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Off Aromas in Kegs, Not in Packaged Beer

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  • Off Aromas in Kegs, Not in Packaged Beer

    Hey guys, long-time lurker, first-time poster. Bear with me here, I've been trying to tackle this problem myself for the better part of a year and am just about out of ideas, so it's gonna be a bit of a long read...I'm at my wit's end here and am desperate for any help!

    We've been operating for about a year now and have had an occasionally-recurring issue with some of our kegged beer. A few of our styles--usually our pale ale and our stout--occasionally develop an aroma I can only describe as "rotten vegetable"; it starts off subtle and doesn't appear until after a few weeks in the keg, and I note it also dissipates a few minutes after the beer is poured. It does tend to worsen with time; I sent a sample down to White Labs after we had to dump a batch, and they suggested it was caused by an unhealthy fermentation. No infection was present. The thing is, we package more beer than we keg and it's NEVER showed up in our canned or bottled beers, even after a long time on the shelf, and I can find no differences in our fermentations (and sometimes we split batches, too, where the kegs get funky and the bottles or cans do not).

    We got all of our kegs from Gopher Kegs. They're stainless with Micro Matic valves. I've tweaked all manner of variables in our keg cleaning process--switched from caustic cleaning using Wesmar's Brew Kleen LF to using their Defy acid cleaner (on the recommendation of other local brewers). I've switched back and forth between TripleSan acid sanitizer and Purisan PAA sanitizer. We clean kegs manually in two stations--first is a hot rinse with flash-heater tap water, followed by CO2 purge, followed by recirculated acid-detergent cleaner, followed by a hot water rinse and CO2 purge. This is all done with a portable pump and a massive valve manifold. The second station involves filling the keg with sanitizer, inverting to soak, then pushing with CO2 into the next freshly-cleaned keg, then pressurizing the sanitary keg to 5 PSI and storing prior to filling. Since we don't have immersion heaters for our chemical sinks, we drain & refill with fresh hot solution every 5-10 kegs, both for cleaner and sanitizer (yes, I want a keg washer!!). None of my changes have had any effect on this issue. We have had this off aroma come out of beer kegged in brand-new kegs as well as kegs on their 2nd and 3rd fillings, too, so I don't believe it's from any kind of residue. I have pulled spears after cleaning and our kegs are spotless.

    Our keg filling procedure is to hook up 1/2-inch beer line to the bottom port on the BBT, blow out any settled solids/yeast/trub, use Micro Matic cleaning/filling heads to jumper 4 sanitary kegs together (filling into "beer out" and then pushing out "gas in" to the next keg). The last keg in the series has a blow off hose in a bucket of sani. We keep the head pressure at about 15 psi on the BBT and push the beer that way until we've filled all the kegs we need, rotating the last keg in each series to become the first keg in the next series so we're not wasting beer until the very end. None of our beers are filtered.

    One thing I have noticed is we only get this smell on beers fermented with US-05. We do not get it on any of our Belgian beers (T-58 or WB-06) or on anything we've done with S-04. We've also had the smell not show up on some other US-05 beers, like our IPA. Like I said, we don't get this smell from our canned/bottled beers fermented with US-05. I've tried switching yeast nutrients and varying wort oxygenation, but no change.

    At this point the only thing I can think is that it has something to do with spunding, since we cap our fermenters at about 7 points above TG, which usually builds up around 15 PSI at ambient temperature. We then crash gradually over 3 to 9 days depending on schedule. But like I said, we do this on all our beers and it's only a few varieties of kegged beer that develop the smell.

    So...help?? The only ideas I have left are a) switch yeasts on the problem beers, b) try a proper keg washer, c) try a few batches without spunding, or d) get a beer filter. But do any of you guys see something in my cleaning procedure? My filling procedure? Is there something that happens in kegged beer naturally that wouldn't happen in a can or bottle that could cause this? I'm going to lose my mind if I can't solve this!!

  • #2
    Originally posted by igliashon View Post
    One thing I have noticed is we only get this smell on beers fermented with US-05. We do not get it on any of our Belgian beers (T-58 or WB-06) or on anything we've done with S-04. We've also had the smell not show up on some other US-05 beers, like our IPA. Like I said, we don't get this smell from our canned/bottled beers fermented with US-05. I've tried switching yeast nutrients and varying wort oxygenation, but no change.
    So there have been a few other threads with problems from this strain - mostly phenolic bandaid ones, but still scares me a lot. There is one on the top of Process and Techniques thread talking about a "fart smell" (I'm thinking H2S) from US-05. Have you thought about changing your house yeast or at least change for a little while and see if this problem goes away?

    I agree that having this as a keg-only problem is weird. Kegging usually imparts a lot less O2 into the beer during filling. I wonder if the O2 during bottling and canning is "killing" the flavor by oxidizing whatever flavor it is. This really confuses me.
    Peter Cronin
    Senior Quality Analyst
    AleSmith Brewing Company

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    • #3
      I would try a different filling method. Something weird could be happening with jumpering the kegs together. Try a kegging manifold that fills all the kegs separately and see if it goes away.


      Sent from my iPhone using Tapatalk
      Last edited by timm; 01-26-2016, 01:18 PM.

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