Winemaking - into the wineryWine Learning, Winemaking - The Facts Wine Advice Learning Learn about wine Winemaking http://www.decanter.com/wine-learning/wine-advice/winemaking/475741/winemaking-into-the-winery
On arrival at the winery the grapes will be crushed and
de-stalked. Pressing then follows to release the juice. The gentler the
pressing, the finer the juice. The juice (also called 'must') is allowed to
settle for a few hours. Any adjustments to the must can be done at this stage,
including the addition of extra sugar ('chaptalisation'). A little sulphur
dioxide, the main preservative used in winemaking, is usually added as well.
It is normal nowadays to add a yeast culture to the must to start the fermentation. The yeast attack the sugar and convert it into alcohol and carbon dioxide. Most white wines are fermented at a low temperature between 15 and 20 degrees to retain freshness. It takes about two weeks for all the sugar to be converted, leaving you with a dry white wine. Most fermentations now take place in stainless steel vats, although some of the smarter white wines are fermented in small oak barrels.
Once the fermentation has finished the yeast sinks to the bottom of the vat and forms a sediment (the 'lees'). Whilst resting on the lees wine can undergo a second transformation called 'malolactic fermentation'. In this process bacteria attack the malic acid (which has a sour, green taste) and convert it into lactic acid (which is softer and more buttery). Winemakers can now decide whether to encourage or block this transformation.
The wine will then be drained out of the vat leaving the lees behind (a process called 'racking'). Most white wines will then be matured for a short period, usually around six months or so. If this period is spent in oak barrels, the wine will pick up some of the distinctive oak flavours. By contrast, if this time is spent in stainless steel, the wine will retain its pure fruit character.
On arrival at the winery the black grapes are crushed and de-stalked, but are then pumped direct to the fermentation vats. The essence of red winemaking is that the must will ferment in contact with the skins, from which colour and tannin are extracted. Any additions of sugar, sulphur dioxide or yeast can be made directly to the fermentation vat. To assist in the extraction of colour, most red wines are fermented relatively warm(25-32 degrees). It is also usual to mix the skins and must together as much as possible during the fermentation.
Once the fermentation has finished most of the red wine can be drained off through gravity. This component is called 'free run' red wine. The skins and pips are then removed from the vat and pressed to release the 'press wine'. The latter can sometimes be excessively harsh and tannic, but on other occasions it can be blended with the free run wine to improve its body.
All red wines undergo malolactic fermentation to soften them, before racking and maturation. Red wine is usually matured longer than white - around 18 months or more. As with white wine, the use of oak barrels (particularly if they are new) will have a significant effect on the wine's character. Because the red wines spend so long in wood, it is normal to rack them every three months or so to remove any sediment that has accumulated.
Of course it is possible to make rose just by mixing red and white wine, but this is not the usual approach. The normal technique is to take black grapes, crush them, and allow the juice to stay in contact with the skins for a few hours. The juice will pick up some pink colour from the skins, and once this is achieved, the juice is drained off the skins. From then on the production of a rose follows the white wine process, with a cool fermentation and a short period of maturation.
Only sparkling wine from Champagne can be called Champagne. All other sparkling wines must be labelled as such. Various techniques exist for making sparkling wine.
The traditional method involves taking a base wine and putting it through a second fermentation in bottle. The carbon dioxide produced during the second fermentation cannot escape from the bottle and so the wine turns fizzy. The traditional method is the most expensive and time-consuming, and is used for all the great Champagnes. Other sparkling wines such as Cava (Spain) use it, and label their bottles accordingly - 'Traditional Method'.
The tank method also involves a second fermentation, but in this case it takes place in a large vat, rather than in an individual bottle (e.g. Vin Mousseux and most Sekt).
Carbonation or the bicycle pump method involves taking a base wine and injecting carbon dioxide. This is the cheapest method - also used for fizzy canned drinks. The bubbles are large and disappear quickly.
Various techniques exist for making sweet wine. If a winemaker is lucky enough to have grapes with noble rot, then these berries contain so much sugar that the yeast cannot ferment it all, leaving some residual sweetness (e.g. Sauternes). A dry wine can be sweetened by adding unfermented grape must (e.g. Liebfraumilch). Note: It is usually illegal to sweeten a wine just by adding sugar. The fermentation can be arrested either by refrigeration (e.g. Asti) or by the addition of brandy (e.g. Port).
Fortified wines tend to have complex production processes which differ markedly from each other. However, brandy (also known as 'grape spirit') is added during their production. With Sherry the spirit goes in after the fermentation, whereas with Port it goes in during the fermentation.