Influence Of Brewing Factors On Anthocyanins Derivatives Vitisins And Color Quality In Dry Red Wine

Color is an important indicator for evaluating the quality of red wine, the major compounds that are responsible for this color in wines are the anthocyanin pigments. The color of wine is determined mainly by the composition, concentration and stability of anthocyanins. The vitisins are the most studied pyranoanthocyanin family, they have multiple spectroscopic features. Meanwhile, vitisins are more stable than grape anthocyanins in respects of discoloration by SO2, and color loss due to high p H. Also, oxidative degradation during fermentation, contributes to the overall color of aged red wines.The sample wines in this study were young red wines made from Cabernet Gernischt grapes grown in Gansu Hexi Corridor. The goals of this work were to study the formation of the vitisins in red wines after the addition of the precursor molecules pyruvic acid and acetaldehyde, and to analyze the ensuing loss of total and monomeric anthocyanins. Meanwhile, the CIELAB parameters of sample wines which were added pyruvic acid and acetaldehyde at different stages of fermentation were assessed during the aging process. Eventually, the influence of brewing factors( yeast strains, p H, temperature and SO2)on Vitisins in red wines were studied. Results showed that:1. After the addition of acetaldehyde and pyruvic acid, the concentration of stable pigments vitisins in sample wines was significantly increased, while the content of total anthocyanins and M3 G did not change notablely.2. During the aging process, the concentration of total anthocyanin and M3 G decreased siginificantly, after 4 months in the bottles, approximately 80% of above had lost, while the content of vitisins decreased slightly(less than a loss of 25%). Compared to the control wine, the degradation rate of total anthocyanin and M3 G in pyruvic acid-and acetaldehyde-treated wines were slightly slower.3. After 6 months in the bottles, the a * value and Cab values of pyruvic acid and acetaldehyde treated wines were higher than the control wines, the L * value were lower than the contralto wines,which indicated that red hue, color degree and brightness of treated wines were higher than the control wines, Vitisins contribute effectively to the color quality of aged red wines.4. The contention of vitisins in EC1118 samples were highest and reached the highest content of Vitisin A and Vitisin B at the sixth day of fermentation.5. The concentration of vitisins as an evaluation index, combined single-factor experiments and response surface methodology, and recursive model was built,the optimum vinification parameters were: SO2 content 58.89 mg/L,fermentative temperature 26.57 ?, p H 3.92.In the process of winemaking, the selection of yeast strains that produce high levels of pyruvate and acetaldehyde could provide more stable pigments vitisins to wines, and improved the quality of color in aged wines. In addition, the yeast's ability of producing acetaldehyde and pyruvic acid was improved by regulating the addition amount of SO2, fermentation temperature and p H, which effectively increased the amount of vitisins formed in red wines.