He might be a one-man global industry, but sitting across from me at lunch he looks every inch the prosperous French country gentleman. He sports 'le look anglais' - blue blazer, blue-and-white shirt, navy sweater, dark trousers - and he drinks white wine from his private Bordeaux estate. Lunch, for whose simplicity he has apologised, is salad, smoked salmon, slices of cured duck breast, Serrano ham, a variety of local cheeses and paté de campagne made by his wife, a handsome blonde woman whose framed, life-sized portrait is the only adornment on the room's otherwise bare walls.

I take a sip of his Chteau La Grande Clotte - 'fine and delicate, astonishing', my wine guide says, a little over-excitedly, and, looking him in the eye ask, 'Would it be fair to describe you as a traitor to la république?'

Michel Rolland - for it is he, the world's number one wine consultant, the globaliser of the noble grape, a man whose influence, his detractors claim, is bringing the dead hand of standardisation to wine - does not fling the contents of his glass into my face. He does not splutter. He does not even blink. He smiles, rather. He shrugs. 'France is a great country, but it is not the only country,' he says, adding, with benign largesse: 'What wonderful things and wonderful people there are all over the world! Argentina, South Africa, California, Spain: wonderful! I derive great pleasure from travelling to these countries.'

Yes, but when he travels - he is away from France half the year - is he obliged to peddle to every Tom, Dick and Manuel the knowledge he has acquired over a lifetime applying mind, body and soul to the mysteries of Bordeaux wine? 'My life is my life. I do what I like to do. I have a job to do. My job is to do this.' To do what? 'To make good wine in order to make the consumer happy. When I began in this business 25, 30 years ago there were so many bad wines. Now there are so many good wines and, if possible, I want to help to make even more good wines all over the world. That is what I do.'

So he is not a great patriot, then? He smiles again, unapologetically, palms up, fingers splayed in the eternal Gallic gesture that says, 'that's the way it is'. So, would it be more correct to say that his first allegiance is not to France, but to the big wide world of wine? That wine, not France, was his country? He loves that. 'Exactly! Exactly right!' he cries, chuckling merrily. 'Bravo! That's it exactly! Wine is my country!'

There are people who say that, never mind France, it is actually wine that Michel Rolland has betrayed. People who love the grape as much as he does, or who would probably claim that they love it more, say that Rolland has sold out the ideals that have defined the millennial art of winemaking. A beautifully made documentary called Mondovino about the changes there have been in recent years in the global wine business, portrays Rolland, the man, in a generous light and shows him as the jovial fellow that he is. The man who made the film, Jonathan Nossiter, has paid homage to Rolland's importance by describing him as 'the Spielberg of wine'. But the film also lines up the old guard who revile him, allowing them generous time to direct their venom at an individual whom they despise - yet all agree to be the pre-eminent power in the world of wine; the oenologist whose formula for success has defined the nature of contemporary wine so comprehensively that his reach extends way beyond the 100 worldwide clients who have made him rich.

Aimé Guibert, a winemaker in the Languedoc, says wine is poetry, or maybe even religion. Hubert de Montille, who makes a very fine class of wine in Volnay, Burgundy, says wine stands for civilisation's defeat of barbarism. Rolland, they agree, is barbarism striking back. Artifice versus nature; globalisation versus local identity; the shock of the new versus the refinement of la vieille France. Romance, tradition and spirituality have no place, they say, in a Rollandian ideology subordinated entirely to the soulless demands of the market.

'Wine is dead,' says Guibert. 'Let's be clear wine is dead.' The reason wine is dead, he believes, is because Rolland has killed it, reduced it to one more product on a supermarket shelf. 'Rolland's line is this,' huffs Guibert. '"Great wines can be made anywhere." But there's just one rule that you must follow: consult Monsieur Rolland!'

These are not the isolated rantings of an angry old man. He and the other French traditionalists who take such grave offence at what they perceive to be Rolland's destructive pursuit of Mammon, or what Guibert calls his 'fascist monopoly' of the wine trade, are backed up by eminent figures in the global trade.

Take Michael Broadbent, author and wine director at Christie's in London. White-haired and venerable, in a Heseltinesque sort of way, he abhors the Rolland-inspired innovations that are reshaping, as he sees it, the sport he loves. 'This is a real problem,' says Broadbent. 'To what extent does individuality fly out of the window? I mean I think I'd rather have an individual wine that is maybe not up to scratch rather than a wine that is made in a glibly acceptable style, and rather innocuous.'

