Beer Mysteriously Darkening

I'm an all grain brewer and I bottle condition. My recent beers, however, have been suffering from a darkening problem. Very light beers wind up turning brown-ish and almost muddy looking after a little time in the bottle. I'll try to give as many clues as possible. The first picture attached is an American Wheat that was supposed to have an SRM of 5.6, but it obviously is much darker than that. The color on this beer was much lighter when I took my gravity sample before bottling (see second picture), but then two weeks later it had gotten a lot darker. It is also a lot darker towards the bottom of the bottle, and the yeast at the bottom of the bottle is the darkest of all.

A brewer tried the beer (after two weeks of carbonation - already darkened) and I asked him about the problem. He said that it looked like oxidation but that he didn't taste any oxidation. And oxidation would seem a little weird after only 2 weeks in the bottle.

The color problem seems to coincide a bit with when I started paying attention to water chemistry, i.e., adding lactic acid, gypsum, and calcium choride using the Bru'n water spreadsheet. I don't know if that has anything to do with it.

Please help!

It does look like oxidation - that sort of dull brown color. Nothing else had changed with your process besides the water treatments? I would think hitting the correct pH would only improve things - are you measuring pH?

Well, color changes depending on how much fluid you're looking through. In a glass (and moreso in a carboy), there's much more material to trap light than inside tubing or inside a hydrometer flask. So having it darker in a glass is expected.

Oxidation will indeed darken the beer. Haze can make the beer look darker, as less light gets through. Yeast can make the beer look lighter.

Are you using finings and doing a full length, good strength boil? How long are you fermenting? Is the beer dropping clear before you bottle? Are you kicking up a whole bunch of sediment when you bottle? Are you leaving the sediment inside the bottle when you pour? That's a hazy, murky looking beer, which may be part of why it's looking so dark.

To the first question, I have not begun measuring pH yet, just relying on the Bru'n water chart for now.

To the second question, that's very interesting. I do a full boil but have not been using finings much recently as I prefer my beer to be hazy. I also use a lot of oats, wheat, and rye in my pale beers for mouth feel. I also would not say that my beers drop clear before I bottle. So you think part of the problem could be that there is just a lot of particulate in the beer? What would you recommend as a solution?

And thanks so much, this is really helpful.

Also I ferment for two weeks and when I bottle I may kick up some sediment because I rack from the primary right to the bottling bucket.

Yeah both samples are pretty cloudy I agree making it a little harder to judge, it just seemed like a fairly significant color change unless it's a trick of the light (that's the finished hydrometer sample on bottling day?). If it's just sediment then cold conditioning the bottles should settle it out. Can't help think there's more going on.

Not necessarily particulate. If you're not using any finings, you may be getting a lot of protein haze, which can give a darker murky looking beer. Yeast haze can look pale whitish (think Hefeweizen). But if you're kicking up sediment and not giving it time to clear, and then pouring it all into the bottle, you'll definitely have particulate matter in addition to protein haze, which can give you that muddy looking beer, which can certainly make the beer look opaque and darker. If that's what you're going for, cool, carry on, you often can't taste it, but I'm pretty big on clear beer.

But I'll agree with the first responder that it may well still be oxidation, even if other brewer couldn't yet taste it. Oxidation can actually darken a beer, and do it fairly rapidly.

I also have been taking a long time to cold crash the wort after the boil due to extended whirl pool additions. Could be adding a chill haze resulting in more particles in the beer? I can say that storing the bottles cold for a while doesn't help. Maybe it's that too many particles are getting into the beer in the first place

The hydrometer sample is extremely cloudy, even for a wheat beer, so I wouldn't expect the beer to be clear if you bottled right after this hydrometer sample was taken.
Give your beer at least another week in the fermentor to clear. Move your fermentor the day before, if you need to move the fermentor, when getting ready to the rack to the bottling bucket. Hold your siphon off the bottom of the fermentor to avoid excess yeast and trub in the bottling bucket.

bpalfrey10 said:

The color problem seems to coincide a bit with when I started paying attention to water chemistry, i.e., adding lactic acid, gypsum, and calcium choride using the Bru'n water spreadsheet. I don't know if that has anything to do with it.

