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

I've been brewing mostly sour beers for the past few years, with relative success, but recently I had a totally baffling issue. I figured maybe someone had come across this or heard of it, so here goes...

My brewing partner Matt and I have a 65g wine barrel, we've been using as a Solera for a Belgian Golden sour ale. We've only racked and replenished beer in it twice so it's fairly new. Our first batch out, was split and aged with a few kinds of berries, and it was great. The most recent batch as treated similarly. Broken into four carboys; straight, with grapes, with raspberries, dry hopped.

When last we checked on them, I noticed that a couple looked darker than I remember. I wrote it off as a trick of light or something, and paid it no mind. However, two days ago we we're set to bottle, and while racking we pulled a sample of the straight beer (yes, racked to secondary and nothing was added). It was clear then that something was wrong. The beer in the barrel is a beautiful clear golden color, but the beer in the carboy had turned a muddy purple-brown. And the taste... It's alright up front, but toward the end, It cuts into this odd, metalicy, papery, weirdness, that we can't figure out. We checked the other carboys and sure enough it'd taken 3 out of 4.

This is what is so baffling. All three carboys were treated exactly the same from what we know. Cleaned with Oxiclean, rinsed, and sanitized with Star-San. And yet, for some reason, the raspberry one is the only one that wasn't tainted in some way. We'd obviously really like to know what happened so we can avoid it in the future. As I'm sure you know, losing 20g of beer you've been sitting on over a year is no fun.

This isn't my image, but this is exactly what ours looked like. Ever heard of this?

The tastes you are decribing sound like the reult of oxidation. Air pickup can also darken beer somewhat. I feel your pain-- there is so much time invested in these beers that it's tragic to have such a result.

Not so sure. When this happened to my berlinner weisse (kegged and under cO2) it happened within a day or so

I seriously doubt simple oxidation is the cause. The bugs in this beer, will form a pellicle in a day or so that protects them from oxygen anyway, not to mention that the transfer process tends to generate some c02. Yes the taste is similar to oxidation, but not the same. for instance, the metallic component. (no metal touched the beer btw)

What is most baffling is the color. This is not a shade darker, it's completely different. It was the golden yellow, and now it is crap brown. I don't even know how to describe the sediment... a blackish purple sludge at the bottom of the carboys. It's almost like someone poured liquid ash into the beer.

This is no run of the mill common noobie homebrew problem, we're well past that. This seems like a chemical reaction of some kind. But with what? a clean and sanitized glass carboy? hence the baffle...

In an attempt to recreate the issue we had with the beer, we took a sample of another one of our sours, and added a dose of pure oxiclean solution to it. After two days this test is showing to be inconclusive. There is always a chance it will turn at some point, but the beer has already outlasted the period of time it took to taint previously.

We may attempt the same test with star-san and see if that goes anywhere.

I assume you know about this thread:
https://www.homebrewtalk.com/f127/color-change-after-bottling-224631/

Maybe try mixing oxiclean and star-san together, it sample jar, let it sit out a few minutes, then add your beer. My guess is there is some chemical reaction with the use of oxiclean-starsan-oxygen-beer, and its "burning" the beer?

Also "Tom" on babble belt had the exact same thing happen. Everything went bad except the portion he racked onto cherries:
http://www.babblebelt.com/newboard/thread.html?tid=1108752780&th=1364313226&pg=1&tpg=1&add=1

Yeah, I'm going to post a comment there as well, as it looks like conversation is picking up.

I'm also Ethan from babble belt, btw.Wasn't sure how much crossover there was between this forum and that. I'll try the star-san + oxiclean test and see what that does.

I did the star san/oxy clean mix. I'll report back.

I had a similar issue recently with a beer that noticeably reddened after being bottled.

https://www.homebrewtalk.com/f36/beer-darkened-during-bottling-402445/

It's a complete mystery to me as it should have ended up a nice golden yellow.

It looks like you have a similar issue, specifically noting the purplish hue in the finished beer. It cracks me up that people as still saying oxidation. I really wish people would actually give this some thought instead of saying the same old; infected, yeast haze, oxidation, BS.

Our sour beer, oxiclean, star san blend has been sitting for a couple weeks now with no color change. The plot thickens. I wonder if there's any way this could be a reaction to metal in some way. Like how in recipes that use acids like vinegar, they say to mix in a "non-reactive" bowl...

