Q: Last year I made a rosé from Marquette. At the time of fermentation, the juice was pH 3.33 and TA 10.0 g/L. I decided to ferment the juice even though the acid was a little high. After fermentation, the color of the rosé was great and very clear. The nose was a beautiful strawberry. Unfortunately, the wine was too crisp because the acid was too high. I decided to reduce the acidity with potassium bicarbonate. I conducted some bench trials and decided to use half of what I thought would be the right amount. The addition was conducted and the wine became cloudy. This was fixed by using Sparkolloid. In preparation for this fall, I am assuming the Marquette juice will still have a higher titratable acidity (TA) than I want. I want to shoot for a TA around 7.0 g/L or less and would prefer to do as little as possible to the wine after fermentation. Does it make sense to test the juice and adjust the acidity of the juice prior to fermentation? Do you still recommend potassium bicarbonate to decrease the acidity? Finally, do you recommend I cold stabilize the rosé prior to bottling?
— Bill Thompson • Andover, Minnesota

A: That’s great that you are already planning ahead for this upcoming harvest. Indeed, a TA of 10.0 g/L is very high and I would certainly plan on de-acidifying for style as well as to facilitate fermentation. As with just about any major adjustment you’ll make to a wine, the earlier you do it the better. If you can’t do it in the grape phase (which Mother Nature really controls) definitely do it in the juice phase. Be careful if you use calcium carbonate, which can cause a calcium tartrate instability. Since you’re probably only going to be taking the TA down by 2-3 g/L I would say go ahead and use potassium bicarbonate again.

De-acidifying wine is a multi-step process with many things to be taken into account. One of the best articles I’ve read about the details and chemistry behind the procedure was written by my friend Dr. Jim Harbertson at Washington State University. He offers a great rundown with links to handy additive calculators in his article “Managing High Acidity in Grape Must and Wine” (http://wine.wsu.edu/research-extension/2010/10/managing-high-acidity/).

Rosé wines can be tricky and I do not recommend you let the wine go through malolactic fermentation. I tried this one year on a pink wine and found that it lost quite a lot of its color and turned orange. Don’t forget that reducing acidity will also tend to shift color from the red/blue hues to orange-ish. Many of my winemaking friends have similar cautions about letting rosé wines go through malolactic fermentation. I do certainly suggest you try to do some kind of cold stabilization prior to bottle to reduce or eliminate potassium bitartrate crystal precipitation.