Acetobacter infection...or not?

Oxygen ingress would really increase the acetobacter quality in a sour. What has your 2 year old sour stout been conditioning in over this course of time? What did you ferment it with? I assume bugs since you are calling it a sour stout and have waited 2 years to try it.... If so, why would you worry about an "acetobacter infection" so to speak?

Acetobacter, given enough time, will straight up turn the beer into an undrinkable vinegar bomb. If it was due to infection early on (via fruit flies or something), it would only take months to get to that point rather than years. Seems like you haven't sampled your 2 year old beer at all yet, so you wouldn't really know if its an early acetobacter infection or not. You'll just have to taste it now and determine whether its straight vinegar, a sour beer with a good amount of naturally occurring vinegar, or little to no vinegar.

 

if it was pretty tart at 18 months I don't think it has a standard aceto infection. Sounds like a normal sour beer that may have some naturally occuring aceto. what did you ferment it with?

again it's all about what type of sour quality the beer has. tart doesn't usually = aceto. vinegar does. a little vinegar to a good amount of vinegar mixed in with non-vinegar sourness and/or tartness, I'd consider normal for a sour beer of that age. All vinegar I'd consider to be either an early on aceto infection (due to improper sanitation techniques or fruit flies) that decimated the beer within months, or you had lots of oxygen ingress issues over 2 years time that allowed the aceto to gradually develop to the point of decimating the beer over 2 years.

 

go buy a bottle of vinegar at the market and drink a pint of it. If you like it, then it's a palate thing

again what it boils down to is whether your sour beer is only vinegar at this point or not. if it suffered from an early on, undesired aceto infection due to sanitation issues, then 2 years is way more time than needed to completely render your beer into only vinegar. It would have only taken weeks to a month or two. Check out Oldsock's vinegar making experiment here and notice he mentions "weeks" to produce malt vinegar from beer via using an aceto "mother" which surely speeds the process up a bit..

http://www.themadfermentationist.com/2010/02/making-maltbeer-vinegar.html

if there is non-vinegar sourness, tartness, any remaining malt flavor, etc. still in "the mix" at the 2 year point, then I'd say your beer didn't suffer from an undesired aceto infection early on. the level of aceto in "the mix" would be more likely due to the bug mixes natural potential for aceto production coupled with the amount of oxygen ingress in your fermenter which allowed the bugs to convert ethanol into the acetic acid.

 

Would you hurry up and try the damn beer, now you've got me curious

 

there isn't one in every bottle of vinegar so I'd assume it isn't guaranteed.

 

Yes, please. This thread has gone on way too long without a report of what it tastes like now. I can understand some trepidation, but there's nothing for it but to try it and see what have you got.

 

It sounds like you don't like it as-is. It also sounds like you don't want to continue with the direction it is taking.

Assuming the above, you might be able to blend it with a clean-fermented stout (or other style) to mellow it out a bit, which could be done in bulk or after kegging/bottling, in the glass. Either way, packaging it ASAP would slow down whatever it is doing. You could also take a more drastic measure and kill the bugs in there with some Campden tablets.

I had Tart of Darkness, a sour stout, last year and absolutely loved that beer. It was quite sour, but the flavor still really worked for me. Is it possible it might grow on you a bit after it is carbed up?

 

If it tastes like Rodenbach then you have some aceto in there, to me that's what defines rodenbach. If it tastes good and is drinkable, then it is probably at an acceptable level, but it could keep developing.

 

Next time either find a way to reduce oxygen ingress or don't age it for so long. Seeing a pellicle is evidence of oxygen ingress FWIW.

 

Just stick some gas line hose into starsan to sanitize, attach it to a co2 tank regulator, then run it into the sanitized carboy all the way to the bottom. Turn the gas on at about 3-5 psi and let it run for a few minutes. The co2 should push most (if not all) of the oxygen out of the carboy. Then rack your beer into your co2 flushed carboy. Also make sure you are topping off your airlock as often as needed throughout your conditioning period. If you happen to use those "carboy caps" go buy an appropriately sided hose clamp and tighten it around the cap since, in my experience, they generally do not provide an airtight seal.

 

I dropped the coin and got myself two co2 setups. One 5# tank with a single regulator that goes to a three way gas distributor inside of the kegerator. The other is a 20# tank with a double regulator and a Y on one of them allowing for three lines to run off of it. I use the 20# tank for everything other than pushing beer through the kegerator. Sometimes if I'm running multiple cornies in my kegerator that require different co2 pressures, I swap the double regulator on my 20# tank over to my 5# kegerator tank. It's nice being able to pour properly (highly) carbonated wheat beers and (low to mid carbonated) porters at the same time.