Fun times with infections (guess the bug)

[Befuddler]

After rushing the bottle sanitation on my most recent batch, I've ended up with a lovely case of something nasty. This has only affected a few of the bottles and the rest of the batch is tasting damn fine, so I'm posting this more out of curiosity than rage, and because the infection doesn't seem to be anything I'm familiar with. Here are the money shots:

A classic scaly white pellicle in the bottle. I'm guessing this is an aerobic infection, because I poured half this bottle out then left it a few days to see how it developed. The half bottle has progressed much further than the full ones:


An attempt to focus down the neck of the bottle ends in failure:


The beer pours hazy and headless:


With lovely white lumps in it:


Looks fairly typical, right? Well, there are no acidic, vinegary or sour aromas or tastes present, which has left me somewhat confused. The aroma is hard to pick out because this is a heavily hopped beer, but there's a hint of rubber about it. The flavour is all rubber, with a bit of hoppiness in the middle, then an acrid, ashen, gobful of nastiness at the back of the palate. It's a bit like you've just swallowed an ashtray full of hops actually. It's also very dry and getting drier by the day.

Any ideas what this might be, purely for research purposes, and so I know what I'm dealing with if I get this rubbery mess again?

[orlando]

I have heard autolysis described as "rubbery" but the floaty things suggest a bacterial infection. As you say most are OK the latter is most likely but what........?

[greenxpaddy]

Wild yeast?

Guess it won't be very flocculating but be very good at getting a dry beer?

[Capn Ahab]

As it only affected a few bottles I doubt it's autolysis. Could be any old bacteria or wild yeast that was left on those particular bottles. Rubbery is an unusual flavour descriptor for beer infections though...

[orlando]

My money would be on those bottles infected being ones that may not have received as good a sanitation and that's where the infection occured. Although wild yeast tends to promote gushers rather than the flat beer you mention.

[gregorach]

Looks like there's carbonation in it (as you would expect), just that it's not holding a head... Which suggests the culprit is producing some kind of protease which is breaking down the proteins required for head retention. Doesn't really narrow the field any though... You'll never figure out what it is without doing some proper analytical microbiology - there are just too many possibilities. We're not even going to be able to figure out if it's a yeast or a bacterium.

[greenxpaddy]

You could heat it to 50 degrees C to see if it kills it off. Then it is probably a yeast but not one you would want to reclaim

[Befuddler]

Looks like there's carbonation in it (as you would expect), just that it's not holding a head... Which suggests the culprit is producing some kind of protease which is breaking down the proteins required for head retention. Doesn't really narrow the field any though... You'll never figure out what it is without doing some proper analytical microbiology - there are just too many possibilities. We're not even going to be able to figure out if it's a yeast or a bacterium.

I thought as much, but it was worth an ask in case anyone's had a rubbery beer before.

I just wafted it under my girlfriend's nose and she reckons it's got a hint of acetone about it, which would be a much more common flaw. On the other hand, her nose and palate are famously shit, and it still smells of rubber to me.

You could heat it to 50 degrees C to see if it kills it off. Then it is probably a yeast but not one you would want to reclaim

Wouldn't that kill most bacteria as well? Either way, I can't be arsed to fanny about with it. I'll leave this half bottle as is and see what happens to it over the coming weeks, purely in the interests of science.

[liquidman]

I think Paddy means that anything that is still alive after heating to 50 degrees is likely to be wild yeast rather than a bacterial infection.

A