There are three indigenous grape varieties generally used in cava: Macabeu, with a light lemon flavour and soft floral aroma; Xarel·lo, with fruity notes, stronger, richer aromatics and greater aging potential and Parellada, with zesty flavour and sharp acidity. Macabeu is usually the majority grape in cava blends, but high quality bottles are often predominantly Xarel·lo. Chardonnay and pinot noir, grape varieties of the Champagne region, can also be used, though the use of non-indigenous grape varieties is somewhat controversial and much more limited.
One of the key differences between cava and Prosecco and some other sparkling wines is the method of carbonisation. While Prosecco can be made by adding carbon dioxide under pressure, cava must be naturally fermented, as with Champagne; though in Catalonia it must be labelled mètode tradicional rather than méthode champenoise. This natural method, which produces finer bubbles, involves a two-stage fermentation process. The grapes are pressed into a basic cuvée which is bottled with the addition of sugar and yeast (some high-end producers first ferment the cuvée in barrels). This starts the short first fermentation process.
The wine is then stored for at least nine months to carry the name cava, but up to forty-eight months for a truly exceptional wine. They are stored slanted down, the angle becoming steeper as they are turned regularly (riddled) so the yeasts can settle in the neck of the bottle. The more traditional cava houses still riddle them by hand, but the potential for exploding bottles means that many are riddled by machine.
This sediment in the neck – called the lees – scents and flavours the wine; the longer it rests on the lees, the more complex it has the potential to become. Certain producers cap their bottles with cork during this process, instead of metal caps – a process that adds its own layer of flavour. Carbon dioxide is also dissolved into the wine by the second fermentation, creating its natural fizz. When the neck is ultimately frozen to solidify the lees for removal, it is this fizz that pushes it out, soon after the bottle is inverted and the lees begins to melt.