Potassium Bicarbonate & Cold Stabilization

[Cole]

Hi, all

I have a question regarding wine de-acidification using potassium bicarbonate, and the need for subsequent cold stabilization.

Some details; question further down:

I was asked by a relative to make a wine using Clinton grapes he had been growing in his backyard for some time. This is no longer a typical dry red wine making grape, but I decided to give it a try.

I crushed to approximately 4 gallons / 15 litres of must, added 3 pounds of sugar, and while the pH was quite low (around 2.7) pitched Lalvin RC212 to ferment on the skins. Fermentation completed well, but after pressing, the resulting wine was obviously still very acidic. I do not have the materials to test acids at this time, so I am forced to calculate using pH and estimate acid content.

I decided to put this wine through malolactic fermentation, which required bringing the pH up as not to inhibit the bacteria’s performance. This was done using 10 grams of potassium bicarbonate, a conservative maximum dosage for my batch size.

I pitched the bacteria I use for other reds, Lalvin VP41. After three days, the bacteria seem to be doing their thing. Following malolactic fermentation, I intend to adjust the pH up further with water (I wanted to see where fermentation and malo brought the pH before diluting [In retrospect, I could have added water to the must, increased the sugar, and performed a double salt de-acidification prior to fermentation]).

Question:

My question is related to cold stabilization and its impact to the wine’s pH above/below the 3.65 threshold; I am expecting this wine still to be somewhat acidic at the end of malolactic fermentation, and am concerned that cold stabilization will further increase acidity because its pH will be below 3.65. At the same time, I’ve read it’s “necessary” to cold stabilize following the addition of potassium bicarbonate.

1.) Is the cold stabilization rule of acidification below a pH of 3.65 applicable when potassium bicarbonate + cold stabilization are used?

I have read that approximately 75% of the de-acidification from potassium bicarbonate is completed without cold stabilization. Whether or not this is accurate:

2.) Is a wine safe and palatable when potassium bicarbonate is used without cold stabilization?

I will be filtering this wine through a 5 micron pad, though I’m not sure this makes a difference (I also have the ability to filter up to 0.5 microns).

I appreciate any help you may be able to lend. This forum has been a great resource for me in starting out in wine making.

Thanks!

Cole

 

[winemaker81]

Cold stabilization is a temperature based reaction -- wine can support a certain amount of tartaric acid in suspension, which varies according to temperature. By reducing the temperature to 32-40 F and keeping it there a week or 2, the amount of acid the wine can keep in suspension lowers. The result is the excess acid forms crystals and drops out of suspension. Make sure you rack before letting the wine warm up, else some of the crystals may dissolve.

Regarding K-bicarbonate, AFAIK it interacts with acid to neutralize it, a chemical reaction. I've never heard of having to cold stabilize in conjunction.