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Trying to Work With Grape Juice That is Amiss

TroubleShooting

John Regina — Vernon, Connecticut asks,
Q

I have a Petite Sirah in secondary with the following characteristics:

  • 23 L (6 gal.) of juice (2020 vintage) from the same supplier as I have used for 6 years
  • Source of juice is California
  • Brix: 21.1 (lowest I have ever had)
  • pH: 4.1 (highest I have ever had)
  • Titratable Acidity (TA): 2.5 g/L
  • Free SO2: about 40 mg/L
  • Temperature: 71 °F (22 °C)

I adjusted the TA by adding tartaric acid and achieved a TA of 7.5 g/L with a pH of 3.2. I added yeast (BM45) with nutrient. Fermentation proceeded normally. On day 7 when Brix was 2 I added the malolactic bacteria. On day 9, when Brix was 0.7 I racked the wine off the gross lees. A slow fermentation continued for the next 14 days. I did not take any measurements during this time. But on day 24 I did measure the following:

  • Brix: 0.0
  • pH: 3.2
  • TA: >10 g/L (probably 12)
  • Malolactic fermentation (MLF) is not completed

I didn’t measure FSO2 as the wine had only been racked once up to this time and had always been topped off. I racked the wine off the fine lees and that is where it sits today. The wine tastes very tart but there isn’t any noticeable odor. Apparently, what I thought was the slow tail end of fermentation was actually CO2 forming. Can you please advise me on any steps that I can take to salvage this wine? And what’s your best guess on how this came about in the first place?

A
Well, your grape or juice source really put you in a bind. Those are some of the most unbalanced initial numbers I’ve ever seen, and I would seriously consider getting your juice from another source next year. Numbers like that — with the acid being so low and the Brix simultaneously being low may be, I hate to say, indicative of dilution with water. I really hate to propose that someone would be that unscrupulous and certainly don’t want to get anyone in trouble, but you’d expect a 4.1 pH for a red grape to correspond to Brixes being at least above 25 if not closer to 28. Like I said — whatever the cause, those are very unusual, unbalanced numbers and certainly didn’t give your project much of a starting chance. You did the right thing by trying to add acid to make up for that dangerously high pH of 4.1. Targeting a TA of 7 isn’t a bad thought, though it’s a little high for my tastes and because of the buffering capacity of your juice, landed you
Response by Alison Crowe.