Some of this beer was in a stainless pot at one time. Is there a chance if it wasn't "charged" properly, or if the coating was damaged, it could react in this way? (Forgive me, I know little of stainless chemistry)

duanestorey said:

I had a similar issue recently with a beer that noticeably reddened after being bottled.

https://www.homebrewtalk.com/f36/beer-darkened-during-bottling-402445/

It's a complete mystery to me as it should have ended up a nice golden yellow.

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Did you reach any conclusions. I have the same problem with my bottle beer. I don't bottle often but when I did I notice the color going darker. No off flavors so I can't think is a bug or oxidation !?

I have no idea if this is helpful, but I can tell u about a chemical reaction trick I use sometimes that sounds applicable. I do some woodworking, and if you want to make clean wood look aged, you do the following... Put vinegar in a jar with steel wool. When it turns color u wipe it onto the wood and it grays it. Guess what color the magic mixture is- purply Brown. So u have sour acids contacting stainless steel that may not be completely passivated? That could have something to do with it.

tedclev said:

I have no idea if this is helpful, but I can tell u about a chemical reaction trick I use sometimes that sounds applicable. I do some woodworking, and if you want to make clean wood look aged, you do the following... Put vinegar in a jar with steel wool. When it turns color u wipe it onto the wood and it grays it. Guess what color the magic mixture is- purply Brown. So u have sour acids contacting stainless steel that may not be completely passivated? That could have something to do with it.

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This is the best hypothesis I've heard so far. I didn't even think of passivation. It was a long time ago, but I think we may have used a brew-pot to hold some beer while we racked other things. That could be it! I'll have to try a steel wool test and see what the resulting solution looks like. I could easily identify it just by eye now. This also explains why when a friend kegged a berliner I did, it turned out the same. If for some reason his keg wasn't passivated, there's your answer.

Digging up this old thread for science!

We have some new information. So, last time we went to bottle our barrel beers, we were met with two more (out of 4, 5g) tainted batches. I can't even tell you how big a blow that was. That's now 20g of an absolutely gorgeous beer that has been rendered undrinkable. During the flurry of expletives that followed, we began pouring over the details, trying again to figure out what had gone wrong. A couple things came to light...

1) We rack beer out every 6 months. Only batches that have wintered have developed the "taint"
2) We always fruit 2 batches, the other two are straight, and dryhop. However, we let those sit a few months after racking while the fruit beers mature. Only non-fruited beers have ever acquired the "taint"

This is a huge discovery, and possibly the key to cracking this mystery. Here's our new hypothesis; the "taint" is in part, some kind of reaction by the microbes to the onset of cold. We do not know how cold the basement the beers winter in gets, (off site location) but there's a chance it is near freezing at some points. The fruited beers don't suffer taint, because they enter a period of refermentation, which raises the temperature out of the danger zone.

An obvious question is... Why if cold affects the beer in this way, does the "taint" not take place in refrigerated bottles? In short, we don't know. There must be some other factor at work in combination with the cold. Perhaps oxygen is introduced, but pellicle re-formation is somehow inhibited by the cold? Or, maybe the pressure exerted by bottling works as a preservative against the taint?

Now, for the real kicker...

Once we saw we had an issue again, after much cursing, hitting of inanimate objects with fists, etc. we decided to compare this new taint with the old one. We had kept some bottles to send to a lab and never got around to it. So we fished a couple out and opened them... only to find... DUN, DUN DUUUNNNNN... completely beautiful, sparkling clear beer! W. T. F.
Somehow, the smell, the taste, it was impossible to detect anything had ever been "wrong". The beer was beautiful, sour, and delicate, as the best of our regular sours are. This is by far the most baffling thing I've experienced in brewing. We decided to label the bottles as Lazarus in honor of it's cheat of death.



Due to this new discovery, we have saved our last two tainted batches, and will check their progress this week. We may just bottle them up and see if they clear.

For anyone who doubts oxygen is the cause. Pour a glass of a sour beer and stick it somewhere out of the way for two weeks. Compare it to a fresh bottle. I did (as I posted in the other thread) and the color change was dramatic!

Any chance some like Purple bacteria, which includes some species of Acetobaceter?

Beer darkening some in a poured glass left in an open environment doesn't prove anything useful, except maybe that beer can darken under "x" conditions. "X" being god knows what, as you didn't really provide any controls for that experiment, iirc. Correlation ≠ causation.

