The acid in the wine, together with the tannins, supports the skeleton of the wine and gives the wine the ability to age. In addition, the taste of acid can not only give people a refreshing taste, but also increase the aroma of wine, such as opening a bottle of high-quality aged vinegar, and the vinegar aroma will also drift around the house.
Of course, wine is different from vinegar, and its acidity is usually derived from tartaric acid, citric acid and malic acid. Tartaric Acid (Tartaric Acid) in wine, most of them exist in the form of tartaric acid, that is, the slag that is sometimes seen at the bottom of the red wine bottle, to say more, these slag precipitates have no effect on the quality of the wine, and can be solved by changing the bottle and pouring it into the decanter.
Citric Acid is more present in the fruits of plants, especially citrus fruits (lemons, pineapples) are more abundant, compared to the content of grapes is much less.
In this issue, we are mainly talking about malic acid (Malic Acid), which is also widely present in plant fruits and is the most important acid in wine except tartaric acid. This acidity is strong and has a sharp taste like an unripe apple. Malic acid is partially consumed during the ripening of the grapes, but it does not disappear completely.
Compared with malic acid, lactic acid is much softer, it is a natural inherent ingredient in dairy products, the acidity is moderate, with the soft taste of dairy products and good antimicrobial effects.
Wine has a special stage in the process of making wine, called Malolactic Fermentation (Malolactic Fermentation, referred to as MLF for short). As the name suggests, MLF is the process of converting malic acid from wine into lactic acid, which is accompanied by the production of carbon dioxide and flavor substances.
Why MLF?
The process of MLF generally occurs after alcoholic fermentation, which will make the wine reduce the sharp acidity, the overall structure is more balanced, and the taste becomes softer and more delicate; at the same time, the organic compound diacetyl produced in the fermentation will bring the flavor similar to popcorn, butter or cream to the wine, increasing the complexity of the wine; in addition, MLF can improve the resistance of dry wine to microbial pollution.
Which wines will be MLF?
Most red wines go through MLF to reduce acidity, while some mellow white wines also enter wooden barrels for MLF, so they will be rich and rounded; for example, some Chardonnay dry whites from cool climate regions will become soft and buttery after MLF.
Of course, there are some red and white wines that also avoid MLF to ensure the retention of primary aromas. In red wines, such as Beaujolais Nouveau, there is no MLF, and aromatic white wines such as Riesling and Gewurztraminer also avoid MLF to some extent.
How does MLF work?
The MLF is carried out immediately after the end of alcoholic fermentation, at which time artificial strains are added to the liquor and the parameters of the wine are guaranteed, such as the most suitable conditions are a pH of 3.2, a temperature of 25 °C, and an alcohol content of less than 14%. In addition, the content of oxygen, sulfur dioxide and other substances will also affect the MLF of wine, which shows that this is a very complex process.
In fact, wine making, from planting to filling and even the final preservation and drinking, each stage is a complex process, which is originally a draining thing, who makes wine the blood of Jesus. Ultimately, malic acid-lactic fermentation (MLF) is designed to be soft in taste, rich in flavor, and the word "delicious" is ever-changing.