Labo VinThe malolactic fermentation
This fermentation occurs later than the alcoholic fermentation. It is due to special lactic bacteria that transform malic acid into lactic acid and CO2. This reaction, which deacidifies the wine (lactic acid is 2 times less acid than malic acid) is often desirable in acidic red wines. While the wish of certain tartness in white wines let avoid it. Everything depends on the kind of wine you want and the starting acidity. Anyway the malolactic fermentation requires the presence of malic acid, whose ratio varies according to the starting fruit.
The malolactic fermentation can be avoided by adding metaK [ Solution 0.25 M of potassium metabisulfite (K2S2O5, Mr=222), prepared by dissolving in water 55.5 g potassium metabisulfite (failing which, 47.5 g sodium metabisulfite - Na2S2O5, Mr=190) for 1 L solution.
10 mL of this solution equals 320 mg SO2 (5 millimoles).
This solution can be kept for a long time in a tightly sealed bottle. ] to the wine. Take heed of this fermentation to calculate the final acidity. This formula can help.
Must acidity=wine acidity+1+(% malic acid/20).
Wine acidity=must acidity-1-(% malic acid/20).