| Quality and style of wine are determined by quality of grapes. Quality of grapes mainlydepends on grape varieties, region characteristics, climatic conditions, cultivation conditionsand maturity. Because of hot dry climate, significant difference in temperature between dayand night, drought, abundant sunshine in southern Xinjiang area, the grapes mature fast andhave high sugar content. One of the main factors restricting grape quality is low organic acidcontent,so stage of maturity is an important factor affecting the acidity in southernregions.Therefore, determing the appropriate stages of maturity is very important for thebalance of sugar and acid to obtain high-quality grapes.The trial in Fangxiang vineyard, Xinjiang Province used Cabernet Sauvignon grapes assample material by studying changes of the sugar content, pH, acid,sugar/acid,the total tannin,total polyphenols,total flavonoids,total anthocyanins,total monomer anthocyanidins, totalmono-phenol from different stages of maturity to understand the characteristics of winegrapes mature in hot regions, to reveal the impact of grape quality for different stages ofmaturity. The main research results were as follows:1. The total sugar content of Cabernet Sauvignon increased slowly after veraison. In lateSeptember total sugar rose up to254.49g·L-1which basically in line with "S" shaped curvecharacteristic trends.The pH value,sugar/acid,total sugar,total acid and stages of maturityshowed significant correlations each other. The pH value increased and total acid contentdecreased rapidly from13.25g·L-1to4.39g·L-1. Total sugar,sugar/acid,total acid showedsignificant correlations each other while they had significant negative correlations with thetotal acid. Sugar/acid gradually increased became mature up to20in August21st.All in all,physical and chemical composition of the grape and stages of maturity had significantcorrelations,so delay harvest could have imbalance between acidity and total sugar.2. In the stages of grape mature total tannins, total polyphenols and total flavonoids alldecreased slowly and increased slowly while tannins content decreased faster than totalpolyphenols and total flavonoids had the smallest change. The total anthocyanins, by contrasthad a slow decline after the first rise,and total monomer anthocyanidins fluctuated reducing further increase after the first increase and decrease. mono-phenols trends were quite different.This suggested that an appropriate delay harvest would help deepen the color of wine as wellas get more tannins and flavonoids to enhance the sense of the structure of the wine.3.After principal component analysis for all indexes,we got four main components whosecumulative contribution rate was up to93.065percent which fully reflected the overall qualityof Cabernet Sauvignon grapes harvested in different periods.Grape quality mainly wasinfluenced by total sugar, various monomers anthocyanins, flavonoids, various mono-phenolcontent. Overall quality of Cabernet Sauvignon grapes harvested in different rankingsfollowed by CS9-16, CS9-23, CS8-24, CS9-8, CS9-5, CS8-30, CS8-21, CS8-27, CS9-2,CS8-18. Since late harvest led to low acidity, it gave a negative impact on the quality of winegrapes, so we determine that between September5th and8th was the best time to harvestCabernet Sauvignon grapes combining the actual situation with statistical data. |
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