I think saying it's just oxygen is a cop out, (homebrewers say every malady is oxygen. Most of them are likely infection, imo.) it's clearly more complicated than that, although that could be a factor. I would note again, these beers were transferred very carefully, with an absolute minimum if any splashing. Any oxygen pickup would be only on the surface after racking, which should just stimulate activity in brettanomyces, and trigger pellicle reformation. We are talking about around 35% young (less than 6 months) beer here. It also doesn't happen all the time, only to beer cellared during cold months.

I've made a lot of sour beer, and I'm very aware of the color change that can happen during oxygen exposure under normal conditions. This is not that. I'll also say I've splashed beer all over during transfers before, even straight up poured from one bucket to the other with no noticeable ill effect to the beer. (not that i would recommend it) It takes a lot more oxygen than most home brewers think to ruin a beer.

Oldsock, did the beer you left out ever turn clear again? These went from clear, to ruddy purple brown, to clear again. Flavor went from great, to off to the point of being barely drinkable, to great again.

I've never heard of purple bacteria, but maybe that has something to do with it. Hard to tell without lab work. We are racking another batch soon, and plan to use a chamber to keep heat from dropping so far this time, we'll see what that does.

I have left samples of turbid mashed lambic around 6-8 months old out over night (forgot to dump them). They went distinctly purple and cloudy.

killsurfcity said:

Digging up this old thread for science!

We have some new information. So, last time we went to bottle our barrel beers, we were met with two more (out of 4, 5g) tainted batches. I can't even tell you how big a blow that was. That's now 20g of an absolutely gorgeous beer that has been rendered undrinkable. During the flurry of expletives that followed, we began pouring over the details, trying again to figure out what had gone wrong. A couple things came to light...

1) We rack beer out every 6 months. Only batches that have wintered have developed the "taint"
2) We always fruit 2 batches, the other two are straight, and dryhop. However, we let those sit a few months after racking while the fruit beers mature. Only non-fruited beers have ever acquired the "taint"

This is a huge discovery, and possibly the key to cracking this mystery. Here's our new hypothesis; the "taint" is in part, some kind of reaction by the microbes to the onset of cold. We do not know how cold the basement the beers winter in gets, (off site location) but there's a chance it is near freezing at some points. The fruited beers don't suffer taint, because they enter a period of refermentation, which raises the temperature out of the danger zone.

An obvious question is... Why if cold affects the beer in this way, does the "taint" not take place in refrigerated bottles? In short, we don't know. There must be some other factor at work in combination with the cold. Perhaps oxygen is introduced, but pellicle re-formation is somehow inhibited by the cold? Or, maybe the pressure exerted by bottling works as a preservative against the taint?

Now, for the real kicker...

Once we saw we had an issue again, after much cursing, hitting of inanimate objects with fists, etc. we decided to compare this new taint with the old one. We had kept some bottles to send to a lab and never got around to it. So we fished a couple out and opened them... only to find... DUN, DUN DUUUNNNNN... completely beautiful, sparkling clear beer! W. T. F.
Somehow, the smell, the taste, it was impossible to detect anything had ever been "wrong". The beer was beautiful, sour, and delicate, as the best of our regular sours are. This is by far the most baffling thing I've experienced in brewing. We decided to label the bottles as Lazarus in honor of it's cheat of death.

Due to this new discovery, we have saved our last two tainted batches, and will check their progress this week. We may just bottle them up and see if they clear.

Click to expand...

Wow! That is very interesting. I am eager to see if the freshly tainted ones come back to life!

TimT said:

I have left samples of turbid mashed lambic around 6-8 months old out over night (forgot to dump them). They went distinctly purple and cloudy.

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Perhaps it's the bacteria Oldsock mentioned. I think we may have to work out a way to limit exposure to the air unless refermentation is active. Maybe there is in fact a sour beer spoiler out there. Well, at least it gives back what it takes!

killsurfcity said:

Beer darkening some in a poured glass left in an open environment doesn't prove anything useful, except maybe that beer can darken under "x" conditions. "X" being god knows what, as you didn't really provide any controls for that experiment, iirc. Correlation ≠ causation.

I think saying it's just oxygen is a cop out, (homebrewers say every malady is oxygen. Most of them are likely infection, imo.) it's clearly more complicated than that, although that could be a factor. I would note again, these beers were transferred very carefully, with an absolute minimum if any splashing. Any oxygen pickup would be only on the surface after racking, which should just stimulate activity in brettanomyces, and trigger pellicle reformation. We are talking about around 35% young (less than 6 months) beer here. It also doesn't happen all the time, only to beer cellared during cold months.

