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How to make prosecco

This article looks at the preparation of the base wine, pressing the grapes and the fermentation process required to make prosecco.
Two goblets and a bottle of Prosecco in a vineyard
© Università degli Studi di Padova

The production of sparkling wine is made of two distinct parts: the production of a still wine (called the base wine), followed by two rounds of fermentation of this base product to obtain the final sparkling wine.

Preparation of the Base Wine

The first step of this production, the preparation of base wine, is practically white vinification, with just some little modifications.

First of all, sparkling wine needs a higher acidity than still wine, because a good level of acidity properly supports one of the main characteristics of sparkling wines–its crispness. The crispness of sparkling wines is due to the small bubbles of carbon dioxide.

Secondly, in the first fermentation, it is preferable to reach a lower ethanol content than that generally found in still wines. Why is this so? Remember that the base wine still has to undergo a second fermentation, which can increase the alcohol content by 1.4-1.5%.

Harvesting the grapes

These two objectives can be obtained simultaneously by harvesting the grapes just before they complete their maturity. This process is used particularly in the production of Champagne wines, which are, in fact, among the most acidic wines. But in the Prosecco area, the Glera grapes are also harvested before the maximum sugar accumulation, in order to preserve, in particular, the malic acid of grapes, which gives freshness to the final wine.

Pressing the Grapes

The pressing of grapes for sparkling wine production uses specific techniques to limit the contact of the juice with the skins. In fact, any excessive extraction of phenolic compounds from the skins will change the organoleptic properties of the wine by increasing its structure.

Contact must be limited to maintain the main characteristics of the sparkling wines: lightness and freshness. This, of course, will also limit the extraction of aromatic compounds from the grape skins, but fortunately (and not by chance), the grape varieties destined for this kind of production are generally not aromatic.

Champagne

In Champagne production, the techniques entail the direct pressing of entire clusters, where crushing and pressing happen at the same moment, so practically avoiding the contact of the juice with skins and seeds.

Prosecco

For Prosecco production, so extreme a procedure is not necessary—the grapes are pressed immediately after crushing, still obtaining a juice suitable for sparkling wine production.

Fermentation

After juice preparation, the yeasts are added to perform the fermentation. Different yeast strains are available to winemakers; some of them are able to produce high quantities of secondary metabolites (esters, acetates, etc.) with fruity and floral notes, while others are considered more “neutral”, influencing the wine aroma less.

Champagne

In Champagne production, after the second fermentation, the contact between the wine and the yeast cells is maintained for a number of months, so that the final aroma of the wine will be characterized by the typical yeast aroma (bread, bread crust, etc.). In this case, to favour the perception of those aromas, the use of neutral yeasts in the first fermentation is preferred.

Prosecco

On the other hand, in the case of Prosecco, in which contact with yeasts after the second fermentation is more limited and the fresh aromas are dominant, the use of “aromatic” yeasts is preferred.

At the end of the first fermentation, the base wine is stabilized and filtered, and then it is ready for the second fermentation. Since the base wine doesn’t have sugars (having sugars would make it microbiologically unstable and difficult to store for a long period of time), and instead, has ethanol to help increase its stability, it can be stored at a low temperature in wineries and used for second fermentation even after several months.

If you’d like to learn more about the making of wine, check out the full online course, from the University of Padova, below.

© Università degli Studi di Padova
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Story of a Wine: The Importance of Being Prosecco

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