Stubborn White Film Mold

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Nov 2, 2020
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I've been making wine for about 4-5 years both in carboys and quarter barrels. I've had issues with white film mold at the top of my carboys in the past - but have been successful in handling it with careful removal (float it out) and a good clean of the carboy neck area (inside and out) and sanitization of the carboy stopper and air gap. I've also tested the free SO2 and I'm in the 30-40 ppm range. However - this year I'm struggling with this issue and can't seem to get it resolved on one or two of my 8 wines. Thought I would throw it out there and see if anyone has any other remedies that I could try? Nothing unique with either of these wines - a couple of red wines (from grapes) - a nice Barbera and a red blend with Zin and Petite Syrah. Appreciate any suggestions.
It sounds like you're keeping things clean. I presume your transfer hoses are being sanitized too. I think your SO2 levels might be too low to prevent the mold. I understand wanting to minimize SO2, but you need to have enough to protect the wine against this very thing. If it was me, I'd add a larger dose of SO2 to get to about 80ppm. (However, This dosage will probably stop MLF). I've heard from experts that with SO2 one larger dose is more effective than several smaller doses. Also, as the wine ages and particles fall to the bottom, the SO2 levels will decrease. Sterile filtration might work, but for home winemakers that's pretty hard (and expensive) to accomplish.
Sounds like it could be Mycoderma or "flowers of wine"but hard to tell w/o a pic. Mycoderma is a yeast. A yeast needs substrate to grow in plus Oxygen. If you are 100% sure your free SO2 levels are that high I would make sure you are fully topped up n your carboy (2" max air) spray the top of the wine with some of your KMETA sanitizing solution. Let it sit on top. Then stopper the wine with a solid stopper and see if that stops the film from reforming. You may need to reopen, wipe the film away with a paper towell and then reapply more KMETA and re-stopper but a lack of O2 will knock it out but you will have to stay on top of it.
What yeast did you use with your wine? Check out this thread also~ Some bio films are not as sulfite sensitive although most are. Sparging the headspace with nitrogen or argon could be helpful as well. Also, bringing the temperature down and out of the growth range... I may have my wife convinced to build a wine cellar / fruit cellar.....
Agree with what's been said above. Also double check your pH. 30-40ppm should be sufficient, given your pH is in a good range. If you're sitting at 3.7, 3.8 or higher, you need more sulfite, though it sounds like you have a surface issue (likely mycoderma, as was noted). As Mike noted, when I've had that issue, I double check sulfite and pH, make sure the carboy is topped up, spray some SO2 solution in the top of the carboy and put a solid stopper on it (assuming I'm comfortable that it has degassed).
Thanks for the input. And yes - its that basic whitish yeast film (that I call mold). Headspace is always minimal - about an inch below the stopper. PH is good on the wine in the 3.5-3.6 range. The oxygen exposure could be a culprit as some of my stoppers are getting older and may not be sealing as well. I tried some silicone stoppers this year and can't decide if I like them more than the rubber/latex. I'll also try leaving a bit of my SO2 closer to the surface instead of stirring in. I still haven't picked up a tank of argon or wine mix gas setup as I haven't been able to justify the cost of the rig. But maybe it's time to start looking. Maybe I can find one one the used market for a reasonable price. Thanks for the tips.

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