A Preliminary Study Of Wine Grape Maturity Index System In Qingtongxia, Ningxia Province

Grapes are the basis of wine, and the harvest time is the key to ensure the grapes quality. Consider the phenolics is important for determining the optimal harvest time. In this research, the Cabernet Sauvignon(CS), Merlot(ML) and Pinot Noir(PN) were chose as experimental material of Ningxia Qingtongxia in 2014. The sugar, acid, and phenolics of skins and seeds were determined during ripening. Meanwhile, the wine was produced, and the physicochemical composition and sensory characteristics were analysed. The correlations of grape physicochemical index, wine physicochemical index, and sensory quality were analysed using the SPSS, and chose the indexes which had important effects on the sensory quality to establish the maturity index system. This study provided a new direction to monitor the maturity and determine the optimal harvest time. The primary conclusions were as follows:(1) The total phenolics, anthocyanins, flavanols, flavonoids, and tannin content in grape skins of CS and ML, the anthocyanins and flavanols in PN skins, and the total phenolics in CS seeds increased during ripening. The total phenolics in PN skins and seeds, tannin in skins and seeds of CS, ML and PN, and flavonoids in CS and PN seeds decreased, also the flavanols in CS and PN decreased during ripening. While, the flavonoids in seeds of ML and PN in skins, and total phenolics in ML seeds had little changes.(2) The CS wine which had better aroma, mouthfeel, and quality was produced when the grapes were harvested in Oct. 2. The ML and PN wine which had better appearance, mouthfeel, and quality were produced when the grapes were harvested in Sep. 11.(3) In this research, the harvest index system was initially established. The first grade assessment indicator was sugar/acid, the second was tannin coefficient(ratio of tannin content in grape skins and seeds), and the third was anthocyanins content. Meanwhile, the values of indexes of CS, ML, and PN in Qingtongxia was decided. CS: The first grade assessment indicator was 29~30, the second was 0.50~0.60, the third was 18.00~20.50 mg/g. ML: The first was 29~40, the second was 0.60~0.75, the third was 13.50~14.50 mg/g. PN:The first was 24~30, the second was 0.40~0.90, the third was 3.40~7.10 mg/g.