You could argue that the discovery of the effect of yeast on grape juice was one of the mankind's most useful ones. Certainly wine has given a lot of people a lot of pleasure for thousands of years. But you could also argue that a more recent discovery has given wine-drinkers something rather special that wasn't available to the drinkers of old. That discovery was secondary fermentation in the bottle.

Although it isn't the only wine to go through a secondary fermentation, the process is best known by the name 'Champagne'. Until the seventeenth century Champagne, a little to the north of Burgundy, made rather acidic red wines which were overshadowed by their more illustrious neighbour. The credit for transforming the production of Champagne wines to sparkling whites has traditional been given to Dom Perignon, the cellarer for forty seven years in the Abbey of Hautvillers. He didn't invent the process for making the sparkling wine, but he popularised it and by judicious blending of the abbey's grapes produced wines that were far superior to anything that had been made up till then. We can give him the credit for putting Champagne on the wine map.

Champagne begins it life as the Pinot Noir grape, the same grape of the great Burgundies. But it's only the skin and flesh of the grape that is coloured, the juice is white. Red wine takes its colour during the fermentation process from the skins, but in Champagne the free-flowing juice from the crushed grapes - the cuvee - is never left in contact with the skins, hence it never absorbs the colour. This cuvee is fermented in the usual way and makes a simple white wine. The magic comes next. In early spring of the year following the harvest this wine is given a little extra sugar - the dosage - which with the rising spring temperature starts the fermentation process once more. But this time the carbon dioxide by-product of fermentation is trapped in the bottle by a cork and is slowly absorbed by the wine, building up pressure inside, which is why Champagne bottle are so thick and strong. More sediment forms during this secondary fermentation which is removed by 'remuage'. This is the time-consuming practice of giving every bottle a sharp twist and slight lift every day. Bottles begin on their sides, but by the end of the 'remuage' they are vertical with the necks downwards. The sediment will now be on the inside face of the cork.

The next job is that of the 'degorgeur' who extracts this cork with the sediment, while losing little of the precious liquid. The 'doseur' comes next and he adds the 'liqueur d'expedition' which combines sugar to sweeten the wine if necessary and a little brandy to stop the fermentation. Then it's corked again with the familiar cork and it's ready for shipping.

Most Champagne houses have mechanised much of the process that I've described, but one holds to the old ways - Bollinger. It's also unique in that it produces 70% of the grapes that it needs in its own vineyards, with the rest bought on long-term contracts. Many houses have few vineyards, while Piper-Heidsieck and Gratien have none at all. Most Champagnes are the blended produce of many growers, whilst Bollinger resolutely soldiers on alone.

Wine of the Week.

Bollinger Grande Anne.