Broadbent argues that what Rolland is doing is transforming every wine he touches in the dozen countries where he operates into variations on the same theme: Pomerol, the wine region in Bordeaux where he comes from. 'He's making Pomerols in the Medoc. He's making Pomerols round the world,' says Broadbent. 'He won't admit this_ but he's making wines to the global taste.'

Neal Rosenthal's word for it is Napaisation, after the Californian wine region of Napa where, in recent years, Rolland's influence has also been powerfully felt. Rosenthal, a New Yorker who is one of America's leading importers of fine European wine, competes with Broadbent and Guibert in his rage at the Rolland machine. The core of the problem, as he sees it, is that rather than produce wine that evokes the terroir, the unique soil and place, where the grape was grown, the wine tastes the same whether it was made in Bordeaux, California or Chile. 'It's evil,' he says, through clenched teeth. 'It's evil!...In Bordeaux, the terroir is there, but they're destroying it. They're suppressing their terroir .'

Rolland thinks everyone is getting just a little carried away. 'Far too much importance is given to me,' he tells me over lunch. 'There are 300 million hectolitres of wine produced in the world a year. I just deal with a tiny fraction.' But has not his influence on quality wine been enormous? He shrugs and looks away, as if flattered.

OK, so what about the central argument of his detractors, that under his 'evil' influence, all wines are being Pomerolled, Napa-ised? 'The answer to that is very easy. I have done many many blind tastings of the wines made by my clients all over the world and if someone says to me that these wines are all the same, or even similar, I say, "please, be serious! Come with me and do a blind tasting and you'll see just how different they are, how the identity of each wine does indeed reflect the country and the region it comes from, and in a very clearly defined way".' But the master wine-taster Broadbent says they're all the same. That the Rolland formula requires that all wines be heavily fruited, with an edge of vanilla, velvety to the palate, low tannins, fermented in new oak barrels? 'Nonsense. There is no formula. This is not a valid criticism. This Broadbent fellow, I know of him of course, but I have never met him.'

For the only time during the four hours we are to spend together Rolland loses his smile. 'Broadbent, being a wine journalist, ought to speak to me before writing such things about me, don't you think?' he says. 'But he has never come to see me. He has never done a blind-tasting with me.'

Rolland's reply when I asked him why he thought he had so many critics, why they were so eaten up by him, was quite straightforward. 'I think those people are envious, more than anything else,' he says, beaming again. 'If the wine that I work with is not to their liking, there are loads more. I only have 100 clients. There are millions more winemakers out there. So why be so envious? Why be so disagreeable? I do my job with enthusiasm and goodwill. I make wine to give people pleasure. If others don't like this, well, never mind.'

Perhaps if Rolland had not made common cause with the Americans, the animus he inspires might not be quite so intense. Mondavi, a giant Californian wine firm that produces 100 million bottles a year, does look rather like a vinicultural version of Kentucky Fried Chicken when viewed by grizzled old winemakers in Bordeaux, Burgundy and Languedoc. Mondavi hired Rolland in 2001 to egg up its not entirely satisfactory Merlot line. They had noted with keen interest how Rolland's influence had helped radically improve the quality of a number of Tuscan wines, as well as some of the neighbouring competition in Napa Valley, and they wanted more of the same.

In his film, Nossiter does not shrink from portraying Mondavi and another Californian winemaker in a stark, crass light. Michael Mondavi, son of the Californian multinational's founder, says things like, 'We want to start a dynasty. Ten, 15 generations from now, it would be great to see our heirs making wine on some other planets. That could be kind of fun. "Beam me up, Scotty, send me some wine from Mars or something".' The likes of Aimé Guibert, meanwhile, come across as men genetically at one with their environment, as authentic sons of the wine soil.

In the wine culture wars, Rolland has positioned himself on the side of modernity. French by birth, he is American in spirit - a driving entrepreneur, irritated by the inefficiency of the old school, an eager embracer of technology. The dining room where we have lunch is brightly lit, white-walled, hard-floored, tucked away in the back of the functional building that houses his Laboratoire Vinicole in Pomerol, half an hour east of the city of Bordeaux. It is an odd place to encounter amid the bucolic order of the region's chateau-speckled vineyards, all the odder when you open the front door and step into a large antiseptic space peopled with silent, mildly sinister young men and women in white coats car rying out experiments with test tubes and beakers. The liquids inside the glass containers are all deep red. Rolland explains to me that winemakers from the entire Bordeaux region and beyond - some 800 wines in all - submit their products to continual scrutiny.

