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Wine is surely one of life's greatest pleasures!
Wine rejoices the heart of man and joy is the mother of all virtues.
Johann Wolfgang von Goethe - German philosopher
Wine is a fascinating subject, incorporating elements of science, geography and human skill and most importantly, passion. Winedeal has outlined here the winemaking (vinification) processes. If you wish to learn more specific information, please click on the separate Red wine, White wine and Champagne sections.
Vinification
The winemaking process really starts at the harvest, or the picking of the grapes. In the Southern Hemisphere, this process starts earlier in the calendar year (ususally at the beginning of April) than in the Northern hemisphere (September time).
After the harvest and checking the sugar levels of the grapes, they arrive at the winery, where they are checked for their potential degree of alcohol. At this stage, the grapes pass along a conveyor belt to remove unripe or diseased grapes, and any other "foreign" material, such as leaves.
At this point, the grapes are destemmed and crushed, which breaks the skins of the grapes and allows the juice to run out. The grapes are then pressed, usually using a pneumatic press and the juice that follows will undergo fermentation. It is possible to do a pre-fermentation maceration to obtain more tannins, but the winemaker must be careful not to extract too many tannins, which could give the wine an unpleasant bitterness.
At this stage, sulfur dioxide (SO2) is used in the winery and acts as an antiseptic and anti-oxidant. This minimises the risk of off-flavours in the wine. Now, the fermentation process can start and then it's a question of time of how long it takes for the yeast to convert the sugars into alcohol.
Fermentation
Yeasts are naturally present on the skins of the grapes and around the winery, so once the grapes are crushed, fermentation will start naturally. However, in New World wineries it is almost the automatic practice for the winemaker to select cultivated yeasts that are the best adapted for the wine that is to be made. This is becoming more common in the Old World too.
Fermentation is the conversion of sugar, by the interaction of yeasts, into alcohol, with carbon dioxide gas and heat as by-products. Yeasts will die when there is about 15% alcohol in the wine, even if unfermented sugar remains. Alternatively, a winemaker may choose to stop fermentation before total conversion of the sugar to produce a medium or sweet wine. The fermentation can also stop if the temperature becomes too high or too low, or if the yeast runs out of essential nutrients. Generally speaking, the fermentation process lasts 2-3 weeks, however this is totally dependent on where you are and what type of wine is desired by the winemaker. In some southern regions, the fermentation will last only a few days to produce as fruity a wine as possible.
After the fermentation process, the vinification processes for red and white wine greatly alter. Please refer to the specific sections to learn more about how these wines are produced.
Maturation
Most of the wine that is produced in the world is made for early, if not immediate, consumption. In this case, maturation is not required. Some quality wines have a minimum ageing period included in the laws that control their production.
There are a number of different vessels which can be used for maturation, all of which have specific effects on the wine. These include small new oak barrels, second-hand oak barrels (1-2 years old), large old casks and vats, and stainless steels vats.
After the wine's maturation but before it is bottled, the wine must be filtered. There are different ways this can be done, namely fining, chemical or microbiological stabilisation and filtration.
Fining stimulates tiny, problematic molecules found in the wine to coagulate into larger lumps which either sink to the bottoom of the wine or can be removed by filtration using egg white, bentonite or isinglass.
If the winemaker wants to prevent deposits forming in the wine, then the wine must be stabilised.
Before bottling, the winemakers do their utmost to ensure that the wine is perfectly bright. These days, with modern technology, even the finest invisible matter can be removed from the wine. However, the filters are not selective and therefore some of the character of the wine can be removed with the particles. The finer the quality of the wine, the more gentle the filtration should be (so much so that some winemakers proudly proclaim their wines are unfiltered).
Bottling
White wines are generally bottled much younger than red wines and up until the bottling, some white wines are produced for early/immediate consumption, and these will have spent their life in temperature-controlled stainless steel vats.
There is also the ongoing debate of the best closure for a bottle of wine. Traditionally, cork has been the preferred method of closure, however 5% of all bottles produced will suffer from cork taint. Cork producers have, however, invested considerable sums in developing treatments that will eradicate these problems.
Aritificial corks, usually made out of plastic, give acceptable results for wines that are not to be aged. The seal is not tight enough and so ageing is not advised because the plastic cork will offer insufficient protection against oxygen.
The screw-cap is quickly becoming the preferred alternative. Screw caps prevent the wine faults of oxidation and of cork taint, and are easier to open. There are, however, concerns about long-term ageing, however these are yet to be proved. Some argue that the slow ingress of oxygen with a cork closure plays a vital role in the ageing a wine, while others argue that this amount is almost zero in a sound cork and that any admitted oxygen is harmful. Even though most wine is consumed within a year of production, it may be advantageous to use screwcaps due to the relatively high incidence of cork taint.
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