Also known as malic acid or hydroxy succinic acid, malic acid is one of the three most important organic acids in wine alongside tartaric acid and citric acid. In nature, it is mainly found in unripe apples, barberry berries, quinces, gooseberries, rowan berries and grapes. It got its name because it was first isolated from apple juice and described in 1785. In the still unripe grapes it has a high content of up to 20 g/l, in the wine it is between 0.5 and 6 g/l. Parallel to the storage of sugar during berry ripening, the reduction of must acids takes place.
Malic acid is consumed at between 20 and 30 °C, i.e. it is burned and converted into sugar during cell metabolism, whereas tartaric acid is only broken down at higher temperatures. This is why the remaining tartaric acid content in ripe grapes is always higher. Tartaric acid is considered to be a soft, pleasant acid, whereas malic acid is considered to be a more aggressive tasting acid, which makes the wine taste angular and hard.