20140808 Variation in tartaric and malic acid concentrations in grapevine berries
From Denise Dewey on August 5th, 2014
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Organic acids are important to the flavor of grapes and wine and aid in the prevention of microbial spoilage during fermentation, with tartaric acid and malic acid accounting for 90% of the acidity in grape berries. During post-veraison, malic acid begins breaking down and this breakdown may accelerate during the growing season with higher temperatures. The resulting decrease in acid increases the pH of the juice and, in Australia, tartaric acid is added to the juice at a considerable cost to lower the pH during winemaking.
The cost of adding tartaric acid during winemaking is predicted to increase due to climate change, which, as a result of higher temperatures, may accelerate malic acid breakdown, leading to a higher pH of juice at harvest and increasing the amount of tartaric acid added to achieve a low pH. The genes involved in acid metabolism could be used in breeding programs to increase the acid concentration of berries and raise the pH of juice counteracting this problem. It is also well-documented that tartaric acid and malic acid concentrations vary between different cultivars of grapevine, and this variation may be used to discover genes involved in acid metabolism.