October 4, 2015

The nobility of botrytis

The secret of the Sweet Bordeaux lies in the existence of a small fungus, the botrytis cinerea, which the famous noble rot originates from. Under its action, the grapes develop aromas that give uniqueness to the sweet and sugary white wines of Bordeaux.

Unique climatic conditions

The Botrytis cinerea is a common fungus in the wine world, it is also often considered a pest. In the Sweet Bordeaux production zone and especially in the South Gironde, the botrytis is however sought after. In this geographical area, botrytis installation takes place in very specific climatic conditions. Olivier Fargues, vineyard manager at Château La Bouade explains, “the Ciron, a river that is born in the Landes, has colder waters than the Garonne. In September and October, when the two waters meet, it often creates fog in the valley. That morning humidity favors the uniform installation of fungus. During the day, the wind and the sun effectively dry the grapes“.

The explosion of flavors

Between sun and humidity, the botrytis settles generally in mid-September on the grapes. Instead of destroying the bunch, the fungus micro-perforates the skin of the berry and makes it porous. It is at that moment that the action of the botrytis becomes interesting for the Sweet Bordeaux. Olivier Fargues says, “attacked, the plant defends itself. Its antibodies produce precursors of aromas and flavors, in addition to those already present in the grapes“. The grape berries go from golden yellow to purplish pink. It is at that time that the berry defends itself the most, so that’s when most of aroma precursors develop. In parallel, the micro-perforations in grape skins allow water to evaporate and the flavors concentrate in the fruit.

Choosing the right time for the harvest

To trigger the harvest, the art of the Sweet Bordeaux winemaker is to identify the moment when the grapes reach their optimal point of dehydration. “We wait until the water evaporates to achieve similar as currants“, continues Olivier Fargues, “in the classic years we begin to harvest in late September / early October and we finish in late October or early November“. This year, Château La Bouade begins its harvest at the beginning of this week: “for the launch, we rely on very visual indications. We walk in the vineyards to determine the order in which we will start picking. I waited, because for me the grapes were not concentrated enough. This week, I will do a very nice first sorting“, concludes Olivier Fargues.