A Guide to Malolactic Fermentation
Malolactic Fermentation, also known as Secondary Fermentation or “Malo”, is the process in which Malic Acid in the wine converts to Lactic Acid.
What is Malolactic Fermentation?
As stated above, it is the process in which Malic Acid in the wine converts to Lactic Acid. The primary role of Malolactic Fermentation is to deacidify the wine which affects the sensory aspects of wine, making the mouthfeel smoother and it adds complexity to the flavor and aroma of the wine. The deacidification of the wine happens by converting the harsh diprotic malic acid into the softer monoprotic lactic acid. Nearly all red wines go through Malo while only a few whites, like Chardonnay and Viognier, do. One way to recognize if a wine has gone through Malo is if it has a creamy, buttery mid-palate texture. The buttery flavor comes from diacetyl, a by-product of the reaction.
What is Diacetyl?
Diacetyl is a flavor metabolite produced by lactic acid bacteria known as Oenococcus Oeni. Oenococcus Oeni is the main bacteria responsible for conducting Malo, due to its ability to survive the harsh conditions of wine. It is responsible for the production of the sensory aspects noted above. Malo can happen naturally, though often inoculated with the bacteria culture to jumpstart the process.
When does Malo take place?
Malolactic Fermentation can happen in two different ways, during primary fermentation or after. Amid fermentation, it is Co-Inoculation. After fermentation, it is Post-Fermentation Inoculation. Inoculation that takes place after alcoholic fermentation is the most common practice. When you add bacteria cultures like MBR31 after fermentation is complete, it jumpstarts the Malo process. Co-inoculation takes place at the start of alcoholic fermentation, which allows winemakers to focus on other things such as the improvement of flavor development.
What are the signs that Malo is in progress, and how do I know if it is finished?
The best way to identify malo in progress is bubbles! The malolactic activity can be detected by the presence of tiny carbon-dioxide bubbles. When the bubbles stop, Malolactic Fermentation is complete. This can take anywhere between one and three months.
What are the benefits of each method?
Firstly, the benefits of post-fermentation inoculation include better control of the start time duration of Malo. Lessened biogenic amine production leaves the wine unprotected by sulfite for a limited amount of time. This allows less potential for spoilage by other organisms. It reduces the incidence of excessive volatile acidity and enhances flavor profiles and complexity. The benefits of co-inoculation include lower levels of the inhibitory alcohol that are present at the start of Malo, and no need to apply external heating to the ferment due to the heat generated by the yeast fermentation. This results in faster completion of Malo. This means the wine can have sulfite added earlier and reduces the potential for the growth of spoilage organisms. Finally, a bonus is that bacteria added at the start of the yeast fermentation encounter a nutrient-rich environment.
Need assistance with your winemaking process?
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