Bubbles - Champagne and Sparkling wines

Sparkling wine is a wine with significant levels of carbon dioxide in it making it fizzy. Broadly speaking, it can be divided into two main categories; some are intended to taste like fizzy versions of a still wine, others, in addition to flavours of the base wine, add complexities arising from ageing and the breakdown products of the yeasts (that add the bubbles).

One of the crucial factors in the quality of every sparkling wine is how the fizz is added. It may result from natural fermentation, either in a bottle, as with the Méthode Champenoise, in a large tank designed to withstand the pressures involved, as in the Charmat process. With low quality / cheap sparkling wine, the fizz is added with a gas injection.

Sparkling wine is usually white or rosé but there are many examples of red sparkling wines (such as Italian Brachetto and Australian sparkling Shiraz). The sweetness of sparkling wine can range from very dry "brut" styles to sweeter "doux" varieties.

CHARMAT PROCESS

(aka Metodo Martinotti; the Tank Method)
It was invented in the 19th century by Federico Martinotti, an Italian oenologist from Asti. In this method, part of the fermentation takes place in a sealed tank, which prevents any carbon dioxide gas from escaping. This carbon dioxide dissolves in the wine, and in order to ratain it, the wine must be bottled under pressure. When the bottle is opened, the dissolved carbon dioxide causes the wine to bubble.

This results in a much cheaper manufacturing process and it allows large-scale productions of the fizzy wine. This method is ideal for fresh, fruity styles of sparkling wine such as Prosecco.

TRADITIONAL METHOD

(aka Méthode Champenoise; Bottle Fermented)
Much more labour intensive than the tank method, and production costs are much higher. However, they have two main advantages in terms of quality. Firstly, through the extended contact the wine has with the dead yeast, the wines can gain complex bready, biscuity flavours that do not appear in other wines. Secondly, the bubbles are much smaller, less aggressive and longer-lasting.

Having made a high quality, dry white wine, it is then placed into special heavyweight bottles and a fresh does of yeast and sugar is added. The bottles are then capped and stored for anything from 9 months to several years. Champagne, Cava and many other old world traditional sparkling wine appellations have minimum "sur-lie" ageing requirements.

A second fermentation takes place, in which the wine increases slightly in alcohol, and the carbon dioxide, which cannot escape from the sealed bottle, becomes dissolved in the wine. During this time, amino acids and other compounds in the dead yeast cells are released and break down. This process is called autolysis and adds complexity to the wines.

The problem with this technique is the deposit of dead yeast cells that collects in the bottle. In still wines these would simply be filtered out, but since that would also remove the bubbles, another method had to be found. This process is known as remuage: each bottle has its position gradually adjusted so that over the course of a few weeks the bottle goes from horizontal to upside-down. This will move the sediment toward the neck of the bottle.

Remuage

The next stage is to disgorge (remove) the yeasty deposit, otherwise it makes the wine hazy. The plug of yeast in the neck is then frozen, and pops out when the bottle is unsealed. The bottles are topped up with a dosage of reserved wine, sweetened according to the desired style of wine. The bottles are corked, wired and prepared for release. Though the wines usually rest an additional six (or more) months so that the dosage is fully integrated before being sold.

Sources:
Wikipedia
wine-pages
VinoInLove
theKitchn
- Image by Wally Gobetz

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