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Metallic or stale flavor develops with time

Northern Brewer General
#1

I haven’t posted on here in a little while, and in the meantime, have made quite a few delicious brews. But something is once again bothering me, and I’d like to solve it once and for all.
I’ve noticed that my beers, after sitting in bottles for a few months, all evolve to a similar “stale” flavor. It’s a bit metallic, and all the delicious hops and beer flavors become muted. Sometimes this happens in one month, sometimes in three, but it’s inevitable. One solution is drink the beer quickly, of course, but that I’d like to solve it. Here are some thoughts:

  1. My water report indicates that my water is very soft, and has very little chlorine, so I don’t think it’s a water problem. However, I could be wrong about that!

  2. Maybe a bottle sanitation problem, and the “metallic” flavor is a red herring. I wash my bottles with 1-step using a vinator pump. I’ve never had any real gushers or other nasty “infected” tastes. I have not tried aging a keg, so I can’t comment on that end.

  3. I use freshly milled grains in all-grain. So not stale ingredients. I have excellent conversion, so something is right with the water chemistry.

  4. Maybe oxidation, so I try to limit splashing. I bought oxygen barrier caps recently, but can’t comment yet on if they help.

Any of your thoughts would be awesome!
Thanks!

#2

Not sure of metallic flavors, but removing the chlorine and not using One Step as a sanitizer will be a good place to start.

When grains come into contact with choline or chlorimine, chlorophenols are formed creating off flavors. Using Campden tablets in you water will remove these.
Do not use One-Step as a no rinse cleaner/sanitizer. I always used to pick up off flavors with this product when I used it. Rinse thoroughly and use a sanitizer such as Star San.

#3

Those two off flavors are characteristics of oxidation. i’ve fought that myself, made changes to water and tried various ingredients. Now I’m focusing on oxidation. When I ferment in a bucket I’ll transfer to secondary carboy when the bubbling starts to subside, making sure I transfer plenty of the yeast cake so things don’t stall. Also trying stuff like conicals and counter-pressure transfer.

I don’t have problems with hoppy beers, maybe the hop oils protect from oxidation to some extent. My brown beers like dubbel, brown, etc are the ones that show this metallic flavor. I’m getting better flavor so far with my anti-oxidation campaign, although I don’t have a lot of batches done yet so I’m not positive this is the only factor.

#4

Thanks for those thoughts. When using one-step, did you pick up those off-flavors immediately? Or did they develop? Perhaps there’s something in the chemistry of one-step that makes them develop.

As for oxidation, I’m thinking the same thing. Although, I was under the impression that homebrewers don’t need to worry too much about oxidation. Maybe I’ll try to minimize the time my beers stay in plastic buckets. I got rid of my glass carboy (too many horror stories of shattering and ER visits), and bought a Better Bottle, but I have only one of those.

I, too, have noticed that the darker beers develop that flavor faster. I have an oatmeal stout that was my most delicious beer yet when it was fresh, 10 days in the bottles. Now it’s turned like the rest (after about 4 weeks) … super sad really, but good thing there are only a few left!

#5

Its also possible that its coming from warm ferm temps. Sometimes the esters and fusels you get from high temp ferms can taste metallic from a bit of acid.

#6

are you treating your water for chlorine? if not thats probably the issue

#7

As tom said, this is classic oxidation. Ever get an imported German beer in the bottle? It’s the same flavor, metallic or wet cardboard, from the months of transport and sitting on the shelf. To minimize the effects, the biggest thing you can do is store all your bottles cold once they are carbonated. Temperature has an enormous effect, and every 10°C you can decrease the temp roughly slows the staling process by a factor of 3. For instance, if a beer stales in 1 month at 25C, it will take 3 at 15C, and 9 at 5C.

Other than cold storage, you can minimize exposure of the beer to oxygen post fermentation. This means purging the receiving vessels before filling, minimizing splashing, etc. However this is a small effect when compared with storage temp, and all beer will eventually stale no matter how well you do with keeping O2 out.

edit: I’d like to add that I noticed some minor oxidation in my bottled beers when they hit the 3 month mark, and excessive staling at the 6 month mark when stored at room temp (~65-75°F). I haven’t bottled anything in a couple of years now, but that was my benchmark from 4 batches of lager that were all made concurrently. It seemed to vary a bit by recipe, and I’ve read that beers with some roasted malt in the grist tend to hold up better over time. Really my sample size is too small to evaluate that.

#8

Thanks a lot for the thoughts!
I’d better bottle my IBA and pop all my beer in my extra fridge then. I thought, since it’s winter and the pantry is pretty cool, that should be okay. But can’t be too safe.

As for purging, if lagering, should I be sure to replace the top gas with CO2, or will residual fermentation do that for me? And when bottling, do I push a little gas in the bottle before filling, with the bottle upright? then fill and cap as normal? I’ve never done any purging…

#9

To minimize oxygen ingress, it’s best to minimize transfers as much as possible, and keep the beer in a vessel with low O2 permiability (like glass or a BB). The “CO2 blanket” theory is generally right when you have active fermentation and positive pressure in the fermenter, but once fermentation is over any air that gets into the fermenter will eventually mix and be exposed to the beer. So to minimize exposure if you want to transfer to a secondary, for instance, shoot some CO2 in the carboy or keg before you fill with beer. The CO2 should displace any air that’s already in the vessel for a short time (eventually air will diffuse in and eliminate the purge unless there is a physical barrier).

For bottles, people usually use devices designed for filling from kegs that have a button for shooting some CO2 in the bottle before filling (e.g. Blichmann beer gun, counterpressure fillers). However some believe that a small amount of O2 will be consumed by the yeast during bottle conditioning, so it’s unknown how effective or necessary the above techniques are. I don’t ever bother with all this stuff since I’m happy with the shelf life that I get out of the current process, and anything that I need to keep for > 6 months goes in the fridge.

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