White Labs Wine Yeast –
Malolactic Bacteria Tips

WLP675 Malolactic Cultures
White Labs Malolactic Cultures have been gaining converts throughout the winery world. These are available in multiples of 1 liter sizes to inoculate 59 gallons for wineries, and in smaller quantities for home wine-makers.

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, towards the end of fermentation. Warm culture to room temperature and inoculate must.

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

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

2. Inoculation of Must Volumes larger than 59 gallons

To inoculate larger volumes, we recommend inoculating with a larger culture. 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 apple or grape juice (or must, if available), supplemented with fructose, malic acid, and nutrients such as that contained in MRS broth.  Approximately 2% of the total volume of media can be composed of finished wine, in order to acclimate the bacteria to alcoholic conditions. We recommend an incubation temperature of 30˚C.

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 55˚F or 12˚C), and high alcohol percentages (up to 15% alcohol by volume).