Noble Rot...The Stilton of Wine.
Nobel rot is one of two types of rot that can occur from the fungus Botrytis cinerea. The two forms occur in damp conditions however, the Nobel form happens when the days are dry and sunny. If the weather continues to be wet the fungus forms grey rot which is detrimental to the vine and wine cannot be produced.
Stilton cheese and Nobel rot wines are made by funguses; both are a type of Ascomycota (the largest group of fungi with thousands of different species). The influence of these ‘moulds’ creates characteristic flavours in both and has a great impact on the final product. The fungus, Botrytis cinerea perforates the skins; the holes allow evaporation to occur, hence why dry conditions are needed. This in turn concentrates the sugars, acidity and flavour compounds in the grapes as the amount of water is reduced.
It is rare that whole bunches will all be affected so careful hand picking is required, one of the factors is the bottle price is higher. Another reason for the expense is that producing Nobel rotted wines is risky. The fungus will not occur in some years and in bad years will destroy the grapes with grey rot. The third reason for the high price is yield, due to the grapes being concentrated by evaporation the water content is far lower. This decrease means less liquid can be pressed for the grapes decreasing the amount of wine that is made.
Unlike ice wine the varietal flavours of the grape will be less apparent and instead replaced with typical honey, marmalade, caramel and sometimes even ginger notes. It's important to use grapes with a high acidity otherwise the wines produced will be flabby and unenjoyable.
The intense sweetness means that this isn’t a wine for daily drinking and is more commonly used as a dessert wine or an aperitif. There are a number of names given to bottles that have been produced this way. Tokaji is the common name for these wines in Hungary, Sauternes in France, and Beerenauslese or Trockenbeerenauslese in Germany and Austria. Many other countries also produce these styles of wine and have individual names for them.
Evaporation- The conversion of liquid into a gas, usually water.
Varietal flavours- The flavours found in the grape, specific to the variety.