If a hunter-gatherer of a couple of millennia past collected bunches of ripe wild grapes and left them in a container, a wonderful thing happened. As the liquid was pressed out of the grapes by their own weight, the natural yeasts present on the skins began to digest the sugars in the must. The main by-product of this digestive process is what we know as alcohol. The most basic of wine is no more complicated to make than I've just described - it happens in an entirely natural way.

Wine-making man, however, wanted always to improve on the basic, and very variable, drink. One of the first attempted improvements was increasing the alcoholic content of the wine. The principle here is quite straightforward; the more sugar you have in the grapes, the more alcohol you get after fermentation. There's a limit though, the yeasts can't survive in a liquid with more than 16-17% alcohol by volume, so that's when fermentation stops. But that's quite enough alcohol to make a very strong wine.

There are various ways to achieve this, the most simple being the use of only very ripe grapes. That's easy enough in hot climates, but in regions where sunshine is more variable, the easiest solution is to add sugar to the must. Simple and effective as this is, it's an illegal practice just about everywhere. Wine-makers have to look to other methods to stay within the law. One very effective technique is to let your grapes shrivel in the sun. This lets some of the water present in the grapes evaporate through the skins, while leaving behind the sugars. Now you have less liquid for your wine, but the sugar content is a much higher percentage.

With a very high sugar content in the must the wine-maker has several options, one being to let the fermentation finish naturally when the yeasts have done their job and there's no sugar left, leaving you with a highly alcoholic wine. Another is to stop the fermentation, leaving you with a wine of normal alcoholic strength - anywhere between 12% and 14% - and still leave some sugar in the wine. Some of the better dessert wines are made like this. Another technique is that used by Port makers; here they add brandy to the wine to bring its alcohol content over 17% and thus stopping fermentation, while leaving residual sugars to give the sweet taste.

In the area around Lake Garda in Italy where Soave and Valpolicella come from, they make Amarone. It's an expensive wine because only the outermost grapes of each bunch are used, the ripest ones with the most sugar. These are then partially dried to concentrate the sugars and are then made into the Recioto Amarone.

Wine of the Week

Ripassa 1998, Zenato.

Made in the same area and in much the same way as Amarone, Ripassa makes a budget alternative to one of Italy's most expensive wines. Velvety and full of character, it does need to be opened a couple of hours before drinking and chambreed, but don't drink it at over 20 degrees celsius.

RRP £12.99. Available Searsons, On the Grapevine, Michael's Wines and selected off-licenses.