Metabolite profiling using GC-MS to study core breakdown in relationship to biochemical changes during long-term storage of pears
Franck C.; Lammertyn J. and Nicolai B.M
5th International Postharvest Symposium . Volume of Abstract . Verona, Italy 6-11 June 2004, p.101
2004
บทคัดย่อ
Metabolite profiling using GC-MS to study core breakdown in relationship to biochemical changes during long-term storage of pears
‘Conference’ pears are susceptible to core breakdown, characterised by internal browning and cavities. Nowadays, growers apply certain postharvest treatments in order to minimise this disorder. However, the biochemical background of physiological storage disorders is still not fully understood. The objectives of this study were (1) to reveal biochemical differences between two cultivars with different susceptibility, (2) to investigate the characteristics of brown and sound tissue and (3) to study the effect of four different controlled atmosphere (CA) conditions during long-term storage. To induce core breakdown, pears (‘Conference’ and ‘Doyenne’) were stored immediately after harvest at 1% O
2, 10% CO
2. To study the effect of CA conditions, pears were stored under four different CA conditions. After tissue homogenisation, MeOH extraction and drying, the residues were derivatized with methoxyamine and MSTFA. GC-MS analysis was carried out using a SPB-50 column (Supelco). Each sample was injected with two different GC methods to optimise detection of sugars and lowly concentrated compounds. Multivariate statistics were used to analyse the data.
Brown-induced ‘Conference’ pears are characterised by fumarate, which was not found in ‘Doyenne’ pears (stored under similar conditions). The latter cultivar is richer in succinate and malate. Brown tissue differed from sound tissue by different sugar ratios, lower acid concentrations and the appearance of fumarate. Comparison of different CA storage conditions revealed that succinate accumulates in fruits exposed to high CO2 conditions, whereas its concentration is zero in low CO2 conditions. The O2 concentration seems mainly to affect the sugar metabolism: more disaccharids were found in low O2 conditions, the high O2 conditions contained more C5 sugars. From these results, there is evidence that high CO2 conditions block succinate dehydrogenase and that fumarase is inhibited in brown tissue, resulting in fumarate accumulation and malate deprivation.