Technical Yearbook 2023

JULY

The influence of climate change on the potassium, pH and total acidity of wines By Charl Theron Over recent decades, the alcohol concentration of wines has increased due to the higher sugar concentration of grapes when harvested. This also led to an increase in pH and a decrease in the total acid concentrations of wines. Tartaric and malic acids are the two major fixed acids in grape berries, with tartaric acid being the strongest. Tartaric acid increases during the early stages of berry growth but decreases after further development, especially after véraison. Tartaric acid, like malic acid, is not usually used in respiration metabolism, whose concentration decreases with increasing metabolic respiration. Rising temperatures increase respiration. The decreasing concentration of both acids leads to unfavourable acid sugar and acid-aroma balances. This trend can be caused by climate warming.

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TECHNICAL YEARBOOK 2023