Ask Wine Wizard

Achieving Cold Stable Wines

TroubleShooting

Don Catharine — Burnt Hills, New York asks,
Q

In your article “Malolactic Fermentation After Cold Stabilizing” https://winemakermag.com/wine-wizard/malolactic-fermentation-after-cold-stabilizing you mention that malolactic fermentation (MLF) may start back up after cold stabilizing when the wine warms back up.

For me, as in your article, MLF was underway albeit somewhat slowly; I believe because the pH of the different wines was running low, ~3.2–3.3 and ~11% ABV. I didn’t want to miss the window of cold nights in my upstate New York garage, so mid-February I placed the carboys out in the garage. After One month I brought them back inside. The next day I performed a chromatography test to verify MLF was not complete. I then added 1⁄2 the recommended dose of Opti-Malo Plus and stirred it in gently. I did not rack the wine because I was concerned about subjecting the wine and MLF bacteria to oxygen.

• Should I have racked the wine?
• Should I be concerned that some of the tartrate crystals that have fallen out will be mixed back into the wine or will they remain as crystals never to become part of the solution again?
• How concerned should I be about subjecting the MLF bacteria to atmosphere? I can purge the carboys with CO2 if you think that would help.

A
For those readers who are not familiar with the article referenced, I talk about how it was likely a reader’s malolactic fermentation would pick back up again when the weather warmed up again in the spring (he wanted to over-winter his wine undergoing MLF outside in order to help it get cold stable). It sounds like you also decided to take advantage of a cold spell in an attempt to get your wine cold stable and are hoping your malolactic fermentation will reignite now that you’ve brought it inside . . . and you have a few questions about cold stability in addition. I like that you’ve added some ML bacteria nutrients (Opti-Malo Plus is a good choice), which are especially important as ML bacteria are notoriously fastidious, in that to fully function they have very specific nutritional needs. A little background on cold stability: Grape juice naturally contains tartaric acid and potassium, which can combine to form a salt called potassium hydrogen tartrate. Also known as KHT, potassium bitartrate, or cream of tartar. This salt can exist in a
Response by Alison Crowe.