Some of the world’s best dessert wines get their distinctive character from a particular grape variety. Others result from an unusual winemaking process. Sauternes wine can’t be replicated anywhere, because its tremendous quality results from the place itself.
The Sauternes AOC lies on the bank of the Ciron River in Bordeaux. Mist coming off the cool water consistently engulfs the vineyards in Autumn mists from early evening through the morning or beyond. This encourages botrytis cinerea (aka Noble Rot) to grow on the grape bunches.
The primary grape variety of Sauternes wine is Semillon, which is a particularly friendly host for botrytis. The other two grapes, Sauvignon Blanc and Muscadelle, get botrytis too, though to a lesser extent. Sauvignon Blanc, the chief blending partner, brings zippy acidity and vibrant fruit.
The best sites in Sauternes are on hillsides. There, the vineyards see the necessary fog, but the mist burns off enough that there’s plenty of sun to allow excellent ripening of the grapes as well. The slopes also mean better draining soils which help both ripening and clarity of flavor.
The exclusivity of Sauternes wine comes from the location, but is amplified by the risks in producing botrytis wine and the extended barrel-aging the wines are required to see. To get a high-percentage of botrytised grapes, the harvest must come late in the season. That brings the danger of rain which would require even more extensive sorting. The late harvest also means the grapes are more dehydrated, so the volume of liquid each bunch yields is quite low. Yet the best of Sauternes wines usually come from those producers who dare pick the latest.
After careful sorting at the winery, the grape bunches are pressed and the juice is fermented. The high sugar content in the grapes results in robust alcohol levels, often about 14%. The botrytis not only dehydrates the grapes and brings its own, delightful flavor, but increases the concentration of tartaric acid and glycerol. The former is important for great balance in these sweet Sauternes wines. The latter gives them a thick, satisfying mouthfeel.
When fermentation is complete, the wine goes into French oak barrels. The wine will spend at least 18 months in barrel and a portion of the wood is new. The highest quality Sauternes wine ages longer, up to 36 months, and the percentage of new oak is high.