He roundly denies that there is such a thing as a Rolland formula, though he is prepared to accept that perhaps there is something that one might call a common denominator in the advice he dispenses.

'Look,' he replies, 'it is very simple - and at the same time very difficult - but from the first day I began studying oenology my objective was to improve the average quality of the wine that we drink. It was a particularly relevant task to try and embark on here in Bordeaux for the following reason. We had some very, very good wines, but also lots of poor ones. To be more precise, we'd had six or seven very good wines over the previous 70 years. And I thought, this is nuts! One good wine every 10 years? So I thought, surely we can improve on this. Surely we can drag the winemaking business out of the 18th century and bring it up to date with the technological age in which we live. It has to be possible to produce a very good wine more than once a decade.'

So what he did, he says, was pure common sense. 'I studied the history of the great harvests we'd had here in Bordeaux, I looked - to answer your question - for the common denominators. And what I found was that on those years there had been a lot of sun and low production. Very simple, very obvious. So I thought, OK, here are two factors that we can act on. What we'll do is lower the production and seek to harvest more mature grapes. Change the concept of ripeness, wait longer to harvest the vineyards.' So a key idea in the effort to overcome this problem of the notoriously erratic quality of Bordeaux wines, to stop them being so much at the mercy of seasonal fluctuations, was to endeavour to emulate years when there has been a lot of sun? 'That's right. Wait for the grape to mature rather than stick to a preordained date for harvesting that's independent of what the weather has been like that year.'

But also what is required is to 'green harvest', to pluck grapes early in the season so as to lower production, increase the intensity of flavour of the remaining fruit. And these techniques have worked. Irrespective of the gripes of the purists, there is a clear consensus in the wine world that the overall quality of Bordeaux wines has improved immeasurably over the last 25 years and that a lot of it has to do with the modernising influence of Rolland. Now even on 'bad' years a Bordeaux wine is eminently drinkable, and far more so than it was before.

'It's all perfectly logical, really,' he says. 'I am not a scientist. I am a man of peasant stock. I was born here in Pomerol, I have lived here all my life on a family farm that has 11 hectares of vines. I am a country boy, driving tractors from the age of 16. My brother and I, we studied originally with the idea of leaving the countryside because, as our parents saw it, it was too much work for too little return.'

Just as well Rolland decided to ignore his parents' advice. He is filthy rich now, owning wine farms in South Africa, Argentina and Spain, as well as Bordeaux, and with clients paying him fortunes for his commonsensical wine wisdom in a dozen countries, not excluding India.

'This is a part of my work that I love,' he says. 'Making wine in Pomerol is not hard. Making it in India is a challenge.' What happened was that in 1994 an Indian businessman came to see him in Bordeaux, told him of his quixotic ambition to make a decent wine in Bangalore. 'This gentleman said he loved wine, he loved France and French food. He told me he had been planting since 1988 but he'd had no luck. Could I come over and help him? I went and, indeed, it was a complicated business. There was no soil for wine, no tradition, no people. But we stayed with it for two or three years and now we are making some wine at the Grover vineyards in Bangalore - red, rosé and white - that are very pleasant. It has been a great achievement. Like a mountain climber who has scaled an impossible peak.'

The key point the Indian experiment helps make is the simple and glaringly obvious one that over the last 25 years or so, precisely the time that Rolland has been on the field of play, wine has evolved from being an elitist product to a mass market phenomenon. With increased volume there has come an increased demand for quality. To say that Italian and Spanish wines have vastly improved in the last two decades - not to mention Australian, Chilean, Argentine and South African ones - is to state the obvious. There is more wine drunk, and more good wine, now than ever, by far. And while Rolland may be careful not to exaggerate his role in this, there is a consensus that his counsel has spread beyond his immediate clients. His suggestions for green picking and delayed harvesting - as well as basic advice about replacing ancient barrels with new ones and throwing out rusting fermentation vats - have found ready audiences across at least four continents. As has the advice he has given to those anxious to accelerate the evolution of a good wine. The combination of the mass market and the arrival of new producers, not just in the New World but also in dynamic older territories like Spain, has resulted in a greater reluctance to lay down a wine for 20 years and wait to see what happens. (Though precisely because of the enormous growth of the wine-consuming market a bottle of top quality vintage that would have sold for £40 in 1980 now sells for £1,000.) People today want accessible, fruity, lush, smooth wines low in tannic acid that are not only high quality but ready in two or three years.

Is it not a pity, I asked Rolland, that wines have to be rushed out now the way they are? As a man who presumably loves wine every bit as much as your Guiberts and Broadbents, does he not feel a little guilty about the part he has played in the speeding-up process?

