Of course the call came at perhaps the worst possible time. Lisa and I were set to leave town for four days and so I couldn't really start a ferment. The solution turned out to be a well known technique known as cold settling.
We ended up with about 90# of grapes. Field testing showed pH 2.81 and SG of 1.086. We whole-cluster pressed around 6 gallons which tested at 2.85 and 1.084.
Before heading out of town, I raised the pH to about 3.0 with 2T calcium carbonate, added 2T pectic enzyme, then capped the bucket for a 4 day period of cold settling in the fridge.
The wine 4 days later had dropped a fair amount of tartaric acid and sediment, and racking yielded a nice clear must. I will definitely perform cold settling again! The pH hung in there at 2.99 but the TA was brutally high at 15g/L. Calculations indicated that 7T of calcium carbonate should drop the TA to around 8g/L and coincidentally this was the maximum recommended dose. We slowly added the calcium carbonate, watching the pH, but eventually wound up adding the maximum amount and arrived at an acceptable preferment pH of 3.33.
We used 11g Opti White, 6g Booster Blanc, 0.6g Lallzyme EX. We used QA 23 with GoFerm and Fermaid K, step fed. We mostly succeeded in keeping the fermentation below 15C using ice packs placed in water every 4-6 hours in the outer bucket.
The cooler temps didn't slow down QA 23 at all. Bentonite was added at day 3. The Vignoles dropped to 1.004 by the 7th day with great aroma and no off odors. After racking, we are just short of 6 gallons.
We'll give it a few days to finish up in the carboy and rack it off to a 5g and 1/2g carboys. A very promising wine!
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