Vineyards & Cellar
Control of Malolactic Fermentation
Malolactic fermentation is a natural process based upon the bacteriological activity of lactic acid bacteria. These bacteria degrade malic acid into carbon dioxide and lactic acid. Besides halving the total acid value in the wine, lactic acid has, in addition, only 1/3 the strength of malic acid.
||The major acids in fresh must are Tartaric acid and Malic acid. Only after the malolactic fermentation is there a certain amount of Lactic acid present. When the malolactic fermentation is 100% completed the malic acid value tends to be zero. All LINGENFELDER red wines complete a full malolactic fermentation. In addition some of the white wines may complete either a full or partial malolactic fermentation. It is a wonderful way to produce dry wines which are not sour.
||To monitor the progress of the malolactic fermentation we first must filter a wine sample in the laboratory.
||In the past we used Paper Chromatography to monitor the malolactic fermentation. The picture on the left represents, schematically, the separation of tartaric, malic and lactic acid. A standard solution with all three acids are at either end of the chart. Wine 1 has no lactic acid, Wines 2,3 & 4 have partially completed their malolactic fermentation, and Wine 5 has completely finished it.
||Unfortunately, the Paper Chromotography method is time consuming and the results are not always easy to determine accurately.
||Therefore we have changed to the more sophisticated method of using a Spectrophotometer. This measures the progress of the malolactic fermentation by enzymatic determination. The results are very precise and we can process 20-30 samples within 2 hours. If the level of malic acid is below 0,03g/L then the fermentation is complete.
||Oliver is pipetting wine samples into the cuvettes.
||At the end, the change in the Extinktion values on the Spectrophotometer serves as a basis for the calculation of malic acid levels.