Modification of the organic acid profile of grapes due to climate changes alters the stability of red wine phenolics during controlled oxidation

The effect of the main grape organic acids (tartaric, malic and citric) on the degradative oxidation of red wine was investigated by NMR, HPLC and spectrophotometry. Wines featuring the same pH value of 3.2 with different combinations of organic acids were prepared. Results showed that tartaric acid preserved native anthocyanins from oxidative degradation more than malic and citric acids, with malic acid being the one favoring oxidations the most and, consequently, acetaldehyde production. Wines richer in malic acids showed the highest reactivity towards saliva proteins and a potential higher astringency. Given the wide changes in tartaric/malic acid ratio with climate, these results can help to act in vineyard, as well as in winery, to manage the malic/tartaric acid ratio with the aim of improving red wine longevity.