I've made a lot of sour beer, and I'm very aware of the color change that can happen during oxygen exposure under normal conditions. This is not that. I'll also say I've splashed beer all over during transfers before, even straight up poured from one bucket to the other with no noticeable ill effect to the beer. (not that i would recommend it) It takes a lot more oxygen than most home brewers think to ruin a beer.

Oldsock, did the beer you left out ever turn clear again? These went from clear, to ruddy purple brown, to clear again. Flavor went from great, to off to the point of being barely drinkable, to great again.

I've never heard of purple bacteria, but maybe that has something to do with it. Hard to tell without lab work. We are racking another batch soon, and plan to use a chamber to keep heat from dropping so far this time, we'll see what that does.

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The control in my case was that the beer that remained in the bottle while the other one was exposed to the air. The control did not turn purple. You could certainly argue that something besides oxygen was the cause of the darkening in the beer that was left exposed to the air. That glass was not cleaned with OxiClean or Star-San. I'm not claiming that oxidation is the answer necessarily, the darkening could be a caused by a microbe that thrives in aerobic conditions for example. I'm simply stating that oxygen is the most likely factor so far identified as the color change usually follows transferring and exposure to oxygen.

Oxygen pickup even with minimal splashing can be significant unless you are purging the receiving vessel with CO2. Effectiveness of Various Methods of Wort Aeration: "Even when splashing was minimized by allowing the water to flow into the bottom of the plastic fermentor bucket, the dissolved oxygen content was significant (43% of saturation) prior to any active attempt to aerate the water."

The first time I witnessed the darkening of a sour beer was a sour beer I kegged in September. So my experience doesn't agree with your observation about cold weather. My sours often sit around 50F during the winter, and I've bottled many before, after, and during that time without issue. However I rarely keg sours, so the lack of activity could be part of it.

After I saw the color change in the beer, I dumped it. Hadn't heard (or seen in the case of the other beer) any improvement. Sounds like we need one of those goose-neck flasks that Pasteur used to see if the same color change happens when pasteurized beer is exposed to oxygen.

Oldsock said:

The control in my case was that the beer that remained in the bottle while the other one was exposed to the air. The control did not turn purple. You could certainly argue that something besides oxygen was the cause of the darkening in the beer that was left exposed to the air.

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That's really what I'm arguing. I'm unconvinced about the oxidation argument. Brett being antioxidative after all.

Oldsock said:

the darkening could be a caused by a microbe that thrives in aerobic conditions for example. I'm simply stating that oxygen is the most likely factor so far identified as the color change usually follows transferring and exposure to oxygen.

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This is the most frightening scenario. My worry is that if such a microbe takes hold we could have a much larger problem on our hands.

Oldsock said:

Oxygen pickup even with minimal splashing can be significant unless you are purging the receiving vessel with CO2.

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Sure, but constant splashing throughout transfer and a splash or two at start of transfer are very different things. Much like water and beer. Besides, doesn't someone (Palmer?) say that the splashing of un-carbonated beer generally releases CO2?

Oldsock said:

The first time I witnessed the darkening of a sour beer was a sour beer I kegged in September. So my experience doesn't agree with your observation about cold weather.

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Interesting. That was where we first noticed it too. Did you transfer into a keg flushed with CO2? You didn't chill the keg during carb? Cold may not have anything directly to do with it. It may be that fermentation, even very slow fermentation is enough to stave off this taint/infection. In summer the beer is likely still fermenting in the hot weather, whereas it could be halted (at least restricted to certain less effective microbes) during winter. Also the beers that have survived have all been fruit beers, which were refermenting in buckets over winter. This would mean they both had a higher temp, and less oxygen exposure over all.

Oldsock said:

My sours often sit around 50F during the winter, and I've bottled many before, after, and during that time without issue. However I rarely keg sours, so the lack of activity could be part of it.

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I guess in that case it's safe to assume, your sours are sitting under CO2 at that time, which is a reasonable control. (Though this basement gets closer to 40s) My basement never gets that cold, but i've never had this issue in my personal stuff. Only at this off site location.

Oldsock said:

After I saw the color change in the beer, I dumped it. Hadn't heard (or seen in the case of the other beer) any improvement. Sounds like we need one of those goose-neck flasks that Pasteur used to see if the same color change happens when pasteurized beer is exposed to oxygen.

