease of reducing sugars. When nitrogen flow exhibited a distinct direction this was enhanced by higher temperatures, the late-storage increase of free amino acids demonstrating temperature dependence in Pentland Dell due to greater proteinase activity at 10°C than 5°C. The accumulation of free amino acids, especially the amides, in Pentland Dell at 10°C corresponded with a deterioration of processing quality that could not be accounted for by reducing sugars alone. Despite being in excess with respect to reducing sugars, amino acids had a probable synergistic effect on fry colour production resulting in a darker fry colour per unit reducing sugar.

Item Type:	Thesis
Creators:	Brierley, E.R.
Date:	1994
ISBN:	9781369325508
Identifiers:	Number Type PQ10290301 Other
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 derived from it may be published without the author’s prior written consent.
Divisions:	Schools > School of Science and Technology
Record created by:	Linda Sullivan
Date Added:	05 Jul 2021 15:38
Last Modified:	20 Mar 2024 15:47
URI:	https://irep.ntu.ac.uk/id/eprint/43327

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