What's in the Glass?

To really understand and enjoy wine, it helps if you can appreciate the role that the balance of alcohol, tannins, acidity, flavour and other components make in producing the finished product. It is up to the winemaker who manages the process from vineyard to bottle to manipulate these components to produce their desired style of wine.

• Acid
• Alcohol
• Carbon Dioxide
• Fruit
• Noble Rot
• Oak
• Sugar
• Tannin
• Water
• Yeast

Acid

Tartaric, malic and citric acids naturally form in grapes, and together they form the wine's 'acidity profile', which is balanced by sweet components. After fermentation, the malic acid may be converted to lactic acid through bacterial activity, in a process termed malolactic fermentation. The alcohol in wine may be converted to acetic acid (vinegar) by acetobacters, another bacteria found in wine.

If a wine has too little acidity, it will seem dull, flabby or perhaps cloying, especially in a sweet wine. If it has too much, then the wine will be harsh and sharp.

Wines from cooler regions, such as Northern France or New Zealand tend to have high acidity. Grapes harvested in warmer countries such as Australia tend to have low acid profiles, which are sometimes low enough to warrant chemical acidification.

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Alcohol

Alcohol is produced in wine by the fermentation of the natural grape sugars by yeasts. This means that the more sugar in the grape, the higher the resulting alcohol content will be. In cooler climates, grapes can struggle to ripen, and sugar levels will be minimal. Consequently such wines may only reach 7 or 8% strength.

The upper level of alcohol is determined by the yeast itself, rather than the amount of sugar. In warmer climates, the grape may be packed with sugar, but once the alcohol level reaches about 14%, the yeasts can no longer function and rapidly die off. Consequently, wines with a strength of more than 15% will undoubtedly have been fortified.

Glycerine is a complex alcohol; another by-product of the fermentation process. This component gives wines a desirable degree of viscosity (thickness).

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Carbon Dioxide

This gas is produced during fermentation, and it is allowed to escape in the production of table wines. However, some dissolved carbon dioxide may remain in the wine, giving it a slight 'fizz' (known as pétillance). This can be considered a positive attribute in, say, an otherwise uninteresting rose.

However, a minor second fermentation can sometimes take place after bottling, and the wine is ruined by the undesirable prickle.

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Fruit

The beauty of grape varieties, both red and white, is their ability to produce wine with a complex aroma of fruits other than grapes, particularly when young. Each grape varietal has its own set of typical fruit associations. Cabernet Franc may impart fruit flavours of raspberry, cherry, plum, and strawberry, whereas Sauvignon Blanc will have fruit profile of g...

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