Malic acid

Malic acid is an organic acid naturally present in plants, including grapes, apples and pears. Its content influences the acidity of a wine: the right dosage is therefore as crucial as it is strategic, and is modulated by various oenological techniques, including malolactic fermentation.

What is malic acid in oenology?

Also known as dicarboxylic acid, it is one of the main organic acids present in grape berries, along with tartaric acid and citric acid. Here's the formula for a malic acid molecule:

    HOOC-CH2-CHOH-COOH, or C4H6O5.
This compound contributes to the final acidity felt in the mouth when tasting wine,whether red, white or rosé. Its concentration in fruit decreases with heat, but also with ripening through cellular respiration, reaching 2 to 7 g/l in ripe grape juice, depending on the year and grape variety. This quantity, inversely proportional to that of sugars, continues to decrease during the various stages of winemaking. Determining the malic acid content in the grapes and then in the must is of great importance to winemakers: it enables them to manage the organoleptic balance, and therefore the quality of a wine.

What influence does malic acid have on the taste of a wine?

This is the acid that tickles our taste buds when we bite into a fruit that's too green. When tasting a wine, it brings greenness and freshness, but also a slightly metallic and abrupt sensation. If too much is present, it can give the impression of an unripe vintage. But malic acid's role is not only sensory and not limited to aroma or taste: it is also considered an organic preservative, known as E296. Its recognized effectiveness in combating the development of micro-organisms helps to preserve wine.

How to manage malic acid dosage in wines?

Through viticulture techniques, directly in the vineyard

Managing dicarboxylic acid levels begins in the vineyard, well before harvest. It begins by ensuring that the soil is properly fertilized and that the vines are vigorous, with a good supply of water and nutrients. It continues with regular measurement of the amount of malic acid present in the grapes, according to their maturity. This allows us to define the optimum harvest date , adapted to the grape variety, the winemaking process and the organoleptic characteristics of the wine produced.

Malolactic fermentation during vinification

Various oenological techniques are also used to modulate must acidity. To reduce acidity, the winemaker can resort to malolactic fermentation, also known as “second fermentation”. Malolactic fermentation takes place after the alcoholic fermentation of grape sugars. Through the action of lactic acid bacteria, the strong malic acid is transformed into weaker lactic acide. This process adds suppleness and roundness to wines, particularly red varieties, which are more tannic.

Acidification of musts or finished wines

If, on the other hand, the aim is to compensate for an initial lack of acidity, it may be possible to use acidifying yeasts, known as “demalicants”, during alcoholic fermentation. The blending of several grape varieties can also be used by the winemaker as an acidification technique. As for addition of E296 malic acid, regulated by wine-growing region, it is sometimes used for white and rosé wines. It is added to the must in vats or directly to the finished wine.