Malolactic fermentation

The biological conversion of the strong malic acid (lat. 'malum': 'apple') into the milder lactic acid (lat. 'lac': milk) is known as 'malolactic fermentation' (common abbreviation: 'MLF' = 'malo-lactic fermentation'; 'ML' = 'malo-lactic').

This process that occurs during wine production is also known as 'biological acid degradation' ('BSA'). It is actively promoted in many red and white wines. In the past, malolactic fermentation was also erroneously referred to as 'second fermentation'. Cellar masters note that although 'malolactic fermentation' is a common term in wine production, it is not fermentation in the true sense of the word.

In wine, 'fermentation' is the conversion of sugar to alcohol (primarily ethanol) through the metabolic activity of the added yeast, whereby carbon dioxide (CO2) is released. However, yeast is not important in 'malolactic fermentation'. Instead, it is tiny bacteria that are responsible for converting the malic acid into lactic acid. In terms of size, these bacteria are more like ants compared to elephants. The only similarity between normal and malolactic fermentation is the release of CO2 by converting the acid. However, the amount of CO2 emitted during conventional fermentation is many times higher. But let's just leave it at the common term, 'malolactic fermentation', and go into more detail:

A certain Dr Wenzel Seifert (1862-1942) from Austria first identified an acid-resistant and acid-degrading bacterium as being responsible for the breakdown of malic acid to lactic acid with the release of CO2. These 'lactic' bacteria (or Lactobacillus) are species such as Leuconostoc and Pediococcus. Similar to yeasts, different types of bacteria also influence the aromas and thus the flavour of the wine.

Malolactic fermentation or acid degradation can occur naturally as a result of bacteria transferred from the grapes (e.g. on the grape skin, on stems, leaves or even on tools and in barrels previously used for fermentation) or can also be actively encouraged by the cellar master himself.

Malolactic fermentation can already occur in the must, but also later during the winemaking process or in the bottled wine. It can also take place completely or only partially. It can also be avoided by the cellar master if he so wishes. The successful growth of these bacteria depends on the temperature and certain nutrients. The pH values in the must or wine must be neither too high nor too low. These bacteria are also very sensitive to sulphur dioxide. A high alcohol level (ethanol) in the wine can also kill the bacteria completely. They feel most at home at temperatures above 20°C. At temperatures below 15°C, on the other hand, it is too cold for malolactic fermentation. In the days before modern air conditioning in wine production, malolactic fermentation often developed spontaneously during the summer months.

Cellar masters generally 'inoculate' their wines with these bacteria after alcoholic fermentation by the yeast. The residues of the dying yeast provide nutrients for the bacteria. Many other factors also influence the success of malolactic fermentation, such as the presence of oxygen, tannin, certain types of yeast, barrel ageing and the filtering of the wines.

A cellar master can consciously decide in favour of or against malolactic fermentation in the production of a wine for several reasons. One of the main reasons in favour of malolactic fermentation is often that the type of wine used could appear atypical or too bitter to the connoisseur without the reduction of the strict malic acid. Another reason in favour of malolactic fermentation is the desired aromatic change (sometimes also aromatic refinement) in the wine, which is naturally associated with malolactic fermentation. Some wines also gain pleasant 'creamy' or 'buttery' aroma and flavour nuances through malolactic fermentation.

Another cellar master might distance himself from malolactic fermentation because his wine is deliberately composed in such a way that the natural malic acid adds a special dimension of freshness and fruitiness to the wine. Natural fruit acids also contribute to the improved ageing potential of wines.

Das eher kühle Klima der Champagne bedingt oft verhältnismäßig hohen Säuregehalt in den geernteten Reben. Dies bietet sich wiederum für die maloloktische Gärung an. Somit wird die malolaktische Gärung von vielen Häusern in der Champagne bewusst gefördert. Es gibt jedoch auch einige wenige Champagner-Häuser (wie z.B. Gosset), die auf die malolaktische Gärung streng verzichten und ihre Cuvées mit der natürlichen Apfelsäure der Reben komponieren. Dadurch werden oft aussergewöhnlich frisch und fruchtig anmutende Champagne geschaffen, welche sich nicht selten durch bemerkenswerte Lagerungsfähigkeit und zunehmender Geschmeidigkeit auszeichnen.

 

 

 

Back to the lexicon & glossary | You were here: Malolactic fermentation