White wine vinification: methods and consequences
The vinification of white wines is an art, requiring a great deal of attention throughout the process, from the harvesting of the grapes to the maturing of the wine. We will help you to see it more clearly thanks to this didactic guide.
A few reminders for the record. You regularly read or hear words like "yeast", "chaptalisation", "sulphur", "bâtonnage", "oxidation", "stainless steel vats", etc. when you visit a winemaker. These terms that describe the stages of wine making often give indications on the style of wine you are going to taste, its texture, its fruitiness, its taste, etc. We will therefore try to decipher some of these expressions for you, so that you can better understand their hidden meaning, especially concerning white wines today. Let's also remember that everything starts with grapes and therefore in the vineyard. And that we will start from the assumption that the grapes of our future white wines are of good quality, because if it is possible to produce bad wine from good grapes, it is impossible to make good wine from bad grapes!
Some general principles to start with. Most white wines are made from white grapes. But not only that... In fact, the vast majority of black-skinned (or rather very dark red) grapes have, like white grapes, white juice. If we press these black grapes without letting the skins macerate, we will obtain white or barely "stained" juice as we say in oenology. Everyone knows the champagnes produced from pinot noir or pinot meunier, whose colour is almost the same as those made from pure chardonnay and which are called "blancs de blancs" to indicate the grapes that produced them.
The vinification of white wines is then globally more technical than that of red wines. The most delicate aspect is the preservation of fruit, freshness and acidity, key points in the appreciation of most white wines. As soon as the grapes are picked, the risk of oxidation is very high and its consequences are much more noticeable on the taste of the future wine than in the case of red wines, which have a greater margin of tolerance. To avoid this risk, it is often preferable to harvest the whites very slightly under-ripe because a very ripe harvest weakens the skin of the grapes. This is also why, in hot regions, white grapes are sometimes harvested at night or as early as possible in the morning. The question of transporting the grapes from the vineyard to the press is also essential: the use of small containers (crates) to avoid damaging the grapes and the length of transport are essential here.
Pressing without rushing
The first choice of the winemaker is either to press the grapes that have just arrived at the winery immediately or to carry out a short cold skin maceration. In this case, the grapes are completely destemmed and then left to macerate in the cold for 12 to 48 hours, with the crushed grapes remaining in contact with the skins in order to extract a maximum of aromas. Skin maceration gives the whites a more pronounced fruity and varietal character and reinforces the aromatic contribution. The length of this maceration allows the intensity of the fruity character that the winemaker wishes to give to his wine to be determined.
The second key moment is the pressing. And in particular its progressiveness and the gentleness (slowness) with which it is carried out. Pressing that is too "violent" risks giving herbaceous tastes and above all crushing the pips, which could release bitter and vegetal flavours. Today, horizontal presses are used, and increasingly pneumatic presses (with a membrane that inflates to progressively crush the grapes) which allow a better distribution and above all a very precise dosage of pressure. But some traditional winemakers like to use old vertical presses which they think are more precise (there are still many in Champagne).
Whatever the type of press, the winemaker can carry out several successive pressings, increasing the pressure each time. Sometimes only the first pressings are used, the last pressings, of lesser quality, being downgraded to table wine or being added only very partially to the final blend after being vinified separately.
At this stage, the pressed juice is a beige/brown liquid that still contains a lot of solids. To produce a good white wine, fermentation must take place with clear juice. The winemaker will then proceed to what is called "débourbage" which consists of eliminating all the particles in suspension. This operation is most often done by gravity, by collecting the lees at the bottom of the tank, or sometimes by centrifugation, a much more violent method that is only used for wines of lesser quality.
This brings us to the stage of alcoholic fermentation. As with red wines, this fermentation can start spontaneously with the so-called "indigenous" yeasts that are naturally found on the skin of the grapes or in the cellar. Otherwise, the winemaker can choose to use "selected" yeasts, either produced from yeasts chosen once and for all and reproduced in the laboratory, or bought from laboratories. These yeasts can sometimes be used to artificially enhance the aromas, reinforcing the very "sauvignon" side of a Sancerre or exaggerating the buttery aromas of a Chardonnay. But this is no longer the world of great wines...