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How Wine is Made

The making of wine is an extremely complicated business - winemakers often study a degree in 'oenology' before embarking on their careers. Winemaking is a mixture of farming, art and science.

The important aspects of how wine is made are of course those that have the most significant impact on what the finished wine actually tastes like, so from a consumer point of view only the basics are really worth worrying about, which is what we focus on here.

Obviously the first stage in making wine is growing grapes. Many of the flavours in a finished wine are a product of flavours found in the grape juice that makes it; features such as the grape variety, the climatic conditions in the vineyard, and even the type of soil and the style of 'training' of the vines can have an impact.

But the human element is also important, and the various differences in the way grapes are turned into wine can have a marked impact on the flavour of the wines we drink. Winemakers control things like fermentation, pressing and oak ageing to craft their product.

The production of sparkling wines such as Champagne is a fascinating variation on the normal process, steeped in myth, mystery and history. If you ever get the chance to visit a Champagne house or sparkling wine producer then do - they can be fascinating places.

Growing Grapes

It's easy to forget when looking at expensively packaged fine wines in wooden cases or undoing the screwcap on a chilled bottle of Sauvignon Blanc that wine is an agricultural product. Wine is fermented grape juice - pure and simple. Just as top chefs place great importance on the quality of their ingredients, ask any winemaker how to make great wine and they'll tell you that most of the work is done in the vineyard.

Terroir

Different varieties of grapes have different flavour characteristics. In many parts of the world this is considered the most important factor, and so wines are labelled according to their grape variety, such as Cabernet Sauvignon or Chardonnay.

However, there are other things that affect the flavour of grapes and the wines made from them. Hot, sunny climates produce riper grapes with more sugar which generally make richer and more full-bodied wines. Other factors often considered include the type of soil the vine stands in, the vineyard's aspect to the sun, and the practices followed in the vineyard.

The French have a word that sums all this up, terroir. Most French wines (and many from elsewhere in Europe) are labelled according to where they come from rather than the grape variety used to make them. In regions such as Burgundy and Bordeaux they go even further, with vineyards classified into differing "quality" levels according to their terroir.

The Grapevine

The grapevine is a climbing plant that is unable to support itself, which is why almost all vines are planted using some form of trellising. The neat, orderly rows of vines that form part of such famous landscapes as Chianti in Tuscany and the Loire Valley are a result. The exception to this is "bush" vines, which are left free-standing but very low. These are most commonly in warm regions such as Châteauneuf-du-Pape and Rioja, and especially for the Grenache (or Garnacha) grape variety.

The annual cycle of grape growing starts in the winter, when the vines spend the cold months lying dormant. Vine growers (vignerons in French) are anything but dormant however, since there is important pruning to be done. There are many baffling variations of pruning and training techniques are often governed by local tradition and even by law.

In the spring the vine bursts into action, with new, spindly shoots beginning to form as the days warm up and lengthen. At this time frost is a big risk, since it can kill these young shoots and so decimate a crop, such as in Bordeaux in 1991.

Flowering occurs in early summer. A vine's flowers are not very pretty to the eye and look like miniature cauliflowers. Fortunately, they do not need to attract insects either, since fertilisation of the flowers is by wind pollination, although this does mean that poor weather at flowering time can again damage a harvest.

During the summer the vine continues to grow: leaves develop, and berries (which will eventually become grapes) form. The crop yield, which many people regard as key to the quality of the finished wine, becomes important, as the more fruit the vine produces the lower the level of flavour compounds in each grape. For this reason, a "green harvest" may be carried out to remove excess fruit.

As grapes ripen their acidity levels drop and sugar levels increase. A well-known generalisation is that harvest will take place 100 days after flowering although this varies by grape variety and climate - the warmer the weather the faster grapes develop. Quality-conscious vignerons try to pick at optimum "physiological ripeness", when the flavour components of grape juice peak and so give the most flavour the resulting wine.

Grapes can be harvested by hand or machine. Machines are faster and more cost-effective for large vineyards, but are not suited to difficult terrain such as in the Mosel Valley in Germany or Douro Valley in Portugal. Also, machines are not selective, so for many top wines hand-picking is preferred since poor fruit can be rejected.

Making Wine

Here's an interesting fact: turning grapes into wine is entirely natural and can occur without any human intervention at all. If grape juice comes into contact with airborne yeast it will ferment. Easy, isn't it?

Well, no, not really - which is why many modern wineries look like space-age facilities, gleaming with stainless steel tanks and industrial equipment of all shapes and sizes.

Receiving Grapes

Because grape juice is colourless, all the colour in red and rosé wines comes from the skins. There is therefore a difference between how white, red (and rosé) wines are made. Strangely it is even possible to make white wine from black grapes (such as when making Champagne).

For white wines, the grapes are pressed to separate their juice, known as must, from the skins and pips as soon as they arrive at the winery, while for red and rosé wines the skins and pips are retained. There are all sorts of different presses for this job, from picturesque wooden "basket" presses, to sophisticated machines that use a slowly inflated rubber balloon.

The juice and skins may only remain in contact for a few hours at a cold temperature for pale rosés, or for many weeks (until after fermentation has finished) for serious reds, allowing time for the skins' colour and other flavour components such as tannins to infuse into the wine. There are a number of techniques to control this extraction, such as pumping juice over the floating "cap" of skins, holding or pushing the cap down into the juice, or agitating it with panels. The skins may even be pressed afterwards to extract even more tannic structure.

Fermentation

Without rehashing school science lessons, fermentation is a chemical process where yeast turns the sugars in the sweet grape juice into alcohol and carbon dioxide. The yeast may be naturally occurring on the skins of grapes and in the air, especially in areas with long traditions of winemaking, or a specific yeast culture added by the winemaker for a more reliable and predictable process.

Winemakers may choose to control the process in a number of other ways. Fermentation generates heat, which speeds up the extraction of colour, tannins and flavour from skins and pips in red wines but can also affect the delicate aromatic compounds in the juice. Winemakers usually try to reduce the temperature, especially when making white wines, to preserve these aromas.

Some high quality wines are fermented in expensive oak barriques, the small barrels naturally regulating temperature as well as imparting some oak flavour to the finished wine. A much more variable process, this needs careful monitoring to make sure everything works to plan and is usually therefore only used for luxury wines.

Maturation

Fruity white wines are then ready for filtering and bottling, but for many serious wines a further maturation process is begun, sometimes lasting several years, and usually done again in oak barrels. Oak is a great material for ageing wine because it is not completely airtight and allows a very small amount of oxygen to interact with the wine. This softens wines and can add complexity, especially over a long period of time. The style of wines such as red Bordeaux and Rioja depend on this.

However, oak can also add its own flavours to the finished wine, and controlling this is one of the most important (and occasionally controversial) decisions for the winemaker. The level of oak flavour depends on a number of factors; newer barrels impart much more oaky flavour than those that have been used a number of times; barrels are "toasted" to different degrees; the wine can be "racked" from barrel to barrel with differing degrees of regularity and there is even a difference between American and French oak.

Other Techniques

The list of other variations and optional treatments that winemakers can use is mind-boggling. They could micro-oxygenate the must, use a reverse osmosis machine, or ferment using carbonic maceration. They will almost certainly fine the wine, and they may or may not filter it. Some may even pasteurise their wine. All may have very small, but perceptible, affects on the wine.

However, worrying about the minutiae of the winemaking process is not the best way to appreciate wine – by far the most important aspect is the end result, how it tastes

 

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