The production of a Monbazillac rests in the hands of a vital actor: Botrytis cinerea, a microscopic fungus responsible for the famous noble rot.
The grapes are harvested “noble rotten”: the berries are purple, wrinkled, dried and covered with an ash-like white down (thus the name Botrytis cinerea which means ash-like cluster).
However this rot is only “noble” under certain circumstances: the berry has to be completely ripe (around mid-september) and foggy mornings must give way to sunny afternoons.
As the Botrytis cinerea colonizes the grapes, the berries’ appearance changes. “Speckled” berries become “full rotted” and eventually “roasted”.
"FULL ROTTED" STAGE:
The contaminated berries are dotted by branching tree-like brown spots (conida). Botrytis cinerea therefor develops under the skin giving the berries a purple-brown colour. At this point the berries’ weight has not changed.
The hot and sunny afternoons bring about an evaporation of water through the skins made permeable by Botrytis cinerea’s enzymes. This evaporation of water causes the concentration of sugar to increase and gives the berries a wrinkled, candied appearance with a purple-brown colour (like a raisin).
In addition Botrytis cinerea colonizes clusters heterogeneously. Therefore a single cluster may present all of the different stages of the fungus’ evolution: speckled, full rotted and roasted.
This reality forces the harvest to take place by hand and in various passes (every one to two weeks). This allows KALIAN to harvest only the portions of the cluster that are affected by the fungus.