Conducting a successful malolactic fermentation

Wine production criteria for ensuring success in malolactic fermentation.

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Parameter Recommendation Action


Fruit condition

Between 3.20 and 3.50

Visible rot, off odors

Acid addition after cold soak


Crush/Destem Maceration


Potential alcohol

<40 mg/L total for white

<70 mg/L total for red


Minimize SO2 by using sound grapes

Harvest parameters

Alcoholic Fermentation Yeast strain Use yeast strain that is compatible with ML bacteria Check with yeast supplier
Malolactic Fermentation Inoculation strategy: Timing, Strain

Inoculate with starter culture

Post-alcoholic fermentation

Consider strains recommended for certain difficult wine conditions

Direct, Step 1, or Build up: follow manufacturer recommendation

Strains available with low pH tolerance, high SO2 tolerance and high alcohol tolerance

Malolactic Fermentation Temperature 64-71°F (18-22°C) Inoculate while wine still warm from primary ferment Temp-controlled cellar/tanks
Malolactic Fermentation SO2 < 5 mg/L free NO SO2 additions until MLF complete
Malolactic Fermentation Alcohol < 13.5%

Consider higher alcohol tolerant ML strain

Use acclimatization steps for culture prior to inoculation

Malolactic Fermentation pH 3.20 to 3.50 Acid adjustment if necessary (not recommended during MLF) Be alert to microbial spoilage issues if you have a high pH
Malolactic Fermentation Nutrients

Consider ML nutrients if vineyard lots have been problematic in the past or you used high nutrient demand yeast strain

Conduct MLF on yeast lees

Follow manufacturer recommendation

Keep wine on light lees during MLF

Malolactic Fermentation MLF progress

Regular monitoring

Microscopic examination for Lactobacillus, Pediococcus

Monitor VA as indicator for spoilage bacteria PCR analysis

Paper chromatography, enzymatic analysis, external lab analysis

If presence of spoilage bacteria consider lysozyme and re-inoculation after 2-3 weeks

Post Fermentation & Aging MLF completion Malic acid < 30-50 mg/L Confirm with enzymatic assay or external lab analysis before making SO2 addition

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