Term for the conversion of malic acid in the milder tasting lactic acid (lat. malum = apple, lac = milk) used in the production of fruit juice, Wine and sparkling wine ( champagne. sparkling wine ) plays an alternative role. The process is also referred to as biological acid degradation (BSA), bacterial malic acid degradation, microbial acid degradation or apple lactic acid fermentation, as well carbon dioxide is released. But it is actually not a real one fermentation, but was previously thought to be. Around 1890, the suspect was then in Geisenheim active Dr. Hermann Müller-Thurgau (1850-1927) correctly bacteria as the cause. Dr. Wenzel Seifert (1862-1942) was then in 1903 Klosterneuburg Wine Institute identify the acid-degrading bacterium and call it "Micrococcus malolacticus". The BSA is almost always used today red wine, but basically in front of you Barrique, applied. The advantages are reduction of malic acid, more fullness through the lactic acid, less need for sulfur dioxide and better microbiological stability.
Especially White wines can be a typically buttery-creamy malolactic note exhibit. If the BSA does not work properly, serious wine defects are also such as bitter. vinegar sting. Geranienton. Lindton. Mannitstich or Lactic acid sting (Yoghurt / sauerkrautton) possible. There may also be a loss of color in weak red wines and impaired taste. The loss at fruitiness is one of the reasons why there is usually no BSA for white wine (except in Switzerland, where this is common). Although white wines also contain malic acid, in contrast to red wine this is desirable here because it makes the wine lively and refreshing. With some grape varieties such as Chardonnay, the BSA can be used for refinement, as far as the so-called buttery Sound is desired. This is also common for some producers of the chablis, The process is used for fruity wines such as. B. the Riesling or bouquet places hardly used.
It is a natural process in winemaking, which is started spontaneously from about 16 ° Celsius by existing or possibly by added bacteria (Oenococcus oeni). If no biological acid degradation is wanted, the wine has to go as quickly as possible after fermentation lees deducted, clarified and sulfurized. It can also arise spontaneously and independently (even during alcoholic fermentation), which is caused by cooling and reductive expansion can be prevented. Regulation or interruption are also possible by adding the enzyme lysozyme possible. If expressly requested, the BSA is deliberately initiated or approved after alcoholic fermentation. The start can be made by stirring from the rack, by blending with a wine that is already in the BSA process or (which is usually the case) by adding so-called starter cultures, these are special Lactic acid bacteria, respectively.
At this point, a sulphurize absolutely not because the starter cultures are very sensitive to it. The required or ideal wine temperature for this process is around 22 ° Celsius. Ideally, an acidity or PH value of at least 3.2 pH (there is no proliferation of lactic acid bacteria) and one Residual sugar content below 20 g / l. It becomes malic acid first, then the citric acid and finally the residual sugar is converted. As a rule of thumb, 2 grams of malic acid produce around 1 to 1.2 grams of lactic acid. The total acidity decreases in wine by around 1 g / l.
The biological acid degradation can take between 10 and 40 days; so this can be a relatively long process. Sometimes only a part of the wine is subjected to this process so that the acid content is not too low; then the wine is mixed. The process is very complex and must be closely monitored by measuring the malic acid content. An uncontrolled or excessive acid breakdown is considered drop in acidity To classify (wine defects). Once the BSA has ended, it is only allowed to sulfurize after one or two weeks clarify respectively. During this period, oxygen access must be prevented (full containers). In the event of improper operation, allergenic Fabrics like histamine and tyramine be formed. See also under deacidification and leavening,
Complete lists of the numerous vinification measures or cellar techniques, as well as the various types of wine, sparkling wine and distillate regulated by wine law are under the keyword winemaking contain. There is extensive wine law information under the keyword wine law,