The yeasts, the containers that are used and specific operations characterize the final product of the fermentation of wine. These are important choices that determine the end result.
The alcoholic fermentation of wine is the chemical process by which glucose is converted into ethyl alcohol, carbon dioxide and heat. This task is performed by yeasts (unicellular fungi), added to the must in anaerobic conditions, i.e. in the absence of oxygen. One of the most widely used yeasts is Saccaromyces Cerevisiae.
The yeasts can be selected or indigenous, depending on the production style chosen by the oenologist. Furthermore, the oenologist can decide to have total or almost total control over the process and ensuing processes, or prefer a “hands off” approach, minimizing intervention. During fermentation, other substances are also produced, called secondary substances such as glycerin, acetic and succinic acid which contribute to the characterization of the aroma.
At what temperature does fermentation take place?
The fermentation process takes place at temperatures compatible with the life of the yeasts: if it is too cold or the temperature exceeds 35 degrees, fermentation does not start or stops.
Depending on the type of grape, fermentation occurs at different ranges:
- For white grapes, a temperature between 12 and 22°C must be maintained.
- For red grapes, temperatures between 20 and 32°C must be maintained, to facilitate the extraction of the colour and tannin.
During fermentation, sulphur dioxide is also often used because it has an antiseptic, antioxidant and antimicrobial action, to avoid harming the wine’s taste and colour, favouring a selection on the most suitable yeasts for this purpose.
Where does the fermentation take place?
Fermentation can take place in steel, wooden or concrete containers or amphoras, depending on the grape variety used, the wine to be obtained, and the local tradition. Steel tanks are usually more common, at a controlled temperature to stabilize the progress of the process and keep it under control.
The basic steps of alcoholic fermentation
Here are the main steps of how wine fermentation takes place based on the type of grape, and therefore on the final product that will be obtained:
- White grape variety: after the grapes arrive at the winery, soft
pressing is carried out
so as not to break the pips and obtain the free-run must. Fermentation begins,
and at the end the wine
is filtered and
clarified, and then refined in a
steel, wood or bottle container.
- Red grape variety: must is used in which the skins are left to macerate, to extract the color. Pumping must is necessary to maintain the top (the solid part brought to the top of the tank): the longer the marc is in contact with the must, the greater the extraction of the pigments and intensity. It is then necessary to decant and rack the wine, after which it can be aged in containers of different materials before being bottled.
Some interesting facts about novello wine and its fermentation
Novello wine is a type of wine that can usually be put on sale between the end of October and mid-November in the year of harvest and is sold by December 31 of the same year.
Tradition links novello wine to the feast of San Martino on November 11, a time to take stock, after a year’s work for winemakers. Novello wine is very famous in France, where it is produced from Gamay grapes in the Beaujolais area, from which it bears the name (Beajuolais Nouvea).
This wine is obtained from carbonic maceration, i.e. by placing whole bunches in a container saturated with CO2, in order to trigger intracellular fermentation in the grapes, thanks to the yeasts present.
This technique can also be used only partially (semi-carbonic maceration) when you want to obtain a wine with pronounced and juicy fruity aromas. Many Burgundy Pinot Noirs, even of excellent quality, are produced using this method in part during fermentation.