"One not only drinks wine,
one smells it, observes it,
tastes it, sips it and
one talks about it"

King Edward VII

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Sparkling wines

These are a group of wines which have high concentrations of dissolved carbon dioxide  Opening the bottle abruptly releases bubbles  The resulting effervescence lifts the wine aromas, refreshes and "tickles the palate".
Methods of production range from direct carbonation through to the the traditional method originating in Champagne - Méthode Champenoise or Méthode Traditionnelle.

Traditionelle Method - the method of Champagne

Many grape varieties are used for sparkling wines but traditionally in ultra-cool climates, such as Champagne and the Macedon Ranges, the major varieties are Pinot Noir and Chardonnay. In Champagne, Pinot Meunier is a significant contributor to the style.  Pinot Gris is an alternative for Pinot Meunier in this style in New Zealand and Macedon Ranges.

As the fermentation is carried out in two stages, grapes are picked early for the base wine to achieve low alcohol and a distinct dry (acid) backbone. 
Pinot Noir is pressed immediately to avoid heavy colour and is known as "blanc de noir" - white of a black grape.  The juice is fermented to produce a base wine - maintaining the dry (acid) structure and with low alcohol ~11.0%. Chardonnay and Pinot Gris are also bressed rapidly to avoid extraction of tannins from the skins.  The juices are co-fermented to achieve complexity.
A secondary fermentation of the base wine is undertaken in the same bottle which the consumer receives.  The base wine is bottled with predetermined amount of sugar (often sucrose) along with cultured active yeast and aggregating bentonite - a special clay. The bottle is closed with a crown seal, mixed thoroughly and stored horizontally at around 20oC.  The yeast ferments the sugar to produce carbon dioxide and additional alcohol of approximately 1.5%.  Once the sugar is expended the yeast undergoes autolysis and adds complexity to the flavour and to the structure of the mousse or bead.  The wine is stored for long periods on the yeast lees - "sur lie" - and develops increasing complexity.  Some cuvées are kept in excess of ten years and develop superb complexities.

Before completion for the consumer, the yeast and bentonite and other sediments must be removed and the ultimate style sweetness or conversely dryness obtained. This is achieved by the process of riddling, disgorging, “dosage” and topping up, sealing and dressing.
Riddling is the movement of the yeast deposits and bentonite from the bottle wall to the neck. Bottles are slowly moved from the horizontal to an inverted vertical position over several weeks bring lees to the point of the bottle. Disgorgement of the yeast is achieved by carefully chilling bottles in this inverted position and freezing the neck at minus 29oC. The bottle is placed at 45o above horizontal, the crown seal removed allowing the frozen plug to “jettison” and the bottle uprighted immediately. Dosage enables a style modification with addition of sweetening, acid and even liqueur and then a top up with the sparkling wine and sealing with a cork. The wire muzzle or "muselet" is applied to secure the cork and the bottle “dressed” with a hood and labelled ready for the consumer.

Alternative Methods of Production

Three other methods exist for their production - each represent a different price point :

Transfer Method

Instead of riddling and disgorging, wine kept on lees in a bottle is removed to a tank underpressure, adjusted for sweetness and acid, carbonation adjusted, filtered under pressure and re-bottled to a new bottle..

Charmat Method

Here the secondary fermentation is undertaken in a tank – in the manner of a true lager production - and the sparkling wine is bottled under pressure after yeast haze is removed by filtration and/or centrifugation.  The wine has a short lees contact resulting in lesser bubble stability and inferior complexity than Méthode Champenoise than the former method.

Direct Carbonation

This is akin to the way lemonade and "fizzy" drinks are produced commercially and in hotels.  Carbon dioxide is infused directly into cold wine.  Bubbles are short lived and large.

 

Each method attracts differing price points - Traditionnelle or Champagne styles naturally attracting the highest.