In making Sauternes, the great sweet white wine of Bordeaux, the mold that helps concentrate the grapes is gently washed off before the grapes are fermented.
The furry gray mold-covered grapes that make Sauternes may look like miniature mice, but that Botrytis cinerea mold (also known as pourriture noble or noble rot) is not washed off or in any other way removed before fermentation. In fact, it contributes to a Sauternes’ flavor—and not in a way that seems like something left too long in the back of the refrigerator. Botrytis adds an extra dimension, sometimes described as being faintly like sweet corn or mushrooms, to the overall complexity of the wines. The influence of Botrytis actually begins in the vineyard, as the beneficial mold punctures the grapes’ skins in search of water to germinate its spores, the water begins to evaporate and the grapes dehydrate. Inside the shriveled berries, the sugar in the juice becomes progressively more concentrated. The botrytis also alters the structure of the grapes’ acids, but the amount of acidity in the wine is not diminished—of crucial importance to balance the heightened sweetness in the finished wine.