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-   -   Airborne wild yeast (http://www.homebrewtalk.com/f11/airborne-wild-yeast-228839/)

conpewter 02-28-2011 11:20 PM

Airborne wild yeast
Hey all, I've been brewing for a few years now and the batches over the past year have all ended up with some sort of wild yeast issue. One of the problems is that it doesn't really show up until a couple months after brewing.. yay.

I just put my oatmeal stout in a keg and I tasted some of the beer out of the fermenter (put some in a glass during siphon) and I can once again detect a bit of the infection, we'll see if it shows up stronger later.

My last thought since I've eliminated so many variables is that I have a sort of house yeast that is present in the air/dust in the house. Now that I've had so many infected batches I would think it is possible. Has anyone else ran in to this?

theredben 03-01-2011 01:29 AM

Why do you suspect wild yeast? Plating?

conpewter 03-01-2011 12:25 PM

I suspect a wild yeast issue due to an off flavor I get start getting after a month or so of the beer being finished. Also when I've done bottling every bottle becomes overcarbonated. It doesn't turn sour or tart, just off, some people have described it as apple.

conpewter 03-01-2011 12:26 PM

The kegs also became overcarbonated after sitting for a while outside the fridge.

theredben 03-01-2011 11:52 PM

Why yeast though? As opposed to bacteria.

conpewter 03-02-2011 01:13 AM

Not really sure it matters which, but I suspect a wild yeast because the beer doesn't taste bad, just off, and the speed of the infection, bacteria seem to work faster than that. Either way I want it to stay out of my brews.

theredben 03-02-2011 02:17 AM

Are you washing yeast? You would not expect that much airborne yeast this time of year unless you are doing other things (baking,microbiology lab) in your free time.

Can you describe the off-flavour? How about your standard sanitation procedure?

kiki374 03-02-2011 02:26 AM

It happens sometimes with cheese making and it's called phage. They recommend changing cultures periodically and, of course, keeping equipment scrupulously clean.
Maybe you could try changing your usual yeast and only using boiled water.
Hope this helps.

theredben 03-02-2011 03:00 AM

The difference with brewing is that we are talking about yeasts, which are much more seasonal than bacteria. That is why I was wondering if the OP is washing yeast. If not, then I highly doubt recurring wild yeast. I am no cheese-maker, but "killer" bacteria sound much different than the slow, insidious growth of wild yeast in beer.

EDIT: Reading more about bacteriophage, I sure am glad we don't have viruses in beer! Sanitation would be a nightmare!

conpewter 03-02-2011 01:55 PM

I do all of my brewing indoors, so I don't think the season would have anything to do with it. Since I've been having the issue I've been using brand new packs of S-05 yeast instead of any of the washed yeast. So about a year of using new yeast now.

I've been using star-san for sanitizing. I switched to no-chill as a way to try to get around this problem, but before that I had a CFC I would pump boiling wort through for the last 10 minutes to sanitize.

Kegs/bottles are cleaned with an oxyclean soak before being sanitized with star-san and in the case of the kegs, stored with some star-san in them.

We were making yogurt upstairs, but I tried to keep that separate from the brewing. I've never done a lambic. I have had infected beers spew out when opening them (near the brewery). I also do all my bottle cleaning in the same room as the brewery. Grains are stored and milled in a separate room.

The brew that is in the chest freezer now has yeast from a local brewery. I am wondering if the chest freezer has a mold issue (though I try to keep some desiccant in there) and when I put ~70 degree wort in there, and drop it to 64 I get some suckback... maybe pulling in some infection.

Thanks for any help you guys can provide... I gotta kick this thing or quit brewing :(

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