RED WINE MAKING

PICKING - Grapes are picked when they reach an acceptable stage of ripeness. They need sufficient sugar to provide the desired amount of alcohol in the wine, they should not be too acidic, and the flavours should reach a level where the wine will display the characteristics of the style. There are a number of different units used to gauge sugar level, but probably the most useful is the Baume scale, where 1o Baume results in a 1% alcohol content in the finished wine. So the grapes would normally be picked when they are between about 12o and 14o Baume, to result in a wine with an acceptable alcohol level.

CRUSHING - After the fruit is picked it is usual practice to add sulphur (in the form of potassium metabisulphite) in small quantities to prevent oxidation of the fruit and juice, and also to slow down any bacteria and fungi (including wild yeasts). The picked fruit is then brought to the crusher where the stalks are removed and the berries broken. This releases some of the juice and enables access to the rest for the yeast. Once crushed the grapes become a mixture of juice, skins and seeds, and this is called must.

FERMENTATION - Most modern winemaking involves adding a selected, commercially prepared yeast variety to the must. It is possible to use the wild yeasts that live on the grape berries, but this can be unreliable, and result in the production of undesirable flavours. Yeast nutrients are also added to keep the yeast working in optimum conditions. If the juice is not sufficiently acidic, tartaric acid can be added at this stage as well. oC, and this will facilitate extraction of chemicals called anthocyanins from the grape skins. It is these chemicals that give red wine its colour, and the longer the juice is kept in contact with the skins (which contain the anthocyanins), the darker the colour of the wine.

PRESSING - When the wine has been fermented to dryness (no sugar left) the must is placed in a press and strained. The wine runs from the press and is collected into a separate container, and the skins and seeds are left behind in the press. (The compressed skins and seeds are called "marc".) oC, and takes 4-6 weeks.

MATURATION - When the malo-lactic fermentation is complete, the wine is pumped off the yeast and bacterial residue (called "lees") and (usually) pumped into oak barrels. At this stage more sulphur is added to help prevent oxidation of the wine and kill (or at least slow down) any undesirable microbes. The barrels are filled completely so that there are no air spaces, and sealed with a bung.

BOTTLING - When the wine has reached an acceptable stage of maturity, has become clear and is chemically stable, it is racked off into bottles and sealed. The traditional seals are made of cork, and these are fine for short to medium term storage. However, corks are somewhat unreliable, and are no good for longer term storage. Most wines these days are sealed with modern closures like screw caps, which are much more reliable and effective. At bottling, the sulphur level is adjusted to counteract any oxygen and other contamination that may occur during the process. Wine is best left to settle down in the bottle for 4-8 weeks before consumption.