06/27/10 07:12 PM
Sour Beers and Draft Lines
This is not a thread about preventing infections in draft lines. It is based on an observation I have made with 4 different sour beers, 3 of which I have observed repeatedly.
I first remember noticing on a trip to Trinity Brewing in Colorado Springs. I ordered a La Folie on draft, and when I was first drinking it, it was metallic and nearly unpalatable. Within 5 minutes, whatever it was gassed off or went away and it was a glorious glass of the beer.
At Golden City Brewery, I would taste our Gose, and at first, get the same sort of metallic, almost oxidized flavor, very unappealing, and then within 5 minutes, it was completely gone and the beer was tasty as it should be.
At Yak and Yeti, my berliner weisse, if the beer has been sitting still in the lines for a bit, for example over night, the first pours off of it, I will get the metallic flavor, and then within a few minutes, gone completely and tasty as hell.
At home, my berliner weisse, if the beer has been sitting in the lines, it will be metallic, and after a few minutes, normal.
If I clear the lines at the Yak or at home, the beer will taste normal immediately. I have only ever noticed this flavor with sour beers. The lines are cleaned regularly, and it has no other off flavors. Inevitably, the beer will become what it should be within minutes, and it seems like it sitting in the lines is a necessary prerequisite to the taste occurring.
Does anybody have any clues as to what could be causing this?
For what it's worth, my fiance noticed the taste in the La Folie, but I don't think I have given her any of the others to taste when I taste it. Jeff, the head brewer at Golden City, didn't taste the metal in the Gose whenever I would point it out.
I would say that it might be in my head, but it isn't consistently there with my Berliners at the Yak and at home, it is only when the beer has been stagnant in the lines. It is easy enough to dump the ounce or two at home, but at work my lines hold 32oz or so, so it is a slightly bigger issue.
06/29/10 07:17 PM
Re: Sour Beers and Draft Lines
It sounds to me to be tetrahydropyridines.. heres and excerpt I wrote recently: "Two forms of substituted tetrahydropyridines, 2-ethyltetrahydropyridine (ETHP) and 2-acetyl-3,4,5,6-tetrahydropyridine (ATHP), can be produced by Brettanomyces spp. in the presence of the amino acid L-Lysine and ethanol with oxygen having a stimulatory effect in their formation (Heresztyn, 1986a; Snowdon et al., 2006; Oelofse et al., 2008). The aromas associated with ATHP are similar to cracker biscuit or popcorn, although under low pH conditions can be described as metallic or bitter (Oelofse et al., 2008). Little is know about these compounds and their production by Brettanomyces spp."
There is a third tetrahydropyridine formed by lactobacillus along with the other two so its not just formed by Brettanomyces... My guess is maybe its being produced while sitting in the line as oxygen will clearly be present even in minute but sufficient amounts... Then the only explanation is these compounds are volatile enough that after letting the beer "breathe" they are not noticeable... I'm not convinced but its an idea I had.. If you want to read more.. well there is no information but look up mouse taint in wines...
Any Gose left at GCB?
06/29/10 08:32 PM
Re: Sour Beers and Draft Lines
Mouse taint? Hmmmm.
That sounds insanely complicated and makes my head hurt. I am going to go ahead and say, yeah, that must be it.
Last year's gose is gone, but we are brewing it again before GABF, so it will probably be brewed sometime in July. I can't wait.