High malic acid concentrations are being encountered for the 2017 vintage in Australia and New Zealand. (i.e. > 3 g/L, up to 4-5 g/L), and this is also accompanied with low sugar and pH/TA. In order to ensure an efficient and complete malolactic fermentation there are several aspects to consider.
Lallemand Oenology have a lot of experience with MLF. What does high malic acid mean for the ML bacteria;
- High malic acid will translate into high lactic acid concentrations, which can be inhibitory to O. oeni (3 g/L lactic acid).
- Some wine bacteria are more sensitive to lactic acid than others. In the Lallemand O. oeni range, Lalvin 31™, Lalvin VP41®, O-MEGA™ are the most suited; it is not recommended to use ALPHA™ in high malic acid wines.
- It is important to have favourable wine composition (pH > 3.2, SO2 <30 ppm) with high malic acid concentrations
In order to ensure an efficient and complete MLF, Lallemand Oenology have some suggestions to assist with your MLFs.
Wine Yeast
- Select a yeast strain that can undertake malo-ethanolic fermentation, a biochemical pathway whereby some malic acid is degraded during alcoholic fermentation. Malo-ethanolic yeast strains in the Lallemand yeast portfolio are Lalvin 71B™ and Lalvin C™ (these strains can metabolise up to 45% of malic acid during AF).
White wine
- Wines with a low pH; it is important to have < 30 ppm SO2, and aim for pH >3.1
- Co-inoculation with Lalvin 31™, Lalvin VP41®, O-MEGA™
- OptiML Blanc will help bacterial metabolism in low pH and/or low turidity conditions; it improves MLF kinetics
Red wine
- Aim to have the pH > 3.2 – this will help the bacteria have an active metabolism
- Co-inoculation with Lalvin 31™, Lalvin VP41®, O-MEGA™
- ML Prime™, use only as co-inoculation, and ensure that pH is higher than 3.4
ML Prime™ (Lactobacillus plantarum), only to be used as co-inoculation (with pH >3.4), is well suited for red vinification and will complete MLF very quickly during AF. Unlike O. oeni, ML Prime™ is lactic acid tolerant. This strain will efficiently metabolise up to 3 g/L malic acid and under favourable conditions (temp ca 24°C, moderate alcohol and pH >3.6) it can degrade up to 4 g/L malic acid.
Stuck or sluggish MLF (Red and white)
Where the MLF has slowed down or stopped, Lallemand can recommend a few strategies to get the malic acid below 0.2 g/L. For wines with < ~0.8 g/L malic acid;
- Use a higher dose of ML bacteria to get the MLF started again. Lalvin VP41® (MBR) is the strain of choice for restarting a stuck MLF.
- For difficult/challenging wine, acclimatization of the bacteria to the wine with 1-Step protocol will help the bacteria adjust to the wine conditions and be metabolically active for malic acid degradation. Additional information can be found in the Procedure – Acclimatization of MBR bacteria for the induction of MLF in difficult conditions.