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Are you checking the tab on the Bru n' Water sheet which tells you your estimated mash pH? I've heard that lighter beers darken over time because my mash pH was too high, and if you're adding a bunch of bicarbonate to match a certain Bru n' Water style you might actually be pushing your pH too high.

I've had bottles oxidize in 10 days flat, but if you don't taste anything then it's probably not that.

I have been checking estimated mash pH tab, shooting for 5.2 pH every time.

So as I understand it, there are two possible problems. Oxidation and excessive particulate.

(1) To handle the particulate, I'll use finings (maybe both Irish moss and whirlfloc), cold crash before bottling, and take steps to minimize sediment pickup at all steps. Also leave it in the fermenter longer. Is cold crashing before bottling a good idea? I have a keezer I could put the fermenter in.

(2) As far as oxidation, I can't figure out the issue. I don't stir the mash, do all of my runnings into one big pot that goes on the boil, I then chill right in that big pot. Then pour it into a bucket (primary fermenter) and oxygenate. When its time to bottle I rack from the primary fermenter into a bottling bucket then use a spigot and bottling bucket to fill up bottles and cap with O2 absorbing caps. So while I'm not using CO2 or anything, I can't find anything in my process that would result in the color darkening that much in 2 weeks.

Anybody have any other ideas or things I could do differently? I'd feel much better about my beer if I figured this problem out.

And thanks again, you guys are great.

Well, somehow I just deleted my whole response, so here goes trying to redo it:

bpalfrey10 said:

I have been checking estimated mash pH tab, shooting for 5.2 pH every time.

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Are you making sure that you're adjusting to proper volumes in both the water additions tab, and in the mash acidification tab? Are you entering your grain bill accurately? And how confident are you in your source water? There's a pretty large degree of seasonal variability in a lot of water supplies. If the actual alkalinity is higher than you think it is, you could indeed be getting too high of a pH.

So as I understand it, there are two possible problems. Oxidation and excessive particulate.

(1) To handle the particulate, I'll use finings (maybe both Irish moss and whirlfloc), cold crash before bottling, and take steps to minimize sediment pickup at all steps. Also leave it in the fermenter longer. Is cold crashing before bottling a good idea? I have a keezer I could put the fermenter in.

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You don't need to use Irish Moss AND Whirfloc. They're essentially the same thing, and if you use both, you can overdo it. I would just use whirfloc. Make sure you're getting a good strong rolling boil so you're getting a good hot break. If you're using a continental Pils malt (German or Belgian) you may actually get some help from doing a protein rest, but if you're using American or UK malts that'd do more harm than good. You could also use post-fermentation finings (PVPP, gelatin, isinglass, etc). As long as the beer has full fermented and conditioned (no residual diacetyl/acetaldehyde, etc), and you get it to drop clear, either from time or cold crashing, you should be good to go. Doesn't necessarily mean you have to leave it longer, but generally leaving it longer won't hurt. Cold crashing would certainly speed the process, but don't do it until the beer has fully conditioned and cleaned up after itself post-fermentation.

And then make sure you're not dumping the yeast from the bottom of the bottle into the glass, or you're defeating the whole point.

Also, are you doing a vorlauf? That was a reason I stopped doing BIAB, I found that being able to vorlauf and get clear wort into the boil kettle gave me clearer final beer.

(2) As far as oxidation, I can't figure out the issue. I don't stir the mash, do all of my runnings into one big pot that goes on the boil, I then chill right in that big pot. Then pour it into a bucket (primary fermenter) and oxygenate. When its time to bottle I rack from the primary fermenter into a bottling bucket then use a spigot and bottling bucket to fill up bottles and cap with O2 absorbing caps. So while I'm not using CO2 or anything, I can't find anything in my process that would result in the color darkening that much in 2 weeks.

Anybody have any other ideas or things I could do differently? I'd feel much better about my beer if I figured this problem out.

