Metabolic profiling using GC-MS to study biochemical changes during long-term storage of pears

Even though the storage disorder core breakdown in 'Conference' pears can be controlled quite well nowadays, its biochemical background remains unclear. In order to induce biochemical changes in pear fruit tissue, (1) late-harvested 'Conference' pears were stored at -1 degrees C under browning-inducing conditions (1% O-2, 10% CO2) and (2) optimally picked pears were stored at -1 degrees C under following CA conditions: 2.5% O-2, 0.7% CO2; 15% O-2, 0.7% CO2; 2.5% O-2, 5% CO2; 2.5% O-2, 5% CO2. A simultaneous analysis of amino acids, organic acids and sugars was carried out using GC-MS. Multivariate statistics were used to reduce the complexity of the profiling data. All storage conditions were clearly separated. It was found that malic acid, succinic acid and furnaric acid were the most crucial metabolites, explaining most of the variance. Brown tissue is characterised by fumaric acid accumulation and malic and succinic acid depletion. High CO2 conditions were characterised by enhanced levels of succinic acid whereas malic acid depletes. Depending on their degradation pathway and biosynthetic group, the concentration of certain amino acids increased while that of others decreased. An attempt was made to combine the biochemical observation with the known biochemistry of the Krebs cycle and its related pathways. Although core breakdown is considered as a CO2-injury, the biochemical profiles of brown pears were not equal to those of sound pears in high CO2 conditions.