Monitoring the Malolactic Fermentation
The malolactic fermentation can be monitored microscopically by looking for the presence of bacteria and taking care to know that the bacteria seen are lactic acid bacteria and not acetic acid bacteria or bacilli. The cell morphology seen can sometimes be used to determine if Lactobacillus, Oenococcus and/or Pediococcus is present. The malolactic fermentation can also be monitored by assessing changes in the levels of acid species present. Lactic acid can come from yeast metabolism or from the metabolism of sugar substrates by lactic acid bacteria so the appearance of lactic acid is not a good measurement of the progression of the malolactic fermentation. On the other hand, loss of malate can be used to follow the malolactic conversion. Malate levels can be monitored in several ways using techniques such as HPLC or capillary electrophoresis, or by using an enzymatic assay. The simplest method for monitoring malate levels is to use paper chromatography. This can easily be accomplished in any laboratory setting and does not require highly specialized equipment. However paper chromatography is a qualitative not a quantitative assessment.