Acetobacter Infection From Bottle Dregs?

I would worry more about minimizing exposure to oxygen. Having a relatively impermeable fermentor and keeping sampling to a minimum. I like at least a touch of vinegar so I use an airlock but you could move to a solid stopper after primary fermentation is done.

 

Agreed, although moving to a solid stopper is risky that early. This is especially true if you aren't using a barrel. The Brett can release quite a bit of CO2 over the course of secondary fermentation. The one time I tried it (venting weekly) in a plastic carboy my lambic got very sulfury. After switching back to an airlock, it eventually volatilized.

 

I've got two beers coming on a year ( finally!! ), that have some dregs.. One has more acetic notes than the other.

I did however, add some dregs from beers that were all barrel aged and did have an acetic background on them in the bottles, so I wasn't surprised to see it transfer to the carboys.



I think you'd be okay, but as with sours and spontaneous.. it's not always up to you.

 

As others have stated, the issue will be O2 exposure during the aging process. Even if there is no acetobacter in the mix, Brett can produce acetic acid in the presence of oxygen. It can also convert it to ethyl acetate, which is fruity and nice, but too much and you end up with nail polish remover. A big key is to use a fermentor that is as impermeable to O2 as possible, and stay out of it as much as possible.

 

I remember reading that on your blog. Out of curiosity, have you started drinking the Drie Fonteinen dreg lambic yet, I've been following that with interest and I think you bottled it quite a while ago.

 

By far my best lambic to date. Sending a bottle to NHC, we'll see if the judges in Philly agree.

 

No issues with dregs here. I have a lambic in a glass carboy that is 2 years old now, and I pull a small sample every few months and it has absolutely no acetic character.

I did a flanders red (using roeselare) in a bucket, though, that after a year with regular 2-3month checks became VERY acetic. Like, it would be good on a salad, or for drinking if you like a face ripping vinegary-flanders.

 

I'm actually surprised there isn't any acetobacter in the Roeselare blend. Don't you need some acetic character for a true Flanders red?

 

Roeselare has four microbes capable of producing acetic acid.

 

I assume all four of these microbes require oxygen to produce acetic acid, so I think this confirms the earlier advice that the key factor is not avoiding acetobacter, but rather avoiding oxygen exposure.

 

Two of the four don't require any oxygen to make acetic acid. The other two will make less acetic acid in anaerobic conditions. If the goal is to produce a sour beer without too much acetic acid, then keep the lid on and don't open it for at least six months. It's OK to use a bucket. If you keep the lid on for at least six months, it won't make a vinegar bomb.

All sour beers have acetic acid.

 

So implicit in what you are saying is that lactobacillus makes acetic acid? Or saccharomyces does? This is news to me.

 

Lactobacillus, pediococcus, brett L and brett B can make acetic acid.

 

Hmmmm, interesting. I do suspect, though, that Rodenbach Grand Cru relies on acetobacter, and not something like lactobacillus, for its acetic acid character.

 

What makes you say that?

 

So, aside from brewing beer, I also make homemade yogurt. I've made several dozen batches, and the lactobacillus bugs have never produced enough acetic acid for me to notice it. I'm not saying they're not producing acetic acid - maybe they are - but my yogurt does not have anything approaching the level of acetic acid character that Rodenbach Grand Cru does. And the same goes for the Berliner weisse beer I made, and the gose I made. And every commercial Berliner weisse beer or gose I've ever bought.

So I very much doubt that Rodenbach Grand Cru is getting its acetic acid character from lactobacillus. I suppose it's possible that the brett strains produce enough to give it that slightly vinegar-y kick, but again it seems doubtful to me based on brett beers I've had.

At the end of the day I can't prove that Rodenbach Grand Cru has acetobacter in it, but I would bet a lot of money on it.

 

I don't find Gran Cru to be anything beyond slightly sour and mildly acetic. Compared to many American sours in the Flanders-esque style, it's a weak sauce sour beer.

Your yogurt, Berlinners and Gose definitely contain acetic acid, but not to the point where you taste an off putting vinegar note. Berlinners and Gose are low abv. The amount of acetic acid produced in a low abv beer will be a lot less than a bigger sour beer. Cascade ferments with lacto brevis and they don't pitch brett. They are blazingly sour, big beers that have a big acetic note that no one seems to mention or complain about while rating it a 4.5.

Without a doubt, Gran Cru gets some acetic acid from lactobacillus. If it contained no lacto, perhaps you wouldn't consider it vinegary? Acetobacter is also in the mix, but they don't pitch a fresh, lab prepared culture of acetobacter. It migrates through the air into the barrels and it's part of the barrels. The barrels are treated in a manner to minimize acetobacter. Basically, acetobacter is something sour barrel breweries try to minimize.

Your assertion that Gran Cru is an excessively acetic beer primarily because of acetobacter made no sense to me originally and it makes less sense now, but I understand how you arrived at such a conclusion. You think Gran Cru is excessively acetic and gets most of its acetic acid from acetobacter based on your experience with yogurt and Berlinner Weisse beers.

 

I don't know so this is just a curious question, but why do you believe that each of lacto, pedo, brett and sach all produce acetic acid on their own? At some point with exposure to oxygen, it seems that any fermenting product would become subject to noticeable acetic acid production from acetobacter to some degree.

 

To be clear, I love Rodenbach Grand Cru and don't consider it excessively acetic. I just detect a lot more acetic character in Flemish Reds than I do in just about any other style (more so in Grand Cru than in regular Rodenbach, though). I had always assumed this was because of acetobacter, but I concede I could be wrong. It just seems odd to me to pin the acetic character on lactobacillus when acetobacter seems like the more likely culprit.