Effect of Different Harvest Dates on the Quality of Pinot Noir Grape and the Resulting Wine
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Abstract:
The quality of Pinot Noir grapes and the resulting wines was evaluated according to different harvest dates in this study. The grape samples were collected once every seven days after veraison to monitor the changes of physicochemical indices and polyphenol contents. In addition, quantitative descriptive analysis (QDA) was performed on the sensory indices of the wines prepared from the grapes collected at different harvest dates, to determine the optimum harvest date of Pinot Noir grape from Qingtongxia City in Ningxia. Principal components analysis (PCA) was performed on the polyphenol indices of the grapes collected at different harvest dates and the resulting wines, and the indices that had the most significant impact on their quality were screened out, which proved to be a simplified and practical approach. The results showed that the reducing sugar contents and the sugar-acid ratios increased and the total acid contents decreased continuously during the grape ripening. The polyphenol contents of both the skins and seeds showed an upward trend after the initial decrease. The results of QDA indicated that the sensory quality of the wines increased with a prolonged harvest date. The results of PCA showed that the total flavonoids of the seeds, total flavonoids of the skins, and total anthocyanins of the skins had the most significant impact on the quality of the grapes and wines. Moreover, when their contents were 52.02 ± 0.13 mg/g, 29.95 ± 0.28 mg/g, and 7.09 ± 0.02 mg/g, respectively, the polyphenolic maturity of the grapes and the quality of the wines were relatively good. This study can provide guidance for determination of the most suitable harvest date of Pinot Noir grapes in this region.
