Paul Cluver Noble Late Harvest Riesling
As you know, it is due to Botrytis cinerea that we are able to make Noble Late Harvest Riesling at Paul Cluver. This fungal growth is initiated by rain during the ripening phase of the grapes. For the fungus to develop further, cool weather and relatively high humidity is required.
However, if the humidity stays high or if it is wet for a prolonged period, a secondary infection of Acetobacter aceti may occur resulting in ‘sour rot’ rather than ‘noble rot’. Generally there is always a measure of sour rot between the noble rot grapes. Measures are taken to limit the levels of sour rot which adds cost to the vineyard management process.
Since grapes infected with sour rot are of no use to us, the selection process during harvesting is of utmost importance. Bunch sorting is critical and the same vineyard is harvested 3 to 4 times.
In order to fufrther ensure that sour rot infected grapes do not make it to the final selection, a berry sorting process is undertaken at the cellar with each of these steps making the wine making process more laborious and costly.
With a varietal like Sauvignon blanc, we anticipate a production of 7 tons/ha. This results in a final recovery of 625 to 650 litres per ton which in turn results in 5800 to 6000 bottles (750 ml) per hectare.
Our other Rieslings delivers between 6.5 and 8 tons/ha – whereas botrytis infected Riesling only delivers 4 tons/ha. We lose an average 2.5 – 4 tons of grapes due to the dehydration caused by the fungus each season.
In the production of Noble Late Harvest wine we only recover 300 – 350 litres per ton – again due to the dehydrated berries. Net result is the equivalent of 1600 – 1800 bottles (750 ml).