And thanks again, you guys are great.

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First thought: hot side aeration is a boogeyman, so don't worry about not stirring the mash. Not stirring is good for maintain temp, but you then have to worry about hot spots, and it may not remain consistent. On the other hand, if you stir too much, the worry isn't oxidation but rather just losing too much temperature. I wouldn't INTENTIONALLY try to aerate hot wort, but in the case of a SEVERE stuck mash (or if the false bottom comes disconnected or something, which has happened a couple times), I've had to resort to dumping the entire mash out of my MLT into a kettle, repairing, and then dumping it back. If anything would cause HSA, that's it. And no issues on my end. Although as always YMMV. Point is, I wouldn't worry about HSA being your source. It definitely wouldn't be enough to do this much damage.

Second: Is the lid on your bucket sealing properly? If you're getting good airlock activity then you're probably ok. However, if you're not, and there's a leak, contrary to popular believe, just because CO2 is heavier than air doesn't mean it just sits atop as a blanket if the lid is open (or cracked). Oxygen will still diffuse in over time. During active fermentation this isn't an issue because enough CO2 is produce to prevent it. But after fermentation stops, it could be a problem. But again, if you're getting good airlock activity you're probably fine there.

Third: When you rack to your bottling bucket, are you using a hose long enough to reach the very bottom of your bottling bucket, or otherwise elevating the bucket to do the same? I have seen many, MANY homebrewers who just let the hose dangle and the beer freefall from the hose to the bottom, splashing and frothing away, or run down the side of the bucket. Both of these can introduce a significant amount of oxygen. The hose needs to reach the very bottom of the bucket, and even go so far as to tilt it initially so that the end of the hose is underneath the surface as soon as possible.

I started with a bottling wand that appears to have been oxidizing my beers. I'm at the end of an experiment on this, but I'm 95% sure that the large amount of agitation/foam that was kicked up by my old wand was producing oxidation in my lighter beers. But if your beer is flowing smoothly into your bottles without producing any foam or bubbling, then you can scratch this hypothesis off the list, I guess.

I'm sorry if this has been mentioned before since i haven't read all the replies but one look at the picture brought back terrible memories of when I was dealing with a similar issue. I ended up figuring out that I wasn't properly sanitizing my bottling wand. I would stick it in sanitizer but I wasn't fully disassembling it. As a result, I was getting a weird infection that would turn the beer a brown almost purple color and cause a slight harshness taste to develop during bottle conditioning.

robopp said:

I'm sorry if this has been mentioned before since i haven't read all the replies but one look at the picture brought back terrible memories of when I was dealing with a similar issue. I ended up figuring out that I wasn't properly sanitizing my bottling wand. I would stick it in sanitizer but I wasn't fully disassembling it. As a result, I was getting a weird infection that would turn the beer a brown almost purple color and cause a slight harshness taste to develop during bottle conditioning.

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That is very interesting. I too am getting a brown then into almost purple color in my beer as it ages in the bottle. The yeast at the bottom of the bottle in particular has been very purple-ish. Maybe there's a contamination somewhere.

Cold Crashing may help

Just completed my bottling experiment: https://www.homebrewtalk.com/showthread.php?t=529395

Basic conclusion in my case: probably an infection caused by something on the bottling wand or in the bottling bucket.

I think I figured it out! Knock on wood. I was brewing a funky dark saison yesterday, and taking great clear the sanitize the hell out of everything to try to rule out an infection, and for the hell of it I decided to scrub some dark marks off of my copper wort chiller (oxides?). I scrubbed it pretty good with a rough sponge, and when I was done, there was a bunch of dark, fine debris the bottom of the sink. I thought more about it, and what I typically do is just put the chiller in the boil w/5 minutes or so remaining to sanitize it. When i put it in, it is dark marks on it and is dull, when I take it out it is gleaming. Thus, all that oxide has to go somewhere and I think just was in the wort. So when I used to bottle, the oxide from the chiller would be in solution, and also would settle to the bottom of the bottle (thus explaining why the beer was much darker than it should have been and why the yeast at the bottom was blue-ish purple).

