From terroir to table

First you need land. Nothing the winemaker does influences the taste of wine quite so much as the grapes and the conditions in which they are grown. But where to plant? And no, the Scottish islands won't work, whatever your fantasy.

Location, location
The wine-producing regions of the world lie in two sharply defined bands around the globe: the moderate, temperate zones that lie between 50¡ and 30¡ in the northern hemisphere, and 30¡ and 50¡ in the southern hemisphere.

It always used to be that cooler areas away from the equator made the best wine, while hotter areas produced high-yield wines made for glugging. But things have changed. Technology has advanced; winemakers have wised up. Those in hotter areas now have all kinds of tricks up their sleeves - such as picking the grapes earlier and managing the vines better.

In general, though, the nearer you get to the equator, the more difficult it is to produce decent wine (though that doesn't stop Japan, and even Thailand). Tropical rain means nasty fungal diseases and, because there's no winter, the vines don't get a chance to rest, which means artificial seasons and barely ripe fruit.

Too much rain isn't good in cooler-climate regions, either, so the sunniest spots are sought out. The best in the northern hemisphere are on south-facing slopes, which soak up any rays going. And you need sun, because there has to be enough sugar in the grape to be converted, by yeast, to alcohol.

Then, of course, there are other hiccups brought about by the weather - frost and hail for starters, which can wreak havoc during vine flowering in late spring. Too much sun? Then irrigate. Many New World vineyards wouldn't exist without irrigation.

An earthy business
Soil. Such a simple word, isn't it? But the soil - or rather the drainage of the soil - will affect the taste of the wine. Take Chardonnay, for example. Grown in Chablis (you remembered that Chablis is made from Chardonnay, right?) on limestone soils, the wine will have a flinty, mineral quality; but Chardonnay grown in California's clay soils will taste much heavier.

But where to plant? The ideal spot is halfway up a hillside, where grapes get the most sunshine and the best drainage. Vines planted on the flat get less sunshine, drain badly and are prone to frost. Plant vines too low down the hill and they may suffer from the damp, especially if there is a river near by. What about the top of the hill - after all, the view's good? It's too cool and too windy, and if there are trees on top, then it's not sunny enough. Got it?

Growing up It's been a perfect growing season. The vines had a good sleep through winter, and pruning was successful. It's important to get this right, as the grower can decide on his yields (see panel) for the year and determine the number of bunches each vine is to produce.

He had already worked out the density of vines he wanted per hectare. Northern France, for example, can achieve vine density of up to 10,000 vines per hectare, whereas the arid plains of Spain, where the vines need to work a larger area of soil to suck up the moisture, manage about 1,400 plants per hectare.

The spacing of the vines is an issue, too. Old World vineyards tend to have enough room for a person, or a specially adapted machine, to move about between the vines. Many New World vineyards are set up for machine picking, with rows up to 3m apart.

Then he has to decide how he will train the vines. The most popular way is along wires. It controls the vigour (leaf count) of the vine, which in turn prevents the spread of disease, and it lets the air circulate. There are all kinds of ways to train a vine, with names such as "single guyot", "Geneva double curtain" and "gobelet".

If the grower is lucky, he will sail through without a spring frost, which can damage or destroy the shoots emerging from the buds left on the vine (vines are damaged at temperatures below -5¡C).

And if he's lucky, flowering goes well too, lasting for a week or so, then the summer sun transforms the hard, green pellets to fat, juicy fruit. OK, so the grower might have had to do a green harvest (crop thinning) to let the remainder of the grapes ripen better, and he might have had to cut the leaves back a little to allow the sun to get at the fruit. This is known as canopy management. It shapes the vine, exposing the grapes to the sun's ripening rays when high rainfall has prompted growth spurt.

Then, hopefully, after a smattering of summer rain to protect against the drying effects of the sun, the grapes are ripe and ready to pick.

Make wine, not war
Now, here comes the best bit: making wine. Any decent winemaker can make drinkable wine from OK grapes, but it takes some talent to make stunning wine from good grapes.

Actually, at first glance, making wine is pretty straightforward. As soon as the grape skin splits, the sugary juice on the inside comes into contact with yeasts that live naturally in the air and on the surface of the grape skin, converting the juice into alcohol. This is known as fermentation.

Of course, things are never really quite that easy, and many different factors come into play. Constant experimentation with equipment and techniques is what winemaking is about today. But we like simple, so here goes: to get the juice, you need to break the skin of the grapes in a crusher. If you're making white wine, the next job is to get the fermenting juice away from the skins and stems as soon as you can - you don't want any colour or tannin in your white wine.

Then you transfer the crushed grapes to a press, squeezing out all the juice and pumping it into a container called a vat to ferment. Some winemakers put whole bunches straight into the press to get even fresher juice.

Temperature-controlled fermentation (read cool fermentation) is the single greatest advance in winemaking in the last century. It meant lots of lovely, fresh, fruity wine, even from hot-climate countries such as Oz. Most glugging whites are made in big temperature-controlled vats, with some top dry whites fermented in small oak barrels, which add a buttery, vanilla-laced richness to the wine.

Red wine is made by fermenting the juice and skins together, since it's the skin that contains all the colour, flavours, aroma and tannin; and it's usually done in stainless-steel vats, concrete or sometimes wood.

The fermentation temperature reached is much higher for red wines, to get as much colour and flavour from the skins as possible. And the vat will have to be stirred, or pumped over, to get maximum skin contact. Then, when you have enough colour, tannin and flavour, the juice is drained off the must into a fresh container.

For ros‚ wine, the juice is separated from the skins much earlier, so it has just a smidgen of colour. Then it's treated just like white wine.

Fermentation is complete when all the sugar in the wine has turned to alcohol, or the alcohol level is high enough to kill the yeasts. Blending can happen at this stage, and then it needs to be matured for anything from a few days to a few years, depending on what kind of wine you're going for. Bung the wine in small oak barrels - or use the cheap method: pass it over oak chips - and watch the rich, toasty flavours develop. The newer the barrel, the greater the flavour.

But be warned: barrels are not for every grape variety. For the likes of Sauvignon Blanc and Riesling, say, stainless steel rules, as it allows their fresh, fruity flavours to come through.

Bubbly, of course, is made rather differently. The Champagne method is best, and the wine needs a second fermentation in the bottle, before whipping it off the sediment (dead yeast), adding a little sweetening to curb the acidity and stoppering it with a cork - all this without losing any precious bubbles.

For sweet wine, there must be sugar left in the wine after fermentation (residual sugar). The simplest, and cheapest, way to stop fermentation before all the sugar has turned into alcohol is by using a centrifuge or a filter. The good stuff, though, needs super-ripe grapes. The most intense are those affected by a fungus called noble rot (botrytis), so that the yeasts cannot ferment all the sugar before the alcohol kills them off.

And let's not forget fortified wines. Sweet or dry wines with 15% alcohol or more are usually made by adding brandy or pure spirit to the wine, and were originally developed so that they could travel well - think port and sherry. There is a particular method for producing dry sherries (fino and co), which involves growing a layer of yeast, known as flor, on the wine's surface, giving it its typically nutty, salty tang. n

Yields
The quantity of wine produced from grapes is measured in Europe as hectolitres of wine per hectare of vineyard (in the USA, it's measured as tons of grapes per acre). The figures are also affected by the characteristics of the grape, what sort of wine is being made and how hard the grapes are pressed. The best wines are made with grapes produced in low yields, especially in cool climates.