'Look, I repeat to you what I said earlier. I have to do my job. I do what my clients ask me to do.' Yes, but has not something been lost as a consequence of him satisfying the needs of his clients in California? 'I don't think so. I think this is another exaggeration. Because, first of all, we have never, ever had so many good wines. Never. It is also a fact that there are fewer bad wines in the world. And if that is not a good thing, well, I give up. Now, of course, I do love some of the great old wines. A '45, a '57, a '61. Of course I love them! But, how many of them are there?'

What also appears to be true is that Rolland's clients in the Bordeaux heartland - despite the fact that he is selling their secrets to foreign competitors - appreciate his services immensely. I accompanied him on his rounds after lunch, to three of the six cellars he had on his list for the afternoon. He had already visited another six that morning. Normally he travels in a chauffeur-driven Mercedes. This time he came in my car, with the Mercedes following down the narrow country roads, lined with geometrically planted plane trees. One reason he has a chauffeur, maybe the main one, is that at each stop he tasted six or seven wines. 'I taste on average 100 wines a day,' he told me. Which helps explain why he is such a master wine-spitter.

At our first stop, Chateau le Petit Village, the farmer in charge was a tall, fidgety man - clearly apprehensive to hear Roland's verdict. Rolland and the farmer took turns to taste half a dozen wines from the barrel, each at different levels of fermentation, and spat the contents out into a large white plastic bucket. The farmer's spitting technique was this: he leant his head directly over the bucket and emptied the the wine vertically into the bucket, but with a weak, messy dribble. Rolland's technique was something else altogether. He did not place his mouth vertically over the bucket. He stood slightly away from it, almost horizontal to the bucket's lip, before delivering a clean, clear spurt, strong, directed and practised as if he were a human fountain.

Rolland declared the first liquid he tasted to be a little serieux. The farmer frowned, shifted his weight more nervously from foot to foot. But the second was 'bon' and the third an emphatic, 'Oui, c'est bon', whereupon the farmer stopped fidgeting, stood taller, allowing a coy smile to cross his lips, like a proud father with a new-born child.

On the way to our next stop I ask him to explain what service exactly he had just rendered to the fidgety farmer. 'I suggest things he might do,' Rolland replies.' "We could do such and such," I say. Always the conditional, with wine. I never lay down the law. So in the case of the gentleman at Chateau le Petit Village all I suggested was that one wine might be ready for bottling in a week or so, another one maybe a little later.'

At Cote de Baleau, a cellar just three minutes away dominated by a formidably spired chateau, the farmer, a tall lady called Sophie, is more at ease with Rolland than the Petit Village man. They greet each other with laughter and kisses, like old friends - which they are, for they both went to school together. Three other members of madame's staff are in boisterous attendance.Yet, when the time comes to taste and spit, a hush descends on proceedings. Rolland is observed with solemnity as he swishes the red drink inside his mouth. He spits, he smiles, everybody smiles. 'C'est très bon' , he laughs. They all laugh.

He is like a country doctor visiting the neighbourhood patients. He makes check-ups on a constant basis, sampling and evaluating the wines at various stages in its pre-bottling gestation.

Just around the corner at Chateau Franc Mayne an intense young man in a purple-stained white coat, is an oenologist who treats Rolland with less awe than the others, but with the subtle deference a bright young consultant might have for a world famous specialist. The thought occurs to me that in any other context, in the smartest restaurant in London or Paris, these people who hang on Rolland's every word, would be considered mighty wine authorities, deferred to in their turn by the snottiest head waiters and sommeliers. Rolland is the maestro of the maestros. 'What I bring,' he says, 'is a range of experience and a span of reference that other people here, however talented they might be, do not have.'The purists, people on a stratosphere so rarefied that even the winemakers at Chateau Franc Mayne cannot breathe the air there, say that Rolland has abused his hard-won expertise. That he has put his talent to the service of the barbarians. There might be some truth in that, viewed from on high. But perhaps on balance he has done humanity a service by persuading the barbarians to do what most of them would not have imagined possible 25 years ago, to drink wine in the first place; to learn to do so on a regular basis; to develop a taste - even a stirring of familiarity - for your Merlots, Cabernets and Chardonnays, however crude and unsophisticated the hordes' palates may be in the eyes of the Broadbents and the Guiberts. They say he has sold out. Dumbed down. Killed the spirit of vive la différence. They accuse him of making wines 'to the global taste'. Maybe. Probably. But there are worse crimes.

Mondovino is out on 10 December