Peterson, who set up Ravenswood back in 1976, believes Californian wine is heading in a "new direction" with the advent of younger winemakers.

He said newcomers were coming into a "whole new world", with huge international ranges of wine now widely available. They have much easier access to the market as they can sell online, and receive payments instantly to help finance new projects. "They can determine their own destiny," he said, adding that many could look at making and selling wine that previously would not have worked commercially, since they can handpick and market to a select audience.

His son, Morgan Twain-Peterson, who also runs his own winery Bedrock, is experimenting with Albarino, white Bordeaux styles, Sauvignon Blanc in a Sancerre style, Cabernet Sauvignon grown on "a patch of rock on the top of a mountain" and even sparkling wines, said Peterson.

These new young winemakers are "breaking the mould of what we would consider Californian wine".

"The future is really strong," Peterson added, "we're reaching a time when there will be a changing of the guard," as some of California's big-name wineries begin to be sold off. "Whether they go to huge organisations or individuals remains to be seen."

Speaking at a lunch held at London's Vinoteca yesterday, Peterson said he was not yet sure that lower alcohol wines where what consumers wanted.

"People are talking and writers pushing towards bringing alcohol levels down [in Californian wines], but it remains to be seen whether that's people's preference. The last two vintages, 2010 and 2011, were very cool and that forced winemakers' hands - they had to pick earlier. If [that style of wine] ends up popular, then they will stick with that."

But he said the 2012 harvest produced about 30% more than average, and was later ripening, "it was a very even year, but we feared we would never get [the grapes] ripe".

"Winemakers could pick when they wanted and you didn't have to be much of a winemaker to make a good wine," added Peterson, warning that while most of the wine was great quality, "there will be only a very small percentage of exceptionally superb wines".

"It wasn't that kind of vintage," he said.

He said the vintage was a "godsend" following two "winemaker's vintages". "2010 and 2011 were short and there was less wine in the coffers. This vintage will only just bring it back up to parity. We were getting to the point where there was more demand than wine. This year growers get a price and volume increase."

To read more about Peterson, see Gemma McKenna's blog on blending the ultimate Zinfandel.