Sparkling Wine Making
Champagne and Sparkling Wine Production
Sparkling wine can be produced in a number of different ways. The world’s finest sparkling wine, Champagne, is made using a technique known as the “traditional method”, also known as the “Champagne method”. Other sparkling wines made using this technique include French Crémant, Italian Franciacorta and Spanish Cava. The hugely popular Italian sparkling wine Prosecco is produced using a different technique known as the “tank method” or “Charmat method”. We will explain the traditional method in detail, and will briefly outline the tank method.
The Traditional Method
Grapes are harvested and quickly brought to the winery for pressing. Pressing is a gentle process, traditionally using a shallow vertical press called a Coquard Press, though pneumatic presses are also used. It is important that pressing is gentle, and that the grapes are not crushed, to avoid extraction of colour and tannin. In Champagne, the regional authority dictates that a strict maximum of 102 litres of juice be pressed per 160 kilogrammes of fruit. Of these 102 litres, the first 82 are known as the cuvée while the balance is known as the taille. Makers of high-quality Champagne will only use the cuvée.
The primary alcoholic fermentation normally takes place in temperature-controlled vats of stainless steel, though some producers will opt for oak barrels or vats. The primary fermentation produces the “base wine”, a bone-dry still wine of neutral flavour, high acidity and a moderate alcohol level. The base wine will usually undergo malolactic fermentation, though this is a choice on the winemaker’s part and is not mandatory. This base wine will be used to blend future Champagne, generally the following year, though in some cases it will be stored in reserve for use considerably later in the future.
Blending is crucial in Champagne, where most wine is a blend of wines from different villages, grape varieties and vintages. The vast majority of vintage Champagne is also a blend, though its constituent wines only come from one vintage. Depending on the style of wine being made and its desired characteristics, the winemaker may combine as many as 70 different base or reserve wines to make up the blend. Once the blend has been decided, the wine undergoes tartrate stabilisation.
The next step is the secondary alcoholic fermentation, which takes place in the bottle. With the blend finalised and stabilised, a mixture known as liqueur de tirage is added, and the wine is bottled. The mixture contains wine, sugar, yeast, yeast nutrients and a clarifying agent. The bottled wine is then sealed with a crown cap, like a beer cap, which contains an insert shaped like a plastic cup. The bottles are cellared horizontally at a temperature of around 10-12°C, and secondary fermentation takes place over the course of around six to eight weeks. Over this time, the wine develops flavours, its alcohol level rises, and, vitally, the carbon dioxide generated by the yeast dissolves into the liquid and gives the wine its sparkle. Significantly, this also creates a huge amount of pressure inside the bottle.
Following secondary fermentation, the dead yeast will form a sediment known as lees. Over time, the lees break down and release various chemical compounds into the wine. This naturally-occurring process is known as “yeast autolysis” and imparts various signature aromas and flavours upon the wine, notably of bread, toast and biscuit. This process may go on for months or years, depending on the winemaker’s choices. The longer the wine spends in contact with the lees, the more complex it may become.
When the winemaker wishes to separate the wine from the lees, the wine must undergo two particular processes called “riddling” and “disgorgement”.
Riddling, also known as remuage, is a delicate task that involves moving the bottle very gradually from its horizontal position to an inverted vertical position. This concentrates all the sediment into the plastic insert under the cap. This work was traditionally done by hand, taking six to eight weeks to complete, and many producers still do things this way. In modern times, various machines have been developed to assist in this process, most significantly the gyropalette.
Disgorgement involves freezing the wine, and, by extension, the sediment, in the bottle neck. This is done by submersion into a cold solution. Once the contents of the neck have been frozen, the bottle can then be stood upright and the crown cap removed. The pressure causes both the frozen wine and the plastic insert of sediment to shoot out of the bottle, leaving the wine clear. The wine is then topped up with a mixture of wine and cane sugar known as liqueur d’expédition, and the wine is sealed with a cork and secured with a wire cage. The sugar added by this mixture is known as the dosage, and here the winemaker can decide whether to make a dry Champagne, a sweet Champagne, or anything in between. Some winemakers may opt for a so-called “zero dosage”, which will lead to a bone-dry wine with incredibly high acidity, as the dosage is used to balance acidity and develop flavour.
The finished wine is then aged in bottle, to allow the liqueur d’expédition to become integrated with the wine, and in some cases for further development of flavours. Ageing may take months or years, depending on local regulations and the winemaker’s choices. Most traditional method sparkling wines are ready for drinking immediately upon release.
The Tank Method
Best known for making the Italian sparkling wine Prosecco, the tank method is another approach for producing sparkling wine. The secondary alcoholic fermentation takes place not in the bottle, but rather in large sealed tanks. The winemaker places the dry base wine into the tank alongside a mixture of sugar, yeast nutrients and clarifying agent (similar to the liqueur de tirage used in the traditional method) and seals the tank for fermentation. The sparkling wine is then separated from its sediment by filtration and is bottled under pressure.
The costs of producing sparkling wine in this way are considerably lower than for traditional method wines, and so this method is used for inexpensive wines. As the winemaking process does not involve significant contact with the lees, tank method wines lack the nuanced flavour that yeast autolysis gives traditional method wines.