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Dealing With Acid Issue on a Raspberry Wine

TroubleShooting

Jeff Davis — Mount Pleasant, South Carolina asks,
Q

 

I need help in solving a riddle with a high titratable acidity (TA) and medium-high pH raspberry wine. I am aging This raspberry wine currently and the TA, post- fermentation is about 13.4 while the pH is 3.6. That seems pretty far out of line with what normal wine specs are and I’m not sure how to deal with it. Also of note, I added some calcium carbonate and the pH/TA balance didn’t react like I expected it would. What do you recommend for continuing treating/aging of this wine?

Here’s an outline of what I did (edited for length): Prior to fermentation, I added the calcium carbonate and after two hours racked into a fermentation bucket. I took a sample and measured the following specs: pH 3.54, TA 11.5, Brix 22.

It looked like the calcium carbonate had worked. I Started primary fermentation using Lalvin 71b and added yeast nutrient. After primary fermentation ended, I racked the wine off the lees into a 6-gallon (23-L) carboy: pH 3.6, TA 13.25 (??) how did it go up?

One week later I racked again: pH 3.6, TA 13.5. I proceeded to degas the wine and added ¼ tsp. of potassium metabisulfite powder and finally placed in a refrigerator to cold stabilize.

So how would The Wine Wizard proceed from here?

A
I really applaud you for keeping such detailed records and testing regularly. This really helps me when diagnosing issues and coming up with ways to help. I want to start off by saying that raspberries are a really high-acid fruit and that high titratable acidity won’t necessarily track with the pH like it does in wine from grapes. For background (and to add to the fun of fruit winemaking), there can also be a considerable swing in pH/acidity and Brix depending on raspberry cultivar and growing season. In a study of four varieties in the 1980s and 1990s, a TA swing between 1.5% to 2.64% was observed. Buffering capacities for fruits will be different and we can’t expect a raspberry wine to behave like a grape wine, especially when the inherent chemistries are so different. Grapes are high in tartaric and malic acids especially, with smaller amounts of citric and other acids. Raspberries don’t have tartaric or malic acids and are very high in citric and ascorbic acid. In short, deacidification rules and practices that we may be used to
Response by Alison Crowe.