Ask Wine Wizard

Malolactic Fermentation After Cold Stabilizing


Jim Boutin — Pownal, Vermont asks,

Recently I conducted a paper chromatography test to check the status of malolactic fermentation introduced this fall into a number of 5-gallon (19-L) Marquette carboys produced from my backyard vineyard. Results showed plenty of malic acid still present. I plan to cold stabilize over the winter months in my winery. Will malolactic fermentation under these circumstances naturally kick back in when temperatures rise in the winery in the spring? Or is it best to re-inoculate with new culture and nutrients in the spring?


I always think it’s wonderful when people can do a “natural” cold stabilization over the winter months. It’s an incredibly intuitive and very old-fashioned, non-interventionist way to accomplish a key winemaking task. It never gets cold enough here in Napa, California during the winter to really knock down any significant amount of our tartrate crystals (the goal of cold stabilizing a wine), so that’s very cool (LOL) if you can do it. I do indeed think that it’s very likely that your malolactic fermentation will re-start once the weather warms up.

Instead of re-inoculating (malolactic bacteria are expensive!) you could wait and see if you start to get any activity when the temperatures start to rise. You can do this by monitoring the disappearance of the malic acid spot on your paper chromatography test. In addition, you can also listen at the mouth of your carboys for the little “tick . . . tick . . . tick” of carbon dioxide bubbles being produced by an active malolactic fermentation.

To be sure that you’re detecting any change, do a chromatography measurement right before you put your wines out in the cold to start stabilizing. On your paper, since the spots will fade over time as the solvent degrades, very carefully (don’t touch the paper with your hands, use gloves as the solvent is toxic) draw a pencil line around the little malic blob. This way when you test again in the springtime months, or whenever you believe malolactic fermentation has resumed, you’ll be able to see if the size of your spot has shrunk and if activity has indeed kicked back into gear.

If you don’t see any signs of activity after the weather has been warm (above 55 °F/13 °C) for a few weeks, and if you’ve tried things like bringing your carboys inside or wrapped them with electric blankets, then it’s time to consider re-inoculating. Make sure that the alcohol isn’t too high (>14.5% is inhibitory), the pH too low (<3.3 is inhibitory), or the temperature too low (>55 °F/13 °C is ideal).

I’m so glad that you mention malolactic nutrients! So many people just toss in a bunch of bacteria and hope for the best, not realizing that malolactic bacteria are even more fastidious in their nutritional needs than yeast cells are. Especially since the wine has been sitting for a while, it’s possible that many things have fallen to the bottom of the vessel or have been consumed (albeit slowly) over the winter’s nap and are now unavailable. Re-supplementing with a nutrient at this time is key.

Additionally, be sure not to add any SO2 as malolactic bacteria are extremely sensitive to sulfur dioxide. Hold that addition until you have confirmed completion. Good luck with your cold stability, and I hope that your wine does reignite its malolactic fermentation in the spring. If not, re-inoculating is nothing to be ashamed about!

Response by Alison Crowe.