Mysterious tainted beer. Change in flavor and color of a soured beer in secondary.

[JBCSL]

I had a chance to check the gravity of the darkened beer. In the 3 weeks from my last test just before I cold crashed it, it went from 1.005 to 1.003, so there was a change when the color changed.

The first picture shows a new dark line towards the top of the carboy, where it is either settling or growing.

Looking back at the flask I filled with trub, there appears to now be a thin discolored layer above the other liquid that had cleared out back to normal. (second picture)

The last picture is a glass pulled from each showing the difference in color. Taste wise, the discolored beer isn't bad, just different. The light one has strong peach and brett presence, where as the darker one has more of the leathery character of a Flanders.

For science I added a little corn sugar to the carboy to try to kick up some fermentation, since the OP's bottles cleared after bottle conditioning, to see if that was what sparked the change back. Will report back when I have something to report.

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[killsurfcity]

Yes, so the theory we've been working with is essentially that. Here's what we know:
- This does not happen to all samples from the same batch
- We were careful not to splash during transfers, but typically did not use CO2
- It seems to be continued fermentation that holds the color change off
- The area where the beers are kept does get very cold at certain times of year
- Refermentation in the bottle or carboy changes the color and flavor back

I think you're right about the flask. I'm not surprised it cleared so fast. If the action caused any further yeast and bacteria activity, I think it'd be enough to digest whatever compound causes the color and flavor change. We've since bottled a batch or two with this issue, and they clear right up in a day or so from bottle conditioning.

 

[m00ps]

You think this could just be another random symptom of the "sick" period a lot of sour beers go through? Maybe brought about from transferring or small degrees of oxygenation?

 

[killsurfcity]

No. The "sickness" is a bloom of pediococcus, which can take months for Brett to clean up. The "taint" we're describing here is not related to that in any way I can think of, other than that it happens to beer.

 

[JBCSL]

Finally had some action in the carboy. 3 weeks since I transfered and 2 weeks since I added the corn sugar it just started growing a new pec layer.

Also the lower part below the dark layer has turned back to very close to the original color, although its a little tough to tell in the picture since it was taken in a dark closet with a flash. For easier comparison the bottom picture shows the color after the original transfer.

Will continue to report the changes for science and so anyone in the future that has this issue can know exactly what to expect.

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[JBCSL]

7 days later and it has completely changed back to its original color. No trace of the darkness whatsoever.

 

[killsurfcity]

Well, it's been a few years! I'm circling back to update this thread with what I think is a resolution to my initial question. I am 99% sure the "taint" we are discussing is due to high dissolved oxygen in the beer at packaging, due to rough racking, or other agitation during movement or transfer. I now work in a commercial brewery and see have seen this in multiple beers. It tends to happen to canned IPAs every so often, and to a much much lesser extent sour beers. They initially react the same, by taking on a muddled taste and ruddy appearance, however, while the IPA will be irreparably damaged by this, the sour beer, if it is bottle conditioned, will turn back around as brett and bacteria do their work at scavenging all that oxygen. To sum up, if you bottle a sour beer and find that the first couple bottles look muddled and taste off, just let it sit a month and try again. Time should work it out. Thanks to everyone who contributed to this thread!

 

[monkeymath]

Well, it's been a few years! I'm circling back to update this thread with what I think is a resolution to my initial question. I am 99% sure the "taint" we are discussing is due to high dissolved oxygen in the beer at packaging, due to rough racking, or other agitation during movement or transfer. I now work in a commercial brewery and see have seen this in multiple beers. It tends to happen to canned IPAs every so often, and to a much much lesser extent sour beers. They initially react the same, by taking on a muddled taste and ruddy appearance, however, while the IPA will be irreparably damaged by this, the sour beer, if it is bottle conditioned, will turn back around as brett and bacteria do their work at scavenging all that oxygen. To sum up, if you bottle a sour beer and find that the first couple bottles look muddled and taste off, just let it sit a month and try again. Time should work it out. Thanks to everyone who contributed to this thread!

What happened to "it's not oxygen!!" ?

No, seriously, thanks for reporting back! I just read through this thread and the other cross-referenced one. Very scary stuff, but it's encouraging to hear the effect appears to be reversible (which oxidation, per se, is not), at least for sour beers (and who cares about IPAs).