Study Of Maturity Control Indexes Of Major Red Wine Grapes From Qingtongxia City In Ningxia

Grape maturity is the key to determine grape quality which can ensure wine quality.Currently, the harvest time of wine grape is mainly determined by the sugar-acid ratios(M)without considering the polyphenols. However, the polyphenols are closely related with the color, flavor and the like of wine, and therefore, it is very important for evaluating grape maturity to glue them together. In this research, three major red grape varieties(Pinot Noir,Merlot and Cabernet Sauvignon) from Qingtongxia City in Ningxia province of China, were examined. The changes of phyto-chemical indexes and polyphenols contents were monitored during the grapes ripening. Meanwhile, quantitative descriptive analysis(QDA) was used for the wines sensory indexes to evaluate the resulting wines quality. Additionally, principal component analysis(PCA) was used for selecting the main polyphenols indexes for evaluating polyphenols maturity of the wine grapes, which could be applied to preliminarily establish the harvest indexes system of the three red grapes with M in this area. The main conclusions were as follows:(1) The reducing sugar contents and M of the three grape varieties increased, but their total acid contents decreased during the grapes ripening. The polyphenols contents in their skins increased first and then decreased during the berries ripening. The polyphenols contents in the seeds of Pinot Noir and Merlot decreased, but their contents in the seeds of Cabernet Sauvignon increased during the berries ripening. Meanwhile, the seeds had more the polyphenols contents than the skins.(2) When Pinot Noir and Merlot grapes were harvested on Sep. 12, their resulting wines(PW-3 and MW-3) all had better quality, when Cabernet Sauvignon grapes were harvested on Oct. 10, the resulting wines(CW-4) had better quality. Meanwhile, PW-3, MW-3 and CW-4had more the polyphenols contents.(3) The total anthocyanins in skins and the total polyphenols in seeds were selected by PCA and correlation analysis for evaluating the polyphenols maturity of Pinot Noir and Merlot, the total anthocyanins in skins and the total flavonoids in seeds were selected for evaluating the polyphenols maturity of Cabernet Sauvignon. Meanwhile, when the M, the total anthocyanins in skins and the total polyphenols in seeds of Pinot Noir and Merlot wererespectively 26.18±0.33~33.47±0.42, 5.27±0.04~7.80±0.14 mg/g, 67.09±0.90~69.55±2.86mg/g and 30.04±0.46~42.67±0.99, 12.58±0.35~15.71±0.24 mg/g, 55.78±1.79~72.96±1.65mg/g, the grapes and wines all had better quality. When the M, the total anthocyanins in skins and the total flavonoids in seeds of Cabernet Sauvignon were respectively 27.68±0.32~34.69±0.24, 12.22±0.08~14.07±0.02 mg/g and 41.64±0.10~53.62±1.45 mg/g, the grapes and wines all had better quality.