[nateo]

I'm not much of a Bio guy, but I came across this on wiki: "Acetobacter can be easily distinguished in the laboratory by their growth of colonies on a medium containing about 7% ethanol, and enough calcium carbonate to render the medium partially opaque. When Acetobacter colonies form enough acetic acid from the ethanol, the calcium carbonate around the colonies dissolves, forming a very distinct clear zone."

That experiment sounds easy enough to rig up at home. I'm thinking diluting vodka to 7%, adding some calcium carbonate, and I guess sugar? Any ideas how much of those I should add?

If the gravity is dropping, does that mean that the sugars are being consumed? Acid is denser than ethanol, right? So if the bug were eating ethanol and making acid, the gravity would go up? Do acetobacter eat sugar?

[tomsawyer]

I don't think you'd notice a change in gravity before things really got going.  You'll smell vinegar long before you can measure it.  Just leave a little of your beer in a bottle with plenty of head space, in a couple of weeks it'll smell like vinegar if this is acetobacter.

[tschmidlin]

Don't add any sugar if you want to be able to distinguish it from brett.  Acetobacter just needs the ethanol to make acetic acid.

[tomsawyer]

Tom can you tell the difference between Brett, mold and/or acetobacter from looking at its growth early on?  I would assume they both start as colonies/mycoderma/"flowers".  I think the latter two are more commonly encountered than Brett.

[nateo]

Gravity is stable at 1.006 so far. Checked pH with my new calibration solutions, and the pH is 4.1.
So, maybe Lennie is right and it's just mold?

[tschmidlin]

Tom can you tell the difference between Brett, mold and/or acetobacter from looking at its growth early on?  I would assume they both start as colonies/mycoderma/"flowers".  I think the latter two are more commonly encountered than Brett.

I'm not sure - my acetic jar doesn't have anything on top that has looked remotely like a brett pellicle at any point.  It actually looks kind of oily on top with a thin brittle film, nothing furry.  There is no visible gelatinous mother.  I started the jar with raw vinegar from the store though, not with something sold as a "mother culture".  And since it is a wine vinegar jar, the difference in media alone could cause a difference in appearance.  That is the only thing I have with straight acetobacter, everything else with acetobacter is a blend.

<edit> But my original point was that if you were going to base your analysis on the clarity due to the CaCO3 buffering the acid production and the media clearing, better leave out the sugar.

[tomsawyer]

I looked in my own vinegar mini-barrel and theres stuff growng on top but I'm not sure its acetobacter.

[bluesman]

If it's tasting good, I would just drink it all now, quickly.  I love a good funky beer, but unless you feel like risking the batch it's best to just drink it.  Save the gallon jug and see how that part of it goes over time, if it is still good then you got lucky and you can use that jug to dose another beer intentionally.

+1

I tend to agree.  Drink the 5 gal batch now and let the 1 gal batch go as an experiment and/or potential future use.

[nateo]

I filled a champagne bottle with half the infected beer and half a portion of grapefruit mead that turned out not-so-great. The results were surprisingly great beer. I carbed it to about 5 volumes. The mold (or whatever) has stopped doing whatever it was doing, and the gravity has been stable at 1.006 (I think, but I'll doublecheck when I bottle the rest).

So I dunno. There's a moral in there somewhere.

[tomsawyer]

Two wrongs sometimes do make a right?

Glad to hear its salvageable in some form or fashion.  I made grapefruit wine once, I liked it but nobody else did.  Come to think of it my first batch got an infection and I kind of liked the funk and fruit.

[nateo]

My wife said it's one of the best beers I've made. I don't know if that's a compliment or an insult. She did drink it really quickly, so I guess compliment? 

[tschmidlin]

My wife said it's one of the best beers I've made. I don't know if that's a compliment or an insult. She did drink it really quickly, so I guess compliment? 

Take it

[nateo]

I've not been able to get rid of my "mold" or whatever from that one plastic bucket, so I've been using it exclusively for my sour/funky beers. The pellicle recently formed on a no-boil Berliner Weisse, which is interesting since the pH is currently 3.1. I had assumed that would be too low for the mold, but I guess if StarSan won't kill it, it's probably low-pH tolerant. If it's gonna stick around, I think I should give my new pet mold a name. Any suggestions?