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

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.

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).

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.

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 grapefruit, lime and melon. During the wine-making process, the interaction of organic acids and alcohol forms compounds that imitate the aroma of other fruits.

Noble Rot is the result of the fungus Botrytis cinerea, and can have a strangely beneficial effect on the grapes. It tends to occur in places such as Sauternes in Bordeaux, and around the Neusiederlersee in Austria, where the vineyards lie next to large bodies of water. Early morning mists dampen the grapes, which are then burnt off by the afternoon sun.

Affected grapes become shrivelled and discoloured. Their water content is reduced, effectively concentrating the grape sugars. This results in a wine that has a rich, luscious texture, with concentrated, sweet fruit flavours.

Oak treatment such as barrel fermenting or barrel ageing was once considered a necessity. Now only an option, it can be used to add a taste component to wine. Well-judged use of oak can complement the other components; too much can overpower the fruit.

In general, oak maturation gives aromas of butter, toffee, caramel, vanilla, spice and butterscotch. French oak may give more buttery aromas, whereas American oak gives stronger vanilla and spice aromas.

However, there are many more variables that play a part in this process: whether fermentation takes place in the oak, or whether the wine is merely aged in oak; how long the wine stays in contact with the wood; how much of it is new as opposed to re-used; and how the oak has been treated.

Not all the natural fruit sugar in grapes is completely fermented. Most wines still have at least 1 g/l of residual sugar as some sugar compounds are resistant to the action of the yeasts. The level of sugar in the wine will determine how sweet it tastes, although obviously, this can be quite subjective.

The residual sugar in dry wine is usually undetectable, and most dry wines will have less than 2 g/l of sugar. However, some may contain levels of up to 25 g/l but will still taste dry due to the presence of tannin and acidity alongside the sugar.

Dessert wines will have the strongest concentration of sugar, some having as much as 250 g/l.

Tannins are a family of complex organic compounds extracted mainly from grape skins, and to a lesser degree from the pips and stalks. As the majority of tannin comes from the skin, this means that it is a predominant characteristic of red wines rather than whites. Tannins can be sensed by a puckering of the gums, or a furring of the mouth; a very similar feeling to drinking stewed tea.

The tannins give structure and backbone to the wine, and give it an added taste dimension. They are also essential if a wine is intended to age, as they act as a natural preservative.

Tannins are of more importance in the ageing of red wines rather than white. Great red wines are often quite tannic in their youth; with ageing the tannin softens and the simple, primary fruit flavours develop into complex flavours found in mature red wine.

Red wine with too much tannin is bitter and unpleasant, and its fruit flavours may be hidden beneath the tannins. The correct amount of tannin doesn't dominate other tastes, but gives the wine a little 'grip' in the mouth and seems to hold all the flavours together. A low measure of tannin makes simple, fruity red wine more suitable for quaffing than sipping.

Wine is mostly water; not added water, but water gathered naturally in the grapes. A wine may be described as 'watery' when the other components, particularly acids, seem too understated.

When a wine has finished fermenting, it will remain cloudy and contaminated with dead yeast cells (the lees). The wine needs to be clarified to separate it from the collection of dead yeasts.

However, wines that remain in contact with the lees for a long time can take on extra texture and richness, with biscuity, bready aromas and flavours. This technique is used to add an extra dimension to many Champagnes, white Burgundy, Muscadet and many other white wines. Some winemakers stir the lees (batonnage) in order to emphasise this effect.