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White Film In My Wine Barrel

TroubleShooting

Pete Russo — Newberg, Oregon asks,
Q

I have a new 26-gallon (100-L) Hungarian oak barrel full of Merlot wine. When I went to top it off this month, I found a thick white film on top of the wine. It was so thick that it stuck to the wine thief when I took a sample to test for pH. The wine still smells and tastes OK. I have been making wine for 10 years and I have never seen this before. I added some SO2, over-filled the barrel until I didn’t see any more of the “white stuff” come out and put the bung back in. Is this something I should really be worried about? And is there anything else I should be doing?

A
It sounds like you are doing the right thing. This is probably an aerophilic “flor” type yeast that is eating alcohol, and in the presence of air (if it was slightly untopped) decided to have a little fun in the headspace. If you don’t feel the taste or aroma are really damaged or changed, completely topping, plus adding a little bit of extra sulfur dioxide should do it. I would keep an eye on the headspace in the barrel, however. Do you possibly have a leak in the barrel? Is the bunghole forming a tight seal with the bung? Sometimes bungs can harden with time and, due to lack of elasticity, form an imperfect seal. Did you check the pH? If it’s much over 3.60 your SO2 will have a hard time being effective even if you did add a little bit more. If you suspect you might have a higher pH I would perhaps add 0.5 g/L tartaric acid and stir in gently without oxygenating. Definitely keep the sulfur dioxide at least 15 ppm higher than you normally do,
Response by Alison Crowe.