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The most difficult aspect of this to wrap my head around is that the beers come back. We need to do more serious batch to batch comparisons, but it appears as of now that there is no notable change once the taint passes.

To hypothesize a bit more... perhaps fermentation can clear the purple taint away. Maybe the tainted bottles we have went through enough of a refermentation to drive off/breakdown/etc. the purple compound. Whereas, if we left some from the buckets sit out, it won't clear back up, no refermentation. The tainted beers did have pellicles though, but who knows how long they took to form.

My brew partner and I have just decided, we will be bottling the tainted beer this weekend and reserving samples of each in glass jugs for further observation. One of the bottles of each will be clear glass, so we can watch it daily and note exactly if/when/how a change occurs. We will post back with results. Thanks for the input everyone.

For what it is worth, I've had sour beer get oxidized very badly to the point where it turned from an orange to nearly purple in the fermenter. The cardboard flavor was unmistakable, so if you or your friends can't taste oxidation, then maybe it is something else.

On a side note, as the beer ages, I believe it is losing some of that cardboard flavor. I've decided to hold onto it just to see what happens.

Anyone see that movie "bottleshock"? About the early days of wine in Ca? In the instance it shows the wine going to a different color then changing back.... It's on netflix. Sorry I couldn't be of more help, but it sounds similar....

I had the purple colour change happen to me.

I soured worted a Berliner Weisse, and it was the standard straw/golden color before I boiled it for 15 mins. Cooled it into the fermentor and it had changed to a pinkish purple color. I did take a hydrometer reading before the boil and it was at 1.008. I disregarded it thinking it was some strange lacto thing, but now I'm thinking along the lines that it was fermented out by wild yeast on the pitched grain for lacto, or it was an alcohol producing lacto strain.

Pitched neutral ale yeast that did nothing, no ferment at all. I left it for a month with no change to color. Did another batch of wort, blended that in and fermented with ale yeast. Color is back to golden.

I've had a similar issue with two recent brews. Not sure if it is the same, but allow me to explain.

My latest brew was a New Zealand Pale Ale that was originally a pale golden color. The beer was bottled in early August. I bottled the beer as I normally do and have had about 4 bottles of it in the last two weeks.

At first, the beer had a strong bitter taste with a sweet malt backbone that was actually quite pleasant. I declared the beer to be one of my best after the first bottle. A few days later I opened another beer and the first thing I noticed that was different was a darker color. The color is hard to describe but a good way to think of it is to imagine sapping the light from within the beer. There is a dark shadowy outline around a golden core that is less vibrant than what it was before. This "taint" got worse right up until the last bottle I had which was on Sunday. I would describe the flavor as "wet socks" and "papery" but it is quite hard to describe for me. The bitterness is less sharp and overall the beer has changed dramatically.

My only theory so far, backed up by the fact that I just recently started getting lazy about my chilling process, is Hot Side Aeration. I oxygenate my beers by shaking post boil after chilling. This beer was splashed at around 90-100 degrees. So was another beer brewed in July that had the exact same issue. Tasted great up until bottling, then quickly degenerated with a dark taint.

I had a second theory that dramatic temperature changes during storage caused the taint. These beers were brewed and stored during peak summer temps. I store my bottles in an extra room of my house that I recently moved into, and it could be that this room experiences sudden temperature changes. However, my other beers aren't experiencing this issue.

Sorry for the long post. I can provide pictures if anyone actually reads my rant

budai said:

I've had a similar issue with two recent brews. Not sure if it is the same, but allow me to explain.

My latest brew was a New Zealand Pale Ale that was originally a pale golden color. The beer was bottled in early August. I bottled the beer as I normally do and have had about 4 bottles of it in the last two weeks.

At first, the beer had a strong bitter taste with a sweet malt backbone that was actually quite pleasant. I declared the beer to be one of my best after the first bottle. A few days later I opened another beer and the first thing I noticed that was different was a darker color. The color is hard to describe but a good way to think of it is to imagine sapping the light from within the beer. There is a dark shadowy outline around a golden core that is less vibrant than what it was before. This "taint" got worse right up until the last bottle I had which was on Sunday. I would describe the flavor as "wet socks" and "papery" but it is quite hard to describe for me. The bitterness is less sharp and overall the beer has changed dramatically.

