Chapter 7

Malolactic Fermentation in Wine

Monitoring Malolactic Fermentation

There are a number methods used to monitor malolactic fermentation which include microbiological and chemical methods. Microbiological methods include direct microscopic examination and viable culturing techniques. Chemical methods include paper chromatography, thinlayer chromatography (TLC), enzymatic analysis, and high-performance liquid chromatography (HPLC).

Microbiological Methods

Direct Microscopic Observation

The simplest way to monitor malolactic fermentation is by making direct observations of the wine through a light microscope. It is not quantitative, but when conducted by an experienced technician, gives a fast and valuable evaluation of the microflora present in the wine.

Viable Culture Plating

Contrary to direct microscopic observation, where the cells can actually be observed, viable culture plating relies on the ability of cells to reproduce, resulting in a visible colony on the surface of the nutrient media after a few days.

Chemical Methods

Paper Chromatography

Paper chromatography is a simple, affordable and reliable technique for use in the winery, and is a useful tool for tracking the malolactic fermentation status of wines(Figure 7.4). Paper chromatography is a technique used for separating the chemical compounds in liquid mixtures by utilizing their differential affinities for a stationary phase (paper) and a mobile phase (solvent).

Thin Layer Chromatography

Thin layer chromatography (TLC) is an analytical technique chemically similar to paper chromatography. It requires a different solvent and uses TLC plates rather than paper, but the remainder of the procedure is the same.

Enzymatic Analysis

Enzymatic analysis makes use of chemical analysis to determine the absolute concentration of L-lactic acid. This method uses an enzyme that specifically reacts with L-malic acid and a UV-visible spectrophotometer to monitor the progress of the analytical reaction.actor with the greatest influence on the development and fate of LAB in wine. Depending on several factors, such as the grape variety, climate, and ripeness, the minimum pH of wine before malolactic fermentation ranges from 3.2 to 3.5.

High Performance Liquid Chromatography

High performance liquid chromatography (HPLC) is a technique that offers several advantages for the analysis of compounds (including malic acid in wine), including potential for automation, high precision and it is relatively fast. However, there is a high capital cost and skilled personnel are required to operate and maintain the instrument.

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