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Fungus Creates a Sweet Bottle of Wine

St. Paul, Minn. (November 10, 2005)—Growers of plants and vegetables typically perceive plant disease and mold as a negative occurrence, but for some winemakers, the fungus Botrytis cinerea is a welcome and “noble” rot.

“Botrytis can be a good guy or a bad guy,” said Wayne Wilcox, plant pathology professor, Department of Plant Pathology, Cornell University, Geneva, NY. “When Botrytis is a bad guy it produces gray, fuzzy mold that covers and destroys the quality of fruits and vegetables,” said Wilcox.

“When Botrytis is a good guy, it will slowly rot grapes while they are ripening causing them to shrivel and dehydrate, which concentrates both the flavor and the sugars,” Wilcox said.

Winemakers refer to this process as a ‘Noble Rot.’ The end result is a uniquely flavored type of wine called botrytised wine. Known for its honey color and sweet taste, botrytis wine is typically served as a dessert wine or as an accompaniment to sharply-flavored ripe cheeses.

Botrytis occurs naturally in numerous wine-growing areas, but is most common in places that receive rainfall during the preharvest period. The most famous region for botrytised wine is the Bordeaux region in France where the wine is known as Sauternes. Botrytised wine is also naturally produced in Germany, Hungary (where it is known as Tokaj), eastern North America, and occasionally in Chile and Australia.

In dry climates such as California and much of Australia, where Botrytis does not usually occur, some winemakers will inoculate their harvested grapes with the fungus in a controlled environment. “While this is a very labor intensive process, the winemakers are able to create a delicious dessert wine by introducing this fungus to their grapes,” Wilcox said.

The American Phytopathological Society (APS) is a nonprofit, professional scientific organization. The research of the organization’s 5,000 worldwide members advances the understanding of the science of plant pathology and its application to plant health.