My only theory so far, backed up by the fact that I just recently started getting lazy about my chilling process, is Hot Side Aeration. I oxygenate my beers by shaking post boil after chilling. This beer was splashed at around 90-100 degrees. So was another beer brewed in July that had the exact same issue. Tasted great up until bottling, then quickly degenerated with a dark taint.

I had a second theory that dramatic temperature changes during storage caused the taint. These beers were brewed and stored during peak summer temps. I store my bottles in an extra room of my house that I recently moved into, and it could be that this room experiences sudden temperature changes. However, my other beers aren't experiencing this issue.

Sorry for the long post. I can provide pictures if anyone actually reads my rant

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To me it sounds like oxidation with the papery taste and I have read that oxidation can change the color as well.

killsurfcity said:

My brew partner and I have just decided, we will be bottling the tainted beer this weekend and reserving samples of each in glass jugs for further observation. One of the bottles of each will be clear glass, so we can watch it daily and note exactly if/when/how a change occurs. We will post back with results. Thanks for the input everyone.

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I know this is a year and a half ago but I was hoping to hear an update on what happened with your second tainted batch after you bottled it. Just had this happen to me and was looking for some insight if time is going to heal it.

My darkening happened in primary after I cold crashed it for transfer to secondary. Was brewed in early august with danstar belle saison yeast and dregs from tilquin, crooked stave, and a allagash coolship, all pitched at the same time. I was planning on using some of the sediment to start another batch last week, but I got a cold and had to postpone it, so instead of crashing it for a couple days, it was cold for just over 2 weeks. Right at about the 2 week mark I noticed it was a little darker, then the next day it was a lot darker, so the transformation was quick and not at the immediate onset of cold. Here is a picture of the batch in secondary.

So I decided to save a flask of the trub anyway incase this was salvageable for another batch and something weird happened. When I checked out the flask this morning it settled out to the original color!?!

The only theory I have is the unsettling of the trub woke up some bugs that quickly ate up what ever was causing the brown but I don't know how plausible that would be in 24 hours? Maybe your bottles cleared after the priming sugar woke up your bugs and they did the same?

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Apologies for not posting my results, got a bit busy... for a year. Haha

Anyway, literally everything this happened to has now cleared, and some of them are excellent beers. Oddly they are somewhat changed. The best I can explain it, there's an additional small citric acid like bite to the tartness. It's a minor difference, but it's there.

As far as the cause, we have no clue. I'm tempted to think it's somehow picked up from the air during bottling, but it could be one of the microbes in a mixed culture that does this. Either way, we have been using a lot of CO2 in bottling recently and haven't had any more issues.
I don't think it's standard oxidation, I'm pretty familiar with that flavor, as the positive version of it is one of my favorite flavors in old beer, sherry, and madeira. That's not what this is like, I don't think I could adequately describe it. At least I know it goes away and doesn't harm the beer. It's almost like Pedio ropiness. When you find it it's kind of a bummer because you have to wait for it to clear, but when it does the beer is great. Still I'd love to know once and for all what's happening.

JBCSL, that's essentially what ours looked like. In fact you've almost replicated our results exactly. It's strange enough to see a beer go dark like that, it's so much stranger to see it clear again. It's just something you think would not be possible.

It's also interesting you got it after cold crashing. The first time we saw it was with a no-boil berliner that got kegged. IIRC it was fine for like a day and then went dark. Got dumped before it cleared unfortunately.

Awesome, that's what I was hoping to hear. The sample I pulled from this batch before the color change was absolutely incredible and I was devastated when I thought it went bad.

So to theorize, in all likelihood there is some microbe in the mix that wakes up at a low temp and starts kicking out something to turn it dark, then as time goes on something else eats up the dark stuff and turns it back? Sounds plausible enough I guess.

I checked the gravity before I cold crashed but not again after the darkening, my next step is to check that to see if there was any noticeable change there to give some sort of hint as to what is going on.

The thing that really gets to me though is how quickly the flask of trub I pulled cleared, as it was back to normal color within 24 hours. The only change so far in my carboy is that the top inch is noticeably darker than the rest of it.

The differences I can recall between the two are that I purged the carboy with CO2 but not the flask, although I doubt that would have made and impact. But what I'm leaning towards is the kicking up off all the yeasties and other bugs in the trub went to quick work eating up all the dark and clearing it that way.

I'm going to try a couple experiments to see if I can isolate what it is that triggers the change back to normal and will report my findings.

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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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.

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?

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.

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

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!

killsurfcity said:

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!

Click to expand...

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).