| The maturity of wine grapes is one of the important factors affecting the quality of wine.Because of its regional,variety,year and other differences,it is difficult to form a unified standard.In recent years,domestic researchers have established a maturity control system including fruit juice sugar and acid index and skin seed polyphenol index for the main red wine grape varieties planted in western regions.Jieshishan area is the main producing area of dry red wine in the eastern part of China.The harvesting date of wine grape is determined mainly based on sugar and acid index and winemaker’s experience,and there is no complete maturity index evaluation system.This subject tracks the precipitation at fruit maturity stage in the Jieshishan area in 2021,determines basic physicochemical index,organic acid indicators and polyphenol indicators in the ripening process of ’Marselan’ and’Cabernet Sauvignon’,analyzes the components and sensory quality of dry red wine made in different harvesting periods,and establishes the red wine grape maturity index system in the Jieshishan area in rainy years.It provides theoretical basis for guiding timely harvesting in this producing area.The results show that:(1)Changes in fruit quality indicators of ’Marselan’ and ’Cabernet Sauvignon’during ripening.The contents of soluble solids,reducing sugar and sugar-acid ratio gradually increased,the total acid content continued to decrease,and the p H value slowly increased at the ripening stage.The tartaric acid content of ’Marselan’ tended to be stable in general,while that of ’Cabernet Sauvignon’ showed a wavy downward trend,and the malic acid content of both varieties showed a downward trend.Anthocyanins,total phenols,tannins,flavonoids and flavanols in grape skins had basically the same changing trend during the ripening period,which increased in the early stage and decreased or tended to be stable in the later stage.However,the changes of polyphenol content in grape seeds were quite different,especially the tannins in seeds showed a jump increase in the middle and late ripening stage.The heavy rainfall at maturity stage had different effects on all monitoring indexes,significantly reduced reducing sugar content and p H,delayed anthocyanin accumulation,increased tannin content in seeds,reduced polyphenols content in fruit peel,and delayed the increase of soluble solid to sugar-acid ratio,but the acid drop was stable.(2)The influence of different harvest period on the quality of dry red wine.As the harvest period went on,the polyphenols in dry red wine showed an increasing trend.The brew dry red wine of ’Marselan’ harvested on October 2,when stored for 9months,had the highest chroma,anthocyanin content,a* value and sensory score,the lowest p H,L* value,b* value and hue,and the higher contents of total acids,total phenols,tannins,flavonoids and flavanols.The brew dry red wine of ’Cabernet Sauvignon’ harvested on 28 September had the highest total acid,chroma,anthocyanin content,a* value and sensory score,the lowest p H,b* value and hue,and low total phenol,tannin,flavonoid and flavanol content.In rainy years,the best harvest dates for ’Marselan’ and ’Cabernet Sauvignon’ are October 2 and September28,respectively.(3)Establishment of ripeness index system for red wine grapes in rainy years.Based on the fruit indexes of different sampling periods in 2021,by using correlation,principal component and weight analysis methods,was used to establish the maturity index system of ’Marselan’ and ’Cabernet Sauvignon’ in the Jieshishan area in rainy years.The primary,secondary and tertiary indexes of ’Marselan’ maturity index system were sugar to acid ratio,seed tannin and skin tannin,with values ranging from35.68～42.06,16.03～20.28 mg/g and 1.99～2.35 mg/g,respectively.The primary,secondary and tertiary indexes of the maturity index system of ’Cabernet Sauvignon’are the total peel phenol,seed flavanol and skin flavanols,with values ranging from20.56～20.72 mg/g,51.39～62.11 mg/g and 4.09～13.98 mg/g,respectively. |
PDF Full Text Request