hmm infected beer, not the usual question though.

[Svecke]

Hello, Im a homebrewer from sweden and Ive brewed for a couple of years. I work as a microbiologist and I have tested most of my beers for infections and they have al come up clean. Except for my last 3 beers which have been infected with from what my first analysis is some kind enterobacteriaceae (not e.coli, tested for that) and one of them even Bacillus Cereus.

These three beers are all dry hopped in the keg and they are the only ones Ive done that with. The pH is in the normal range and they are in the range of 6-7 ABV (modus and pliney clone). Got the fermantation going in about 5 hours with No funky smells during fermantation.

Both bacteria are found on plants and im suspecting the hops even if it has the antibacterial effect. Im going to do some more tests, let it sit and see if it grows even more ore dies off and im going to test my hops.

We emptied one of the kegs this weekend and no one got sick or anything but I belived it got some kind of sweet off flavor.

Anyone else have any experience with this?

/Svecke

 

[Yooper]

If you sampled before kegging, and then after, that would be helpful.

If you did not, and the sample is after kegging, it could be before kegging (the siphoning tubing or secondary), or during, or after. The keg can hold lots of microflora, from in the diptubes and o-rings, to the poppits, or the lines or taps.

The hops are the most unlikely contaminant.

The posts and poppits and tubing are the most likely.

 

[Svecke]

I thought about that it could be something in the keg. but I did some more tests, this time on pure hops, pellets and cones and re-tested the beer. both the hops were positive for EB and Basillus cereus but the beer was now clean. So the beer seems to have killed the bacteria but im pretty sure it was the hops that introduced it. however if I would have tested it a couple of days later it may have not showed anything at all.

 

[Qhrumphf]

I would assume that hops are much like honey, in that anti-microbial does not mean sterile- bacteria will be present but in small numbers and not able to flourish. I know that brewers dry hopping with wet hops have picked up infections from it, even with pellets I would expect something to pop up (and had a brewer telling me as such a few weeks ago- their microbiologist picks up random stuff in their dry hopped beers all the time at low levels).

So I'd say you're probably correct, the organisms came from the hops, and then the pH and alcohol in the beer (plus the hops) killed it off.

Of course, I'm NOT a microbiologist so take my 2c with a grain of salt.

 

[Svecke]

yep my thoughts too