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The Components of Wine

I must confess that I had been drinking wine, with quite an interest, keeping tasting notes and scouring retailers for certain wines that I wanted to try, long before I paid any attention to anything other than the flavour of a wine. Even when I heard other more experienced tasters talk about tannins and acidity, I was still somewhat bemused as to what they where referring to. Realisation only began to dawn when I really began to pay attention to the structure of a wine, rather than just the flavour. An appreciation of the balance of tannins, acidity, alcohol, flavour and other components did much to help in my understanding and enjoyment of wine. Self-education regarding taste is, however, difficult. My first taste of a three year old classed growth claret did a lot to tell me about the effects of tannin on a wines drinkability and longevity. I hope this brief guide to the components that make up a wine will help you to understand and enjoy them more also, without having to pop open too many expensive wines as part of your learning!


The tannins in a wine are derived from the pips, skins and stalks. They are vitally important if a wine is intended to age, as they are a natural preservative. The tannins give structure and backbone to the wine. They can be sensed by a furring of the mouth, or puckering of the gums, a sensation very similar to what happens on drinking stewed tea. This is unsurprising, as this effect is also due to tannins, released from the tealeaves after stewing in the hot water for too long.

Tannins are of more importance in the ageing of red wines rather than white. The tannins act as a preservative, and as they fade over many years, the simple, primary fruit flavours have time to develop into the more complex flavours that are found in fine, aged wines. A level of tannins that is sufficient to provide structure, but not so obvious as to dominate the palate, is the ideal when a wine is ready for drinking. For this reason tannins are still important in red wines not intended for long ageing, as they give grip or structure to these wines also. Tannins may also have different qualities, and may be described as harsh (especially in a wine drunk too young, such as a young classed growth claret), soft (eg. Beaujolais), stalky, chalky, etc.


All fruit requires acidity, be it an apple, lemon, mango or grape. Acidity is what gives fruit its refreshing, flavoursome sensation. Without it fruit would seem overly sweet and cloying, a little like the sensation derived from drinking the sugary fruit syrup in which some canned fruit is presented. Just like fruit, wine also requires acidity. Too little, and it will seem dull, flabby or perhaps cloying, particularly if it is a sweet wine.  Too much, and the wine will be sharp, harsh and undrinkable. Acidity can be detected by the sharpness of the wine in the mouth, particularly around the edges of the tongue near the front.

Some acids, such as acetic acid, are known as volatile acids, and in small amounts these can really lift the flavours in the wine. Too much, and the wine begins to resemble furniture polish, acetone (nail-polish remover) or even vinegar. Higher acidity denotes a wine from a cooler region, such as Northern France, England or New Zealand. Low acid wines come from countries with warmer weather, such as Australia, where acidity in the harvested grapes is often low enough to warrant chemical acidification.


Alcohol is the product of fermentation of the natural grape sugars by yeasts, and without it wine simply doesn't exist. The amount of sugar in the grapes determines what the final alcohol level will be. In cool climates, such as Germany, where the vines struggle to ripen their grapes, sugar levels will be minimal, and consequently such wines often only reach 7 or 8% strength. In very warm climes, however, the final alcohol level will be determined not so much by the amount of sugar but rather by the yeasts themselves. Once the alcohol level reaches about 14% the yeasts can no longer function and rapidly die off. For this reason, wines with a strength of more than 15% are almost certainly fortified.

The conversion of sugar to alcohol is such a vital step in the process of making wine, that the control of fermentation is the focus of much of the attention of the modern winemaker. Fermentation generates heat, and a cool, controlled fermentation will result in very different flavours in the wine (in particular, it protects fresh, delicate fruit flavours) when compared with wines where fermentation is allowed to run riot. Although fermentation will start naturally, thanks to yeasts naturally present on the grapes in the vineyard, some winemakers prefer to remove the element of chance this involves by kick-starting fermentation using cultured strains of yeast. This can have problems though - cultured yeast strains have been blamed for some unusual characteristics in wine, such as banana flavours in Beaujolais.


Following on from the above, it is clear that if fermentation is arrested, either as a result of the yeasts failing in a gradually increasing alcohol level in the ferment, or as a result of mans intervention, there will as a consequence be some remaining sugar in the wine. Even when the yeasts work is unhindered, most wines still have at least 1g/L of residual sugar as some sugar compounds are resistant to the action of the yeasts. Clearly, the level of sugar in the wine determines how sweet it tastes. This is quite subjective, however, and even wines that taste very dry have some degree of residual sugar. Most dry wines have less than 2g/L of sugar, although levels of up to 25g/L may be present in wines which still taste dry due to the presence of acidity and tannin alongside the sugar. The greater the amount of residual sugar, the sweeter the wine, moving through demi-sec (Champagne) and off dry wines (many German Rieslings) to the dessert wines of the world (Sauternes, Tokay, etc). Some of these have incredibly high concentrations of sugar, as much as 250g/L.


Many wines are matured in oak barrels, and some are even fermented in oak. Oak from different sources (most comes from either the forests of France or USA) will impart different characteristics on the wine, but 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, although but there are many more variables in the equation than this simple statement suggests. It all depends on how much oak is used, how much of it is new as opposed to re-used, how long the wine stays in contact with the wood, whether the wine is merely aged in oak or whether the fermentation takes place in it, how the oak has been treated, and so on. For instance, barrels that have been 'toasted', which means the cooper has formed them around a small fire, often burning the oak shavings he has produced in the manufacturing process, will have aromas of smoke and toast. Barrels that have been steamed during manufacture, however, may give more oatmeal aromas.


Noble Rot, the result of the fungus Botrytis cinerea, has a peculiarly beneficial effect on the grapes. It tends to occur in vineyards that lie next to large bodies of water, where morning mists dampen the grapes in the morning. Such locations include Sauternes in Bordeaux, and around the Neusiederlersee in Austria. Following this the mists are burnt from the ground by the afternoon sun. In conditions which are too damp, where the mists persist all day, the grapes are much more likely to be affected by Grey Rot, a destructive fungal infection which has no beneficial effect at all.

Although grapes affected by Botrytis look terrible, discoloured and shrivelled, they are the starting point for making some fabulous wines. The Botrytis has the effect of reducing water content in the grapes, concentrating the grape sugars. The quantity of wine is thus reduced, one reason touted for the cost of these bottles. Another is the need for careful selection of botrytis-affected grapes, requiring large numbers of pickers making numerous passes through the vineyard during the harvest weeks. The wine that results has a rich, luscious texture, with sweet, concentrated fruit flavours.


In many wines the yeasts themselves are the cause of certain flavours. When a wine has completed fermentation it remains cloudy and contaminated with dead yeast cells. Many different techniques are employed to clarify the wine, including racking the wine  (gently pouring the clear wine off once the dead yeast cells have settled to the bottom) from its lees (the collection of dead yeasts).

Wines that remain on the lees for a long time, however, will take on extra richness and texture, with bready, biscuity aromas (and flavours). This technique is employed to add an extra dimension to many Champagnes, as well as Muscadet, white Burgundy (including some Chablis) and many other white wines. Some vignerons practice batonnage (stirring of the lees) in order to accentuate this effect.


After this assessment of all the components present in wine, it is still necessary to examine the flavours that are present. In young wines at least, the flavour is directly related to the grape variety used. For more details see my section on classic white and red grape varieties.