A strange off-flavour I've never encountered before

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Beeru

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Hello,

So, I've scoured the internet for explanations of off-flavours in home brew, and I have two beers on tap right now that have both developed a flavour at the same time, and I can't figure out why. Actually, its not really a flavour, but a smell, but it's hard or impossible to differentiate the two.

The smell is basically just maltiness, but the kind of malt / brewing smell you get when you walk past an industrial brewery. It's quite intense. It showed up in two beers that were kegged roughly 6 weeks ago, an IPA (three floyds zombie dust clone) and a Pale Ale (In The Pines West Coast Pale Ale). It was not present at the time of kegging or for the first month of drinking them. There can't be any leaks in the keg letting oxygen in, or I would have run out of C02 ages ago, and that's the only factor that I could think of. It's strange that it's happened to two beers at the same time, but it hasn't happened to the other three beers on tap, which were brewed with grains and hops that were purchased at the same time (so I don't think it has to do with the age of either).

Does anyone have any thoughts? Maybe I'm just classifying the off-flavour incorrectly and this is a common problem that I've misdiagnosed? A couple of friends noticed the smell independently though, and also described it as that malty smell of a brewery in full operation.
 

BrewZer

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Makes me wonder about common ingredients in both beers... same batch of base grain? Same yeast?

Sanitation comes next... did you clean the valves & o-rings after the last batch? StarSan getting cloudy? Tubing getting old?

Temperature control... fermenting at the same or uncontrolled temps? Serving temp... is your kegerator working right?
 
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Beeru

Beeru

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Makes me wonder about common ingredients in both beers... same batch of base grain? Same yeast?

Sanitation comes next... did you clean the valves & o-rings after the last batch? StarSan getting cloudy? Tubing getting old?

Temperature control... fermenting at the same or uncontrolled temps? Serving temp... is your kegerator working right?
All good questions.

They do have the same base grain, however so do two of the other beers on tap that don't have the same smell (a stout, and a pilsner. There's also a braggot on tap that used some of the same grains, but far less).

They have different yeasts, one was a wyeast (denny's fav) and the other Saf05. They did ferment at the same time (I made them just one day apart) so that could be a factor, although I've never heard of this particular smell happening only after 6 weeks in the keg due to fermentation temp.

Kegerator is working right. It sits between 2-4c. I just tested to make sure the temp controller is accurate, and it seems to be.

And I did the same procedure that I always do for cleaning. I first clean the keg with either starsans or PBW depending how how much grime is in there, then rinse, then put in some no-rinse cleaner, and run that through the lines in the kegerator until its all purged. It's possible something contaminated both batches, since I did keg them at the same time. But what would wait 6 weeks to create the smell of malt?
 
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Beeru

Beeru

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Have you opened either of these kegs and taken a look inside yet?

Cheers!
I hadn't. I just had a look and while it's difficult to see in there, I didn't see anything out of the normal. There no molds or things growing in there. Not sure what else I'd be looking for.
 

Vale71

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Sounds a lot like diacetyl. It's common for it to develop (either from the precursor or through an infection) some time after packaging. I would take a good hard look at your fermentation practices.
 
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Beeru

Beeru

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Sounds a lot like diacetyl. It's common for it to develop (either from the precursor or through an infection) some time after packaging. I would take a good hard look at your fermentation practices.
Interesting. Can Diacetyl commonly show up in this way? I haven’t heard it described this way. The yeasts were a little older. Still within their 'best before' date, so maybe it does have something to do with that. They seemed to ferment fine, and they both had a couple weeks in the carboy to condition after the primary fermentation. But maybe the yeast wasn't strong enough to consume that diacetyl.
 
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seatazzz

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Asking for clarification; is the smell only present when you pull a pint, or from the tap itself? Like, when you walk past the kegerator and happen to sniff, you smell it? That sounds to me, like spillage that wasn't noticed. It will start to smell malty as the liquid evaporates away. Wait a bit longer and it will smell nasty. Speaking from a "friend's" experience (yeah I know it was me but i have to make myself look good here).
 

Beermeister32

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Check your regulator and C02 lines. If it is common to two separate batches hooked up to the same C02 lines, that might be the issue, funk or other weirdness in the regulator or lines finding its way into both kegs.
 

MicroMickey

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It the smell distasteful? If it smells like an industrial brewery in full operation, perhaps you should wonder why your other beers don't smell this way too.
 
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Beeru

Beeru

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Asking for clarification; is the smell only present when you pull a pint, or from the tap itself? Like, when you walk past the kegerator and happen to sniff, you smell it? That sounds to me, like spillage that wasn't noticed. It will start to smell malty as the liquid evaporates away. Wait a bit longer and it will smell nasty. Speaking from a "friend's" experience (yeah I know it was me but i have to make myself look good here).
I don’t smell it from the taps right now, however the smell has dissipated in the beer quite a bit now, a few days later, and if it is just spillage i suppose it would make sense that after a number of pints were pulled and a few days past the smell would go. Perhaps that’s all it is.
 
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Beeru

Beeru

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It the smell distasteful? If it smells like an industrial brewery in full operation, perhaps you should wonder why your other beers don't smell this way too.
The smell isn’t so off putting that I won’t drink it, but it’s not nice. it’s just odd. I do wonder why it’s just these two and not the others.
 
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