MLF in practice

Alcoholic fermentation (AF) has been extensively studied and is now well understood. Malolactic fermentation (MLF), by contrast, still suffers from underestimation and misunderstanding, especially regarding its impact on wine aroma, microbial stability, and long-term quality.
Some winemakers still rely on spontaneous MLF, but this approach can pose serious risks and lead to delays or unwanted deviations.

Today, the use of selected cultures offers much more control, safety, and consistency. 

What is malolactic fermentation?

Malolactic fermentation (MLF), also called “malo”, is the conversion of malic acid to lactic acid by lactic acid bacteria (LAB), notably Oenococcus oeni. This results in reduced acidity, improved microbial stability, and a shift in the wine’s aromatic and structural profile.

Several LAB species may be involved, but Oenococcus oeni is the only one recognised for controlled inoculation. Strains vary widely in their tolerance to pH, alcohol, SO₂, temperature, and nutrient requirements.

Why use a commercial starter culture?

While MLF can occur spontaneously, it is often slow, unpredictable, and microbiologically risky.
Using selected bacteria strains offers key benefits:

  • Control over timing and conditions
  • Faster MLF completion
  • Reduced risk of off-flavours and biogenic amines
  • Targeted impact on wine profile
  • Compatibility with selected yeast strains
  • Better management of Brettanomyces risk 

How to choose your MLF strategy?

There are two main approaches:

Co-inoculation

Bacteria are added at yeast inoculation or a few days later. This shortens the winemaking timeline and promotes fresh, expressive profiles.

Sequential inoculation

Bacteria are added after AF, making this approach ideal for wines with specific structure, ageing potential, or technical constraints.

Whether the bacteria present result in the onset of MLF is dependent on the initial bacteria concentration; at least 1 x 106 CFU/mL is required. Concomitantly, the growth and survival of the bacteria are dependent on various other factors. 

  • pH 
  • alcohol concentration 
  • total SO2 concentration 
  • available nutrients 
  • temperature 
  • yeast strain used for AF 
  • oxygen 
  • CO2 
  • organic acids 
  • phenolic compounds 
  • presence of other competing bacteria 

Spotlight on Maxaferm® ML Force

Maxaferm ML Force is a next-generation nutrient for Oenococcus oeni developed specifically to support sequential MLF.
Its unique composition, rich in peptides, vitamins, and minerals, enhances bacterial survival and reduces fermentation time, even in difficult conditions (low pH, high alcohol, nutrient-depleted musts).

  • Add just before seeding with bacteria
  • Especially recommended with Solo or Maloferm strains
  • Increases reliability in challenging wines 

How to seed with culture bacteria? 

All Oenobrands bacterial products are designed for direct addition. Simply rehydrate the freeze-dried bacteria in clean, chlorine-free water (20x weight) for 15 minutes. Then, add it to the tank and homogenise it via gentle pumpover.

How to manage the malolactic fermentation effectively? 

Keep in mind these essential parameters:

  1. Temperature: MLF typically progresses well at temperatures between 18°C to 22°C (64°F to 72°F). Temperatures outside this range can slow down the fermentation or inhibit it altogether.
  2. pH levels: The optimal pH for MLF usually ranges from 3.3 to 3.5. A lower pH can inhibit the lactic acid bacteria (LAB) responsible for MLF, making the fermentation process more challenging.
  3. SO₂ levels: Sulfur dioxide (SO₂) levels must be carefully managed to ensure they do not inhibit LAB. Typically, the total SO₂ concentration should be kept < 50 mg/L before initiating MLF to prevent any negative effects on the bacteria.
  1. Alcohol concentration: High alcohol levels can also inhibit LAB. Wines with an alcohol content above 14% can pose challenges for MLF, requiring more robust LAB strains or specific acclimatisation strategies.
  2. Nutrient availability: LAB, like yeast, requires nutrients to thrive. However, their needs are different. Use dedicated nutrients like Maxaferm ML Force for a safe, complete fermentation

Discover the ANCHOR bacteria range

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Discover the MALOFERM bacteria range

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