This batch is dark so I probably won't be able to tell if I fixed the problem, but my next batch will be a very pale ale (low SRM), so I will report back if that fixed the issue.

That's oxidation.... idk why you ignored the first response you got cause it was spot on.

j1n said:

That's oxidation.... idk why you ignored the first response you got cause it was spot on.

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No... I don't think that is oxidation. Oxidation is the reaction of oxygen molecules with another substance. What's happening here, if accurate, is the introduction of an already oxidized substance into the wort. NOT the introduction of, and interaction with, OXYGEN itself.

It would explain why there is a color change, but not a flavor change - because the beer itself is not oxidized. It is simply contaminated - for lack of a more benign term - with an undesired substance from the copper chiller.

McKnuckle said:

No... I don't think that is oxidation. Oxidation is the reaction of oxygen molecules with another substance. What's happening here, if accurate, is the introduction of an already oxidized substance into the wort. NOT the introduction of, and interaction with, OXYGEN itself.

It would explain why there is a color change, but not a flavor change - because the beer itself is not oxidized. It is simply contaminated - for lack of a more benign term - with an undesired substance from the copper chiller.

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Then why is the beer not dark when taking a gravity reading if its cause of the chiller?

looks to me like it got dark after he bottled it. Just cause he or someone else couldn't taste the oxidation doesn't mean that its not oxidized. Not the first time ive seen someone say it taste fine but its dark from oxidation.

Sure, no doubt about the possibility that it IS oxidized. My post was meant to clarify that scraped "oxides" from the chiller being introduced to the wort/beer is not the same as the chemical process of oxidation.

It is probably not conclusive that the chiller is the root cause; I'd not think that something so minor would be invisible until bottling and would result in a profound color change.

McKnuckle said:

Sure, no doubt about the possibility that it IS oxidized. My post was meant to clarify that scraped "oxides" from the chiller being introduced to the wort/beer is not the same as the chemical process of oxidation.

It is probably not conclusive that the chiller is the root cause; I'd not think that something so minor would be invisible until bottling and would result in a profound color change.

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Since color was fine before bottling and got dark after, it seems like the likely cause was it got oxidized when racking to the bottle bucket.

I was pointing out how he disregarded the first response when it was correct about being oxidation. The pic he posted looks exactly like all the oxidized beer ive seen. just like that post pointed out "dull brown color".

j1n said:

That's oxidation.... idk why you ignored the first response you got cause it was spot on.

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I certainly did not ignore the first post and have taken steps to reduce potential oxidation, i.e., reducing splashing while bottling. I've also taken steps to up my cleaning and sanitizing game as recommended. My last post was not meant to say that I think the beer is oxidizing (though that may be a contributing factor), I'm saying that I think copper oxide formed on the outside of the chiller during weeks or months non-use were being dissolved into the beer during the boil. Just as I had dark matter in the bottom of my sink after I scrubbed my copper chiller.

Of course oxidation (via there being too much oxygen in the wort) could be a problem as well, but I'm hoping (knock on wood again) that a primary culprit is the copper chiller.

Was the chiller the issue? I too began having this problem months ago and have tried everything I can think of (except getting a new chiller) to no avail

Note that the off flavors, color changes and instability that are caused by oxidation is a multi step process. The oxidation is a precursor for other reactions.

Ground state oxygen itself has a low reactivity and needs to be "activated" by light, enzymes or traces of metal ions and converted to superoxide, peroxide or hydroxyl before most reactions occurs. The copper added to the beer may accelerate the oxidation reactions from the DO as well as the copper oxide becoming precursors to later reactions themselves.



Cleaning the oxide off the copper manually or with an acid (such as StarSan) will help.



**Enzymic and Non-Enzymic Oxidation in the Brewhouse: Theoretical Consideration, Charles W. Bamforth, Department of Food Science Technology, University of California, Davis, CA 95616- 8598, 1st February 1999

What I'm more excited about is that tiny bottle of tarragon. Whatcha cookin?