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Fermentation and secondary fermentation

Fermentazione e rifermentazione: il processo - EFW
Written by EFW Staff

Fermentation and secondary fermentation, are they the same process?

Fermentation with maceration

The trading allows the creation of the must in contact with the pomace, instead in the precious wines, the winemaker will remove the stalk to avoid the strong tannin taste in the wine. Now, the fermentation starts. The peels and seeds macerate with the must, the anthocyanin will be the first substances to release the colour in fact they are, in fact the components that give the red colour of the wine. The polyphenols are contained in the peel as well and are released less quickly but they have an important anti oxidant role. In the white wines, there are few quantities of polyphenols, for this reason they are really sensitive to the oxidation process. The temperature plays a fundamental role in the solubility of the polyphenols, it has to be around 25-28 °C.
At the beginning, the fermentation is called “tumultuous” because of the development of carbon dioxide; the must starts, in fact, to boil intensely. The maceration can last form 1 to 3 weeks according to the desired result.
The good course of the fermentation depends on the balance among various factors of the process: first of all the temperature has to be controlled, never beyond 37°C, instead for the white wine it is preferable a temperature below 22°C. The right concentration of the must has to be not too acid otherwise the yeast can encounter difficulties to activate the fermentation and the bacteria could prevail. Thus, in the first phase, it is necessary the oxygen to make the yeasts breath.

The yeasts and their role during the fermentation

Yeasts are single-celled microorganism, naturally living on the peels and the stalks. They begin the fermentation even if they aren’t able to survive to the alcohol and the sulphur dioxide, for this reason it is necessary to add other yeasts, called Saccharomycetes that are able to follow the fermentation in the right way.
If diseases, such as the downy mildew, affect the grapes it is necessary to select the yeasts in order to eliminate the original ones. A technique often used is the creation of the starting yeast: a part of the must is pasteurized and inoculated of selected yeasts, they grow and then add to the must.

Alcohol as the result of the fermentation

Sometimes we hear about the alcohol derived from the fermentation that was born from the action of the yeasts on the sugars. The quantity of alcohol, also called acquired alcohol is always written on the label together with the sign % as expression of the alcoholic volume. The potential alcohol, instead, is the alcohol that can be obtained from the sugar residue and it is usually written on the label of the sweet wines. The total alcohol is the sum of the acquired alcohol and the potential alcohol.
Fermentazione e rifermentazione al microscopio - EFW

Malolactic fermentation

This type of fermentation starts spontaneously in spring, when the climate is mild. The malic acid, that gives to the wine the bitter and harsh flavour, becomes lactic acid and carbon dioxide. The malolactic fermentation can be also induced: the main bacteria that help this process are the Leuconostoc and the Lactobacillus. If the wines have experienced the malolactic fermentation, they will be softer, well balanced and with little astringency.

Secondary fermentation

The secondary fermentation happens to liven the wine up and to correct some faults. It can be realized adding sugar, silent must (the must with sulphur dioxide), yeasts and fresh pomace. Treaded grapes, slightly withered are added to the still wine whereas the Charmat method foresees the addiction of yeasts and sugars to still wine in the pressure tank.
The temperature during the fermentation has to be kept between 12-18°C.
The same process is used for the production of the Asti DOCG Spumante.
Continuous reassembly allows to maintain the temperature at -4°C, the perfect temperature to safeguard the precious and characteristics aroma of the wine.
Finally, the Traditional method, which foresees the secondary fermentation in the bottle. Sugar and yeasts are added to the base wine and then bottled; after the foam starts, the residuals are removed thanks to the technique of the “remuage”; it is followed by the disgorging, then it is added the “liqueur d’expedition” and finally the corking.
Images’ source: wikimedia.org

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