My last several posts detailed the harvest and initial winemaking steps for Three Fox Vineyard's Viognier and Pinot Grigio. As I mentioned, those grapes were harvested and fermentation initiated on September 7th. On September 8th, we received a load of Vidal Blanc grapes from a local grower for our "Appassionata" off-dry Vidal and started that in on fermentation. On September 13th, we took some Brix readings (the level of sugar - read my recent post for more info) to see how our fermenting wine was coming along. Here's what we found:
Brix at Harvest (9/7) = 23.7
Brix on 9/13 = 9.0
Brix at Harvest (9/7) = 24.9
Brix on 9/13 = 9.2
Brix at Harvest (9/8) = 24.0
Brix on 9/13 = 10.0
The fermentation reaction takes the sugar from the grape juice and converts it into alcohol and carbon dioxide. [The generic chemical reaction for a fermentation reaction is C6H12O6 → 2C2H5OH + 2CO2 + 2 ATP, or in English: glucose (sugar) → 2 units of alcohol + 2 units of carbon dioxide + 2 units of energy (which is why the yeast are even bothering with this in the first place) ] So, as you can see after not quite one week our fermenting juice is well on the way to fermenting to dry wine (i.e., Brix is roughly zero, meaning there is no residual sugar left in the wine). Cool, eh?
Next post: First up for harvest for the reds is the Chambourcin grape. Reds undergo a slightly different process than the whites, as reds are fermented with all of the skins and seeds - not just the juice as is the case with the whites. More on that soon!