Noble rot

Making sweeter wines with moldy grapes

<i>Botrytis cinera</i> on the vine in the Sauterne district of France.

Botrytis cinera on the vine in the Sauterne district of France.

PHOTO by edwin leung (via flickr)

In the fall of 1985, a young winemaker in Forest Ranch named Phil LaRocca discovered that his zinfandel vineyard was fouled with mold. It seemed the crop would be lost, until a friend—a winemaker visiting from France—told LaRocca that there was hope: Let the grapes fester, he advised, and harvest them in November.

LaRocca did just that. He fermented the juice, and he wound up with a standout batch of rich, red dessert wine—and he couldn’t have made it without the fungus.

Because Botrytis cinerea isn’t just any nasty fungus. This mold, recognized by most grape growers as both friend and foe, is also called “noble rot” and was first cultivated on ripening grapes by French and Hungarian winemakers. Though Botrytis can destroy a vineyard of fruit if it over-develops, it is also responsible for some of the finest, most delicious sweet wines in the world.

Since that first vintage, LaRocca has produced a late-harvest botrytized zinfandel almost every year. The mold requires a delicate balance between moisture and sunshine all the way into November. In ideal conditions, the mold shrivels the grapes and intensifies sugars and flavors. Fruit yield decreases as the juice grows syrupy, but the wines that result from a Botrytis infestation can be wonderful.

“There is an elegance on the finish that only comes from the Botrytis,” said LaRocca, who owns LaRocca Vineyards. “But it’s a gamble, because by letting the mold grow you risk losing your entire crop if it doesn’t rot just right.”

French winemakers depend on Botrytis cinerea to produce the dazzling flavors and aromas that make sauternes among the most sought after white dessert wines in the world. Sauterne, which is named after a district in France near Bordeaux, is made from sémillon, sauvignon blanc, and muscadelle grapes. Aged several years in oak barrels, a classic sauterne is golden colored, redolent of honey and pineapple, about 13 percent alcohol, and as sweet as a peach.

LaRocca uses a red grape for his botrytized wine, and so his sweet late-harvest zinfandel, available at S&S Organic Produce and Natural Foods and Chico Natural Foods, is very different than the wines of Sauterne.

But winemaker Marco Cappelli, who owns Miraflores Winery in El Dorado County, uses the same fungus, the same grape varieties, and similar methods as the French to make his white dessert wine called Botricelli—and the wine is a dead-ringer for a classic Sauterne. The Botricelli of 2008 smells of pineapple and tastes of honey, apricot, browned butter and caramel. The 2009 is a deeper amber, with similar but more aggressive flavors, and a spicier finish.

Cappelli uses grapes from a small Lake County vineyard. Some years, the Botrytis fungus fails to properly develop, while other years “bunch rot” may occur when the grapes are over-infected, producing a powerful vinegar scent. But cleanly “botrytized” grapes will taste like honey, Cappelli says—a vivid prelude to the golden-hued wine to come.

Robert Mondavi Winery also has a wine called Botrytis, though production of the sauvignon blanc halted in 2002 when the supplying vines were torn out. Mondavi winemaker Rich Arnold says he is now looking for a new and suitable vineyard—but he says finding a site with conditions equal to those of Sauterne may not be possible in the Napa Valley.

“Conditions there are so different than here,” says Arnold. “We really can’t use the same methods that they use in France, and the wines come out differently, too.” Arnold says that a classic French sauterne is smooth and velvety, while a California imitation is “coarser.”

Yet Mondavi’s 2001 Botrytis, still available for sale through the winery’s website, is as sweet as honey, aromatic as a peach grove, and wonderfully complicated by age. Scents and flavors of dried apricots, raisins and caramel emerge from the aromas of citrus peel and tropical fruits. The wine is a knockout, even if it doesn’t quite taste French.

Want Botrytis? Prefer beer? Dogfish Head Craft Brewery, of Milton, Del., makes a grape-infused, 9-percent-alcohol beer called Noble Rot. Available in California, the beer is smooth, creamy and spicy, with a flowery bouquet of stone-fruit scents. Malt and hops are faintly evident, but the beer owes its refined, fruity character to a botrytized batch of Viognier grapes.