The harvest is finished, all the wines completed their alcoholic fermentation and were pressed, and now are all safely in their barrels. It seems to be a quiet time at the winery, however, our wines are very active…they are going through MALO LACTIC FERMENTATION, or “MLF”, or “malo” in winery terms.
What is a malolactic fermentation and how does it affect a wine?
MLF normally occurs after the primary fermentation has been completed, when the grape sugars have been converted by yeast into alcohol and carbon dioxide (CO2). Lactic acid bacteria, Oenococcus oeni, (and some other species of Lactobacillus and Pediococcus) are responsible for this conversion. The major function of these bacteria is to convert one of the main wine acids,(there are two main acids and many minor ones found in grapes),L-malic acid, to another type – L-lactic acid. During this conversionCO2 is produced, so that’s why it’s called “fermentation”!
Most red wines that undergo a malolactic fermentation are improved by it, however wines that rely on a higher acidity level to show their full potential, such as most Argentine whites, would never benefit from it. Torrontés, Sauvignon Blancs, or similar younger varietals need the crispness in the acidity and youthful freshness to come through.
Lactic acid bacterial growth is inhibited by cooler temperatures, as well as the addition of sulfur dioxide (SO2) – an anti-bacterial agent. Winemakers are able to stop the onset of MLF, and can therefore control the style of wine being made by maintaining SO2 levels and lowering the wine temperature throughout the entire winemaking process.
The wines that benefit from MLF tend to be fuller-bodied, dry whites, such as Chardonnay, and most medium- to full-bodied reds. It is these heavier wines that need to be somewhat softened to ensure an attractive lower acid to fruit balance.
In our winery, Pablo Martorell, our winemaker, decided to have a partial malo-lactic fermentation in our Chardonnays and a non-malolactic fermentation in our Torrontes and Sauvignon Blancs. For our reds, however, all wines are undergoing this secondary, but very important, fermentation. And here is an interesting fact about MLF – in Argentina one of the most important lactic bacteria – the Oenococcus oeni – is in very high concentration (98%), and it is not necessary to inoculate to make MLF start, our wines start this fermentation spontaneously!
Putting a wine through a malo, when in tank or barrel, is encouraged during the winemaking process as it will be less likely to repeat the process when it is in the bottle. If a wine unintentionally undergoes MLF when in bottle, it can be disastrous to the consumer. Apart from the wine losing its fruit integrity, it will appear to still be fermenting, as CO2 will be produced and an unpleasant lactic aroma would be detected.
How does Malolactic fermentation affect taste?
Considering that MLF enhances the body and flavor of the wine, it produced wines with greater palate softness and roundness. Most winemakers believe that there is much better integration of fruit and oak if MLF occurs while the wine is in barrel. This fuller mouthfeel is, for most people, more pleasing to the palate.
It has been noted that malic acid resembles the taste of green apples, (malic comes from the Latin word for apple, malum). An appley taste is often found in wine descriptions. In contrast, lactic acid is prominent in milk and is much more rich in taste, more like full-fat butter (lactic is derived from the Latin word for milk, lac).
The mouthfeel of malic acid can be described as “hard and metallic” against the “softness” of the lactic acid. MLF is a natural de-acidification and softening of the wine’s palate.
MLF is a natural way of softening wine and making it much more acceptable to the palate and easier to drink!
Article Source: http://EzineArticles.com/4730535
