Wine is made from the fruit of the grape vine. The main factors that determine how a wine will taste  are: the grape variety used; the environment in which it is grown (climate and weather, soil and slope); the care with which the grapes are grown and harvested; how the wine is made; how the wine is made; and how it is matured (including bottle-age). Many of the factors that affect quality have a cost effect and will influence the final selling price of a bottle of wine.

 

  • The most important part of the process of winemaking is fermentation. When yeasts feed on sugars in the grape juice, they produce alcohol, carbon dioxide and heat, changing the flavours of the grape juice into those of wine. 

 

  • For WHITE WINES, the grapes are usually crushed to break the skins before they are pressed to separate out the juice. Yeast is added but some winemakers choose not to use commercial yeasts, believing that the “natural” ones that dwell in the vineyard and winery give more interesting results.

 

  • The wine must is transferred to a fermentation vessel (usually a stainless steel tank, but some winemakers use oak barrels or open-topped concrete or wooden fermenters). White wines are then fermented at low temperatures (typically 12ºC - 22ºC) to preserve delicate fruit aromas. This takes between two and four weeks. Sweetness in white wines is usually caused by unfermented sugar.

 

  • Maturation is the next step and can take place in barrels or large neutral wooden or stainless steel vats. It also takes place in the bottle after bottling. The most important changes that occur are the slow chemical reactions that can allow complex flavours to develop.

 

  • For RED WINES, black grapes are crushed to release the juice, then the juice and skins are put in the fermenting vessel together. Fermentation takes place at a higher temperature for red than for white wine (20 ºC - 32 ºC). Alcohol helps the extraction of colour, tannins and flavours from the skins. In order to keep the juice in contact with the skin, the juice may be pumped over the floating skins or the skins may be punched down into the juice. The amount of color and tannin in the finished wine depends on how long the wine is kept in contact with the skins. This may be for more than 2 weeks for richly flavoured wines or, as little as five days for light wines such. It also depends on how much tannin, colour and flavor is in the skins – some black grape varieties are naturally light in color and tannins. Hot climates encourage higher colour and tannin levels in the grapes.

 

  • When enough color and tannin have been extracted, the free run wine is drawn off. The skins are then pressed yielding a further quantity of wine, known as the press wine. Press wine contains higuer levels of tannins, and may be blended with free run wine to produce the style required.

 

  • Maturation is the next step and can take place in barrels or large neutral wooden or stainless steel vats. It also takes place in the bottle after bottling. The most important changes that occur are the slow chemical reactions that can allow complex flavours to develop.

 

  • ROSE WINES must be made from black grapes. The method of production is similar to that for red wines but they are fermented at a lower temperature (12ºC - 22ºC). They must also have a much shorter period grapeskin contact (12 to 36 hours). Pink wines labeled as white Zinfandel are made this way.

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