The techniques that have cleaned up the making of wine are no secret. They include fermenting with single-strain cultured yeasts rather than wild strains, and preventing spoilage by chilling grapes and grape juice and using anti-oxidant additives.
Yet the latest trend among the young winemakers of California and South Australia is to question these squeaky-clean practices. They are using their training not to relegate old, low-tech practices to history, but to understand why they are often surprisingly successful.
Richard Gibson is group technical manager for the giant Australian Southcorp group, and much of his attention is given to re-evaluating practices which until recently were taboo.
"A big part of my job is looking at the techniques which are used traditionally to make great wine," he says. "It's trying to understand the basic scientific principles."
The key to making great wine, according to one school of thought in California, is to "dirty up" winemaking. This means permitting some oxidisation of the grape juice, followed by natural fermentation. Wild yeasts are used to ferment all the greatest French wines, from Chateau Petrus in Bordeaux to Romanee-Conti in Burgundy. Until recently they have been supplanted in the New World by strains of the sort developed originally by brewers and bakers.
But Southcorp - which makes Penfolds Grange, Australia's most celebrated red wine - is now experimenting with wild yeasts. So is Charlie Melton in the Barossa Valley and so too are leading Californian producers. Southcorp is looking at the effect of blending small quantities of naturally fermented wine with its regular production. One fear in the past has been of inadvertently introducing off-flavours such as acetic acid or the notoriously unpleasant hydrogen sulphide. But Mr Gibson thinks that in certain wines, and in tiny quantities, even anathematised substances may have a place.
"The Australian wine industry has gone to great lengths to ensure that its wines are free from hydrogen sulphide," he says. "It's a basic wine-making fault which shouldn't be present in detectable quantities. But it can be a powerful factor in contributing to complexity."
Complexity of flavours is the goal of many winemakers reacting against a world oversupplied from the same grape varieties - Chardonnay and Cabernet Sauvignon. "It's simply become boring," says Peter Vinding-Diers, the Danish-born and Australian-trained winemaker who helped to revolutionise the making of white Bordeaux. "You're seeing identical wines turned out all over the world."
Mr Vinding-Diers believes that local yeast strains, which mutate naturally to create a spectrum of difference, can contribute as much to a wine's uniqueness as variations in soil or climate. He carried out experiments in fermenting identical batches of juice with the naturally occurring yeasts found in different Bordeaux chateaux. Ten years after the wine was made, he says, students for the Master of Wine qualification have no difficulty in distinguishing them.
This is in line with analyses carried out at Oregon State University and by the Institut Co-operatif du Vin in the Rhone valley. These found quite dissimilar components in identical batches of juice fermented with different yeasts. However the debate is not over. Professor Ann Noble of the University of California has carried out "sensory difference tests" and concluded that yeast-derived flavour differences are relatively unimportant and fade with time.
The effect of oxygen is better understood. Many think of it simply as a potential cause of faulty wine. In a hi-tech winery, the war against oxidation begins even before the grapes are picked, with a treatment of ascorbic acid (vitamin C) or sulphur dioxide, continues with chilling of the juice, and ends with a final bubbling of nitrogen through the wine to drive out any trace of air before bottling.
But the world's greatest dry white wines in Burgundy have been produced for centuries in circumstances which make it inevitable that the juice will oxidise a little. The most fashionable Californian wineries have begun to imitate them.
The newer wine-making countries pride themselves on their open-mindedness. Without such an attitude there would be no great Australian wines; their history dates back to soon after the war when Max Schubert, the chief of Penfolds, toured the leading Bordeaux chateaux and returned having learnt about oak ageing and the value of oxidising red wines following fermentation.
Until now such receptiveness to others' traditions has foundered on the Anglo-Saxon cult of hygiene. It is difficult to picture Australians stripping off - as many Burgundians do - and plunging up to their necks in fermenting wine, even though technologyhas yet to devise as effective a way of macerating the grape skins in the juices.
But there is a new mood abroad. Australians in France enjoy moaning about the local willingness to use a proportion of grapes which damp weather has made mouldy with so-called grey rot. Yet on a recent visit to Champagne, Tony Jordon, head of Moet & Chandon's Australian operation at Green Point, was not fazed. "Maybe it's giving a bit of complexity," he said, adding, only half-joking: "Perhaps we should try and introduce some in Australia."Reuse content