What are the principal factors influencing the development of lactic acid bacteria (LAB)?
Wine parameters such as pH, temperature, alcohol and SO₂ (Free and Total) have a negative synergistic effect, making the completion of MLF difficult when combined. Additionally, vineyard sprays, initial malic acid content, yeast strain used for alcoholic fermentation and wine polyphenol content can be stress factors. Challenging MLF can happen with pH <3.4, alcohol >14.5%, wine temperature <65°F or >80°F, total SO₂ >30 mg/L and/or free SO₂ >10 mg/L.

Does LAB strain choice really matter?
Choosing the appropriate LAB strain for MLF is important for both wine quality and style. An inoculation with aselected Oenococcus oeni strain reduces the potential for spoilage by other microbes by ensuring rapid onset of MLF. LAB also contribute to aromatic and mouthfeel changes through MLF. This means the choice of the appropriate strain gives the winemaker better control over aromatic and mouthfeel characteristics. Enartis offers a selection of Oenococcus oeni strains adapted to different wine styles and conditions:

• Enartis ML Silver: Due to its resistance to alcohol, SO₂ and high phenolic content, Enartis ML Silver ensures a fast and complete MLF even under difficult conditions.
• Enartis ML UNO reduces the risk of spontaneous fermentations thereby contributing to the production of wines with better sensory attributes.
• Enartis ML MCWhas been selected for its ability to produce creamy, “buttery” wines. Tolerance to low temperatures, low pH and high alcohol levels make Enartis MCW suitable for MLF under difficult conditions. 

What nutrients do ML bacteria need?
Once alcoholic fermentation is complete, yeast usually leave a wine deficient in vitamins, amino acids, minerals and other necessary nutrients for ML bacteria. To increase the resistance and survival rate of LAB in hostile environments, Enartis offers Nutriferm Osmobacti and Nutriferm ML, nutrients specifically designed for the needs of ML bacteria. 

What about oxygen and LAB?
Molecular oxygen stimulates the growth of some LAB, behaving as a growth factor. However, if too much oxygen is applied, acetic acid may be produced.

What about the production of diacetyl?
Produced by LAB, this compound is characterized by buttery notes. Diacetyl is formed from pyruvate, which comes from acid and sugar catabolism. The entire winemaking process impacts the production of diacetyl: a slower MLF speed (with low inoculation rate and/or low temperature) and slightly oxidative environment will increase diacetyl production, while yeast lees contact will break down diacetyl and SO₂ can bind with diacetyl, thus reducing its content in wine. 

To increase the production of diacetyl in wine:

• Use Enartis ML MCW
• Promote slow MLF speed with low inoculation rate and low temperature
• Reduce lees contact with racking
• Use Enartis Stab Micro or SO₂ when MLF completes and desired diacetyl levels are reached: living yeast and bacteria can break down diacetyl in an irreversible way
• Promote slight oxidative environment with lees stirring or MOX
• Limit SO₂ use as molecular SO₂ can bind with diacetyl (this is a reversible reaction). 

To minimize diacetyl production during MLF:

• Use Enartis ML Silver, a fast fermenter with low ability to produce diacetyl
• Increase fermentation speed with higher inoculation rate, higher nutrient supplementation and higher temperature
• Increase lees contact by limiting racking, co-inoculation or early inoculation: living yeast and bacteria can break down diacetyl in an irreversible way
• Protect wine from oxygen for a reductive environment
• Use antimicrobial such as SO₂ or Enartis Stab Micro to eliminate ML bacteria as soon as MLF is complete 

For more information, please contact us at (707) 838-6312.