Foreign wines tend to consist of just one grape variety, but in Bordeaux the wines we make are blends. This skill acquired over the centuries is expressed as simple percentages on the bottle, but it has become a very precise calculation, as Baron de Lestac will explain.
Each grape variety has specific attributes and gives the wine different aromas, tannins which can be astringent or velvety, acidity or softness, power or a certain elegance. All these characteristics have an impact on the wine's taste and even a very small amount of a particular grape can totally change a wine's profile. In the Bordeaux region, careful calculations and combinations are made based on the attributes of Merlot, Cabernet Franc, Cabernet Sauvignon and Petit Verdot for red wines, and on those of Sauvignon Blanc, Sémillon and Muscadelle for whites. The variety of grape is crucial, but so is its environment. The age of the vines is also a factor, as is the soil type where they are planted and their exposure, the way they are farmed, and above all, the weather conditions of the year in question: all have an effect on the wine's organoleptic qualities, and come into play when the blend is made. Be it Merlot's mouth-filling character or the structure of Cabernet Sauvignon, the supple nature of Cabernet Franc or the backbone of Petit Verdot, the intensity of Sauvignon Blanc or the unctuosity of Sémillon, all these factors are taken into account to create rich, well-balanced wines.
Blending is governed by strict rules instituted by the INAO (France's Institut National de l'Origine et de la Qualité), a body which can intervene at two distinct moments, according to the winegrower's choice: either when the wine is put in tank (if different wines made from different grapes are being matured together) or at a later stage, based on what is known as vinification parcellaire (making wine from individual plots). In the latter case, the producer harvests and vinifies each grape variety separately and then makes the blend before bottling. This is the preferred method as it respects the different expression that grape varieties can have when grown on different soils. It also allows the producer flexibility in terms of different ageing methods (eg. ageing in concrete tank, brand-new barrels or barrels that have been previously used).
Bringing all these elements together is by no means a simple task: it is carried out by the winemaker and the cellar master (and the owner as well, if they are involved in wine production) who taste and define the profile of each tank of the current vintage as well as those of previous years, before deciding what percentage of each to use in the blend to create the final wine. They use their experience and skills to achieve the best possible result which will become even more complex over the years.
Blending is a major feature in the Bordeaux region, as it is in the rest of south west France and Provence, due to the fact that the vineyards are larger than those in regions like Burgundy and Alsace where single varietal wines tend to be made. In the latter, a myriad of terroirs are expressed through one single grape variety, while in Bordeaux, the many facets of a single terroir are expressed through a combination of several grapes.