Abstract:
Objective Improvement on quality of wine made from Ziqiu wild grapes southern grapes was explored through vine fertilization and vinification optimization.
Method Ziqiu wild grape vines were foliar-sprayed with GS-1 solutions in various concentrations 3 times after the grape color began to change. Application concentration was selected to maximize the contents of proanthocyanidins, free anthocyanins, total phenolics, and total flavonoids in the grapes. Contents of total acid and sugar in the grapes were monitored regularly and ratio of sugar to acid (ripeness coefficient) calculated to determine the time for harvesting and processing. Sensory evaluation and physiochemical parameters on the wine were used to optimize the inoculum species and amount, temperature, and time of the fermentation process in a single factor test followed by an orthogonal experiment.
Result (1) Late September, when grape maturity coefficient, M, reached over 21, was the time for harvesting and starting fermentation. (2) By spraying 300x dilution of GS-1 on the vines, the harvested grapes produced significantly increased amount of key nutrients in the wine. For instance, total sugar, proanthocyanidins, free anthocyanins, total phenolics, and total flavonoids rose 3.74%, 26.99%, 35.41%, 13.91%, and 24.12%, respectively, over control. (3) The optimized fermentation applied JP2 Saccharomyces cerevisiae as the inoculum at 1% to culture at 24 ℃ for 10 d.
Conclusion The Ziqiu wild grapes grown on the vines sprayed with GS-1 and picked at the time closely scrutinized by the fruit maturity coefficient produced a wine made by the optimized process with significantly improved nutritional and sensory quality.
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