Winemaking is a highly complex process. Overlooking some little detail can significantly lower its quality and even spoil the entire production. One of the procedures that requires careful attention is malolactic fermentation. In the next section, we go deeper into this process and give you the keys to make the most of it.
What is malolactic fermentation, and what is it used for?
When we talk about malolactic fermentation, we are referring to the natural process by which certain lactic bacteria convert malic acid into lactic acid. It usually happens in autumn, as long as the temperature is not too low for lactic bacteria to grow. In these cases, MLF will not occur until the temperature rises.
What are the dangers of delaying malolactic fermentation?
Normally, once alcoholic fermentation has been completed, wines are stored without adding sulfur dioxide to allow the bacteria to grow, as bacteria are very sensitive to the presence of sulfur dioxide. The problem is the increased growth of other, less desirable microorganisms during this time, such as acetic bacteria and the highly problematic Brettanomyces.
For this reason, it is recommended that you perform microbiological counts in wines that have not undergone malolactic fermentation and have low sulfur dioxide content. These counts help ensure that there are no bugs in the wine, and if any are found, the wine should be treated with alternatives to sulfur dioxide, such as fungal chitosan.
Temperature
The bacteria involved in malolactic fermentation are activated at temperatures above 10 °C and below 25 °C, but the optimal temperature is 20–23 ºC. It is not recommended to start malolactic fermentation outside these values.
One option for performing malolactic fermentation during winter is to heat the wines to a more appropriate temperature. Tank liners or heat exchangers can be used, but they require the warehouse to have equipment to heat the water used by these systems. An alternative that does not require a large investment is the use of mobile electrical resistor systems designed for wine. To find out more about these systems, please contact Agrovin’s sales department.
Nutritional aspects
Similar to yeasts in fermentation, whose main nutrient is sugar, the main substrate for bacteria is malic acid. However, they also need a number of compounds, such as amino acids and trace elements, to optimally lead to fermentation.
After alcoholic fermentation, wines have enough of these compounds provided during the lysis of yeast. This does not happen when malolactic fermentation takes place after winter. In these cases, the wines’ natural decanting process reduces turbidity and, likewise, the nutrients necessary for MLF. Using nutrients specific to lactic bacteria may therefore be beneficial.
Other factors
As with malolactic fermentation in autumn, there are other factors that influence the MLF in spring, such as pH, alcohol level, and, as mentioned above, sulfur dioxide.
Tips for optimizing the fermentation process
Making good wine depends a lot on controlling the natural processes involved in winemaking. If data is regularly collected and defects are corrected, it is possible to obtain good results despite any obstacles that may arise. Here are some tips to ensure optimal malolactic fermentation:
- Temperature. Keep the temperature between 20 and 23 ºC. If it is cold in autumn, it is best to store the wine until spring and start this secondary fermentation then.
- Specific nutrients. If fermentation is carried out in the spring, it is important to reactivate them and find a favorable environment. There are nutrients available for this, such as Actimax Oeni, which provides the amino acids and minerals that are essential for growth.
- Bacteria levels. If the population of the existing bacteria is too low, one of the starter cultures sold by Agrovin can be added.
In summary, malolactic fermentation is one of the most delicate processes in winemaking and requires careful attention to achieve optimal results. At Agrovin, we have extensive experience and highly qualified staff to help you optimize the malolactic fermentation process. Contact us, and we’ll be happy to help you.