Ask Wine Wizard

Late Malolactic


Jeff Adas — Via email asks,

I am patiently sitting on a barrel of 2010 Sonoma Zinfandel that still has a bit of a bite. Is it too late to send it into malolactic fermentation (MLF)?

To shed light on your query, the Wine Wiz consulted the Winemaking Magic 8 Ball™ and the answer that floated to the top was, “Outlook not good.” If your 2010 Zinfandel still hasn’t gone through ML fermentation (where malic acid is consumed by lactic acid bacteria, turning it into lactic acid, softening the wine and preventing future ML fermentation in the bottle) it probably won’t. Do I think you can restart your stuck ML fermentation? The short answer (before we get to the long one) is that if you have already added enough SO2 to your wine to be carrying a free SO2 of 10 ppm or above (I recommend a storage FSO2 of at least 25 ppm), it’s very unlikely that you’d be able to restart it as sulfur dioxide is extremely toxic to malolactic bacteria. If you haven’t added SO2 to your 2010 Zinfandel, I’d be amazed if you have anything drinkable left as in the intervening two years it’s probably been attacked by all manner of bacteria, ML or otherwise, Acetobacter being probably the most common infiltrators.
Response by Alison Crowe.