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Malolactic culture assistance

In a recent issue of Craft Beer Quarterly, we told you that White Labs now offers liquid malolactic culture for the home winemaker. In this issue we will provide you with instructions and tips for malolactic fermentations.

Malolactic fermentation is the conversion of malic acid to lactic acid by bacteria from the lactic acid bacteria family. Lactic acid is less acidic than malic acid, which in turn decreases acidity and helps to soften and/or round out some of the flavors in wine.

Please note: We do not recommend the use of WLP675 with wines from kits, which contain potassium sorbate and affect the viability of malolactic bacteria.

1) General instructions:

Wait for fermentation to reach a gravity of approximately 5 Brix, basically towards the end of fermentation. Warm to room temperature and inoculate 5 to 7 gallons (20 to 25L) of must.

If one inoculates at the beginning of fermentation, the yeast and WLP675 could compete for resources, thereby causing a stuck fermentation.

To determine the completion of the MLF (malolactic fermentation), one can use paper chromatography and monitor the depletion of malic acid. The accepted value for a completed MLF is around 30ppm.

2) Inoculation of Must Volumes larger than 7 gallons or 25L

Each vial of WLP675 can inoculate up to 7 gallons or 25L. To inoculate larger volumes, we recommend inoculating with more vials. If time is not an issue, one can propagate the bacteria to larger volumes, but keep in mind that malolactic bacteria is a slow-growing, fastidious organism. Depending on the size of the propagation, it could take weeks to grow.

3) Propagation instructions

White Labs recommends allowing 7 days for tenfold growth. The best media for propagation is tomato juice, supplemented with fructose, malic acid, and nutrients such as that contained in MRS broth. Diluted apple or grape juice supplemented with malic acid is a good substitute for tomato juice. Approximately 2% of the total volume of finished wine can be added in order to acclimate the bacteria to alcoholic conditions. We recommend an incubation temperature of 86F (30C).

4) Optimal pH

The optimal pH is approximately 4.0, but WLP675 will handle a pH of 3.3 in red wines and 3.1 in white.

5) Additional Information

WLP675 has a high tolerance to low pH (3.0), low temperature environments (down to 55F or 12C), and high alcohol percentages (up to 15% alcohol by volume).

For information on any of the above information, please call 1-888-5-Yeast-5, or write the sales staff.