Saturday, December 06, 2008

Experimenting with harvest dates

Most winemakers will tell you that the precise date you choose to harvest your grapes has a fundamental effect on the quality of your wine. I don’t really doubt that, but I’m not sure now to reconcile this with the fact that there are quality-minded domaines (say Clos de Tart, Charolpin or Ponsot) which sometimes pick as much as 3 weeks later than other, equally quality-minded, domaines (say DRC, Lambrays or M&P Rion). When I was musing over this prior to harvest I came to only one clear conclusion – I should do an experiment.

And so I set aside one row of my Bourgogne vineyard for an experiment. On seven dates between 21st September 2008 and 17th October 2008 I picked all the grapes from every seventh vine in the experimental row. The objective was to obtain samples that were as representative as possible of the entire row at seven different dates ranging from a very early harvest to a very late harvest.

I was interested in analytical parameters of each sample (notably sugar and yield) but particularly in how harvest date would affect flavours in the finished wine. Hence I fermented the seven samples separately, attempting to maintain identical conditions for each. Since these were micro-vinifications (about 10kg each), and I didn’t want any unnecessary variability, I chaptalised everything to 13% and added cultured yeast for the fermentation and cultured bacteria for the MLF. Oxygen is the enemy of tiny batches so I was keen to bottle these as quickly as possible, which I did yesterday. I now have enough half bottles to do comparative tastings about 10 times in the future, perhaps once per year.

Although I did taste through everything as I was bottling I don’t want to draw any results from that yet, but there is already one conclusion that is hard to avoid:

The later pickings gave significantly lower yields of finished wine.

This result is perhaps not entirely unexpected given that the period was generally dry (with the exception of 4mm of rain on the 3rd October and 15mm of the 16th October), but I do find the magnitude of the drop interesting (almost 30% over the month).