Time that grape must spends on skins and solids during maceration. For red wines, ranges from several days to several weeks. Rosé wines spend a day or two on the skins. White wines do not normally spend time on the skins, although some winemakers will allow limited skin contact. *
To produce wine is a fairly simple thing: toss together some fruit juice and some yeast and wait. Grapes are a very good way to start because their juice contains all the right ingredients, and their skins even have a layer of ready-to-use yeast. OK, that gets us wine, but how do you create a quality wine, a distinctive wine, a wine for the ages?
A cluster of grapes consists of stems, pulp, juice, skins, and seeds. White wines are made from just the juice. But red wines need more stuff than pulp and juice alone can deliver. Red wines need, first of all, colour, and that comes from the skins. Red wines also need tannin, and that too comes from the skins (some tannin also comes from the stems and seeds). So, to make a suitable red wine, we need to leave the juice – the must – in contact with the skins. And since nothing is simple when it comes to wine (itself a simple beverage) the decisions surrounding skin contact are many.
A white wine may have some skin contact, usually measured in hours. This can give the wine a subtle boost in terms of colour and aromatics. Too much skin contact, though, can extract skin tannin and that’s something we don’t want in a white wine, so the winemaker will press the juice immediately or after brief skin contact.
Red wines can macerate in contact with the skins for hours, days and even weeks, depending on the goals of the winemaker. One way to produce rosé wines, for example, is to allow a day or so of skin contact. Sometimes enough colour can be extracted simply by pressing the grapes very slowly for hours of controlled skin contact for a wee bit of colour and not much tannin.
Now let’s follow a batch of red wine. When we say skins we’re also talking about stems and seeds … it’s a package deal. We can use a mechanical destemmer to remove as much wood as possible, but most winemakers will leave in some of the stems. Stem tannin can improve a wine’s structure, and will also enhance its ageing ability. Seeds will quickly drop to the bottom of the fermentation tank where they don’t have much effect. The rest of the mass – the skin, stems and remaining pulp – has to be controlled. Fermentation produces a lot of carbon dioxide that rises to the surface, carrying the mass of stems and skins – the ‘cap’ – with it. To keep the wine in contact with the skins, and to prevent decay setting in, the cap must be pushed back down, up to several times a day.
The winemaker will assess the wine’s progress daily, and eventually gives the order to ‘rack’ the wine off of the skins. That order can come after a few days, when a lighter, less tannic wine is the objective, or maceration can continue. After about 10 days, most of the goodness has been extracted, and this is when most wines will be racked. Some winemakers will allow the process to continue well past that mark. Wine can stay on the skins for as long as a month. An interesting thing happens in that case. Instead of extracting more and more tannin from the skins and stems, the tannins can, in fact, soften. But this is ‘white knuckle’ winemaking, and is usually attempted only by the most intrepid winemakers.