This morning when I checked the must, it was fermenting furiously and the “cap” (the grape skins and stems pushed to the surface as the yeast generate carbon dioxide) was well formed. Although the fermentation chamber temperature was 78° F, the yeast were so happy that the must was 86°, an ideal temperature for extracting maximum color and flavor from the grape skins, which is what makes the wine red. (Fermented off the skins it would be a white wine, since the juice itself has little color.)

Harvest Day +2: 9:30 AM: Fermenting furiously (86° F!), cap well formed

Now it was time to add some yeast food to make sure the marriage continues happily. Yeast who run low on the nitrogenous material they need for reproduction get stressed and may adopt metabolic pathways that generate nasty odors (such as hydrogen sulfide) and flavors. I added 2 grams each of diammonium phosphate (DAP) and Fermaid. The little scale I’m using is accurate to 0.05 grams, an accuracy that a few years back would have cost hundreds of dollars, but now is available for just over $30, thanks to the illegal drug trade. Ain’t capitalism wonderful?

Harvest Day +2, 9:45 AM: Adding DAP and Fermaid (yeast nutrients)

During the day I monitored the temperature and punched down the cap from time to time. By 11 AM, the sugar level had already dropped to just over 20° Brix. We went off to the Quaker Older Folks potluck, and when we came back and I checked it again, at 10:40 PM, it had dropped even more dramatically, to 11.3°. I added 2 more grams each of DAP and Fermaid, and put it to bed for the night.