During the fermentation process of wine, the pH typically decreases due to the production of various acids, primarily from microbial activity. The fermentation generates carbon dioxide and ethanal, which can lead to the formation of carbonic acid when CO2 dissolves in the wine. Although carbonic acid requires H+ ions for its formation, the overall reaction dynamics contribute to an increase in acidity. Additionally, the presence of microbial waste products, which often include organic acids, can further lower the pH. Ethanal can also convert to ethanoic acid if not fully reacted with H+, although the addition of sulfur dioxide in the wine should mitigate this. The complexity of the fermentation process, including the involvement of NADH and other reactants, indicates that multiple factors contribute to the observed decrease in pH, including the production of acidic byproducts from yeast metabolism. Understanding these interactions is crucial for explaining the pH changes during fermentation.
