Reduction or conversion of the acids contained in the wine through various measures. This is particularly necessary in poor wine years when the grapes have not reached a sufficient degree of ripeness. This is generally permitted for fresh grapes, grape must, partially fermented grape must, young wine and wine. However, this depends on the wine-growing zone. For wine-growing zone A (Germany, except Baden) and wine-growing zone B (Baden and Austria), partial deacidification is permitted (but not acidification). Although a high acid content in the grape must with a low pH value results in a purer fermentation, it is advisable from 12 g/l upwards.
Grape must can also be deacidified (usually to around 9 to 10 g/l), which results in a lower flavour impact than with wine. The fact that potassium remains in the later wine results in a "rounder" acidity with a full-bodied, harmonious impression. Another advantage is that this favours malolactic fermentation, which may be carried out later. Possible disadvantages of deacidification are the risk of off-flavours and a colour change in red wine musts. In Austria, at least 4 g/l tartaric acid (total acidity) is prescribed for quality wine. There are various methods, whereby the tartaric acid content is decisive for the application:
Although the process usually referred to as malolactic fermentation is not deacidification in the strict sense of the word, it should also be mentioned. In this process, the sharper malic acid is converted into the milder lactic acid after alcoholic fermentation (usually in red wines). See also malolactic fermentation.
This is achieved by adding pure, carbonated lime (calcium carbonate) or potassium bicarbonate (potassium hydrogen carbonate). These substances form a sparingly soluble salt with the tartaric acid, which precipitates in the form of calcium tartrate. However, the malic acid is not reduced in the process. See also under contact process.
This method (also known as double salt deacidification) is used when the quantities of malic acid and tartaric acid in the wine are too high. In this case, carbonated lime is not sufficient. A special deacidification lime (calcium carbonate with added double salt crystals) is added to a portion of the wine, which precipitates both acids in the form of a double salt. These must then be removed by means of filtration and a return blend with the remaining quantity must be carried out.
This process is similar to double salt deacidification, but not only double salt but also tartaric acid is added. This results in a particularly intensive deacidification of tartaric acid and malic acid and any desired acidity level can be set. In Germany, this is known as the "Malitex process".
A high-acid wine is blended with a low-acid wine and the desired acidity is adjusted. There are corresponding procedures and formulas for this, see the section on blending crosses.
For the production of alcoholic beverages, see Champagne (sparkling wines), distillation (distillates), spirits (types), winemaking (wines and wine types) and wine law (wine law issues).
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