|Cohen, Seth - OREGON STATE UNIVERSITY|
|Kennedy, James - OREGON STATE UNIVERSITY|
Submitted to: In Vino Analytica Scientia
Publication Type: Abstract Only
Publication Acceptance Date: September 1, 2007
Publication Date: September 30, 2007
Citation: Cohen, S.D., Tarara, J.M., Ferguson, J.C., Kennedy, J.A. 2007. Assessing the impact of temperature on grape phenolic metabolism using multiple chromatographic approaches. In Vino Analytica Scientia 2007 Proceedings. Technical Abstract: This study assessed the impact of fruit temperature on the phenolic metabolism of grape berries (Vitis vinifera L. cv. Merlot) grown under field conditions with controlled exposure to sunlight. Individual cluster temperatures were manipulated in situ. Diurnal temperature fluctuation was damped by daytime cooling and nighttime heating of clusters. Daytime-only and nighttime-only temperature controls were applied for comparison. Berry skin temperatures were recorded continuously for each sample to compare against chemical data. Samples collected at veraison indicated that damping diurnal temperature fluctuation advanced the onset of the ripening process. Those berries were larger (double-damped: 0.753±0.015 g/berry vs control: 0.512±0.034) and more colored than all others. Development of phenolic metabolites was followed by two reversed-phase HPLC methods and size exclusion chromatography. These methods provided information on anthocyanins, proanthocyanidins, flavonols, flavan-3-ol monomers and polymeric material. Treatments yielded variation in the production of phenolic metabolites. Dampening diurnal temperature fluctuation reduced proanthocyanidin mDP (double-damped: 21.8±1.0 vs control: 28.0±1.7) compared to other treatments. Proanthocyanidin accumulation at veraison showed a linear relationship to total heat summation over the developmental period with nighttime heating yielding the highest concentration and daytime cooling yielding the lowest (night-heat: 1.46±0.13 mg/berry vs day-cool: 0.97±0.09). Dampening diurnal temperature fluctuation had a marked effect on rate of fruit development whereas total heat summation had more of an effect on phenolic metabolism alone. Analytical data from this study provides insight regarding the direct effect of temperature on phenolic metabolism and an indirect effect possibly attributed to manipulation of the growth cycle.