Sparkling wine production
In popular parlance and also in the title of this article the term sparkling is used for all wines that produce bubbles at the surface after opening.
The following terms are increasingly used to designate different bottle pressures:[2] Fermentation of sugar into alcohol during winemaking always means that carbon dioxide is released.
The dead yeast cells form a precipitate called lees, that often help with appealing aromas to the sparkling wine but look unappetizing.
[6] In many cases the wine is stored on the lees – sur lie – under carbon dioxide pressure for a long time before disgorging takes place, to get a more mature character.
Col Fondo is a variant on the pét-nat intermission method, however producers are increasingly dropping the word from their labels as the name was trademarked in 2002 by two local wineries (as the spelling Colfondo).
Since French wine label regulations ban the word naturel, the appellation from Montlouis-sur-Loire is instead called pétillant originel.
Within the overall umbrella category of pét-nat there are two general approaches employed by winemakers, the choice of which is often determined by location and weather conditions during harvest as well as the scale of production and resources on hand in the winery when it comes to bottling.
The wine goes into bottle, sealed under a crown cap, where the still viable yeast, nutrient and sugar allow the primary fermentation to continue and produce the carbon dioxide that forms the bubbles.
The second method is called "entr'acte" (intermission) whereby the primary fermentation is completed to dryness, allowing the wine to be naturally cold stabilised and settled, either in an underground cellar or temperature controlled tank.
The advantages of the entr'acte method is that the wine does not need to be disgorged, there is more control over final sediment and pressure levels leading to an avoidance of gushing.
The entr'acte method is often favoured in warmer climates where faster ferments are more difficult to control, as well as where producers want to be more precise with final turbidity and pressure levels as well as minimising overall risk.
Alternatively, using a method faithful to the origins of ancestral winemaking, the wine is cold-settled before the end of primary fermentation to mimic the natural changing seasons before being bottled and then allowed to warm up again, as it would in the Spring.
Common faults are those often associated with low / no sulphur winemaking such as mousiness or excessive levels of brettanomyces or volatile acidity.
Due to the fermentation being completed in the bottle, pét-nats can often display funky characteristics, not dissimilar to still natural wines, and which represent a stylistic cross-over with traditional styles of sour beer such as lambics and gueuze.
The method's main challenge is that the production process is difficult to control and therefore requires great skill by the winemaker.
High-quality wines produced with the ancestral method, often by small growers using organic farming principles, can be complex and very distinctive.
The dioise method is used in among others the Drôme valley in France, as well as for Asti Spumante produced in Canelli in the Piedmont region in Italy.
When the sugar is converted into alcohol and carbon dioxide, the yeast is filtered and removed, and the wine containing the dissolved CO2 is transferred from the closed reactor vessel into bottles.
[18] This production method is widely used in the U.S., in Italy, especially in the Asti province, and in Prosecco wines, and in Germany to produce variants of Sekt such as Henkell Trocken.
The secondary fermentation takes place in steel tanks with special rings, or with added oak chips.
Some that were present in early production methods include yeux de crapauds (toad's eyes) which was a condition of big, viscous bubbles that resulted from the wine spending too much time in wooden casks.
