Several fruits store large amounts of organic acids in their vacuole, and these acids are
converted back to sugars during ripening, a process termed as gluconeogenesis. Several
irreversible steps in the glycolysis and citric acid cycle are bypassed during gluconeogenesis.
Malate and citrate are the major organic acids present in fruits. In fruits such as grapes,
where there is a transition from a sour to a sweet stage during ripening, organic acids
content declines. Grape contains predominantly tartaric acid along with malate, citrate,
succinate, fumarate, and several organic acid intermediates of metabolism. The content of
organic acids in berries can affect their suitability for processing. High acid content coupled
with low sugar content can result in poor quality wines. External warm growth conditions
enhance the metabolism of malic acid in grapes during ripening and could result in a high
tartarate/malate ratio, which is considered ideal for vinification