Accidentally introduced film yeast, will carbonating kill it? - Home Brew Forums

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Old 08-03-2012, 12:43 PM   #1
Jun 2012
Washington, DC
Posts: 6

I racked my cider after primary intending to bottle it, when I realized i didn't have enough bottles. My nearest homebrew store is a half hour away and I don't have a car, so it was a couple of days before I could bottle.

When I opened it up to prime, there was film yeast on the top, probably because I left too much headspace since I wasn't intending to let it sit more than a few minutes originally. To be clear, there was far, far, less residue in mine than in the linked picture. I'm talking a millimeter thick or less. Sadly, I had to stir it because it wasn't primed yet, but when I did, the film turned into a golf-ball sized piece of foam that looked exactly like the foam you get when oxygenating beer before bottling. I scooped out as much as I could, but didn't get it all.

After some research, it looks like oxygen deprivation can work to suppress film yeasts. To me, that seems like in theory the CO2 produced while carbonating would be enough to kill the yeast, but then again, there must still be enough oxygen in there for the good yeasts to do their thing and carbonate the beer.

I guess there's not much I can do now, but it would be nice to know whether to expect vinegar or not when I open the first bottle. Does anybody have any experience with this?

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Old 08-03-2012, 08:31 PM   #2
Apr 2009
Posts: 1,018
Liked 59 Times on 56 Posts

Have you added metabisulphite (camden tablets)? Camden tablets will suppress the film yeast. What you say about priming is correct, the yeast will consume any oxygen in the cider, but that takes a week or two and film yeast may form in the meantime. You should be ok but always try to minimise oxygen contact with your cider, oxygen is the enemy.

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Old 08-04-2012, 12:58 AM   #3
Nov 2011
Finger Lakes, NY
Posts: 1,132
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Probably won't be vinegar but it may have some off flavors. gregbathurst is correct, you should add some metabisulphite then bottle as normal. The CO2 will make your cider slightly more acidic and less hospitable to surface yest infection. Not sure as to your plans for the cider but a perfectly dry cider (no 02 or sugar left in the bottle) or a pasteurized cider (see pappers awesome sticky) will also prevent the yeast reforming.

You can save a batch with surface yeast, which is not necessarily an 'infection' in terms of a faulted beverage.
In all the states no door stands wider,
To ask you in to drink hard cider

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Old 08-04-2012, 11:11 AM   #4
Senior Member
Nov 2009
Posts: 219
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I had some film yeast last year. I sulfited and bottled it still. It was delicious. No off flavors.
Sirius Cider

"There are more old drunkards than old doctors." Benjamin Franklin

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