On the skin of the grape is a dull, whitish-colored film of waxy substance . This is known as the bloom.Yeast and bacteria present in the air attach themselves to the bloom. When the skin of the grape is broken, the yeasts come into contact with the sugar in the pulp and fermentation can begin.
Fermentation may be NATURAL or CONTROLLED.
In natural fermentation the wild yeasts feed on the sugar and produce up to 4% of alcohol, but often also gives a slightly unpleasant taste.
At this level of alcohol, the wild yeasts die and wine yeasts continue to work until there is no more sugar left to feed them
They are killed once the wine has reached a strength of about 15% alcohol. After some time, the wine is spoilt by the action of bacteria, usually turning the wine into vinegar.
Each type of wine may be made in a variety of styles, according to:
Color – red, white or pink (rosé). Red wine is made from black grapes, white wine is made from either black or white grapes. Rose wines are made from black grapes which are crushed and fermented with skins until there is a little color
The taste of the wine, which is called the “palate”, reveals the true nature of the wine. Take a small mouthful and swirl it around the mouth, so that it contacts all parts of the mouth. This is necessary because different parts of the mouth are sensitive to different tastes.
Sweetness – sweetness is noticeable on the tip of the tongue, a wine with no sugar is called “dry”.
Acidity – Acidity is very important in wine, as it gives the wine “balance”. Too much and the wine is tart, too little and the wine is flabby.