Fermentation in Winemaking

By definition, “Fermentation is a catabolic process of incomplete oxidation, which does not require oxigen, and the final product is an organic compound”

fermentacion

Fermentation is an essential process in the winemaking process that must be carried out to convert the ‘sugars’ of the grapes to the ‘alcohol’ of the wine.

For many years the Greeks believed that this fascinating process of converting the sugars into alcohol was the work of Dionysus. During the middle ages, alchemists were responsable for carrying out these alcoholic fermentations without any technical bases, not until the 19th centry when Louis Pasteur (1822-1895) described and formalised the process.

There are many types of fermentation, but usually when in regards to winemaking we tend to only refer to two: alcoholic and malolactic fermentation.

Alcoholic Fermentation.

Alcoholic fermentation occurs between the sugars, that have been naturally created in the grape, and the yeast. The queen yeast variety is the Saccharomyces Cerevisiae, a yeast that either comes naturally from the grapes, or from yeasts selected in the laboratory. The joining of these two elements transform the sugar to alcohol, which releases other substances such as heat and C02.

It is important to know how alcoholic fermentation occurs and whether it has been carried out with native yeasts, or rather with selected yeasts that have been inoculated to control the process. A wine that undergoes fermentation with native yeasts is usually more complex and offers more characteristic flavours of the territory, although this production technique does run some risks as they can coexist with other wild yeasts which divert the fermentation process and therefore the final result. Alcoholic fermentation carried out with inoculated yeasts ensures a linear and stable fermentation, however this production method results in a wine with less territorial complexity.

Malolactic Fermentation.

This is the second type of fermentation associated with viticulture, where malic acid is converted to lactic acid and C02 by lactic acid bacteria. Malolactic fermentation is carried out to soften the acidity of the wine, to biologically stabilise it and modify the organoleptic qualities of it.

Malolactic fermentation is carried out after alcoholic fermentation and is carried out in a natural manner, usually at the beginning of spring when temperaturas are around 20-22ºC, or in the wineries facilities where temperaturas are climatized to  similar level.

The tank or deposite in which malolactic fermentation is carried out can also have a great effect on the style of wine, depending on whether it takes place in small and new deposits such as barrels, or larger, more neutral ones.

Here we have two wines that serve as an excellent example of how a different malolactic fermentation can affect the profile of the wine,

Ramírez de Ganuza Reserva. This wine undergoes malolactic fermentation in French oak barrels. This will result in more intense aromas from the mannoproteins that organoleptically provide lactic notes that result in a wine with more body. This style of wine has experienced a boom in popularity in recent years. .

Viña Tondonia Reserva. This wine undergoes a second fermentation (malolactic fermentation) in large wooden vats, where the contribution of mannoproteins is insignificant and the real different lies in the change of the Sharp acidity in the wine to something more pleasent.

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