Kettle sour infection question

[millsbrew]

So my kettle sour is clearly infected with some form of yeast. Must have come from my lacto starter because I did a 30 min boil to fix a low gravity issue.

View attachment ImageUploadedByHome Brew1505594326.220864.jpg

Gravity was 1.039 and pH was 3.99. Now it's 1.014 and pH is 3.13.

The taste is actually kind of bland with a slight tang. So I was thinking about boiling for 45 mins and adding some DME. Any other thoughts/suggestions about what I could do?

Thanks.

 

[Grod1]

your plan sounds good to me./ add some fruit juice?

 

[jfolks]

I wouldn't boil it. I'd add some fruit and maybe some Brett.

 

[Mashinations]

I might be missing something here - but if you boil it, you're going to boil off all the alcohol in it.

 

[RPh_Guy]

He needs to boil it if he doesn't want his bottling equipment/kegs to come into contact with live bacteria. Boiling as short as possible should leave enough alcohol.

If this were mine I would let it ferment to completion, and then bring to a boil just to sterilize. Add some hops if you want. I wouldn't add anything else.
At that pH it will be quite sour.
If you add more DME you'll have a significantly higher final gravity. The sweetness/malty flavors will probably overpower the sourness if I had to guess.

Chalk it up as a learning experience. Maybe the beer will be ok when it's done.

 

[MizzouFermentationScience]

Had the exact same thing happen to me recently. My initial gravity was higher- 1.050 and I pitched with a handful of grain right after sparge and left it outside for a few days. I wanted to boil as well but it didn't get sour enough before fermentation really kicked in (I didn't plan well so no starter). I proceeded to rack it at ~1.02 and add some dry hops to stop the lacto. It finished ferm within a couple of days and did not get more sour- in fact what I took away from it was to overshoot the sourness when tasting fermenting wort. Cold crashed then kegged and the beer was delicious. If kegging is an option, don't boil. For bottling, try hops, sulfur dioxide, and/or lysozyme to avoid boiling at this stage.

 

[specharka]

He needs to boil it if he doesn't want his bottling equipment/kegs to come into contact with live bacteria. Boiling as short as possible should leave enough alcohol.

If this were mine I would let it ferment to completion, and then bring to a boil just to sterilize. Add some hops if you want. I wouldn't add anything else.
At that pH it will be quite sour.
If you add more DME you'll have a significantly higher final gravity. The sweetness/malty flavors will probably overpower the sourness if I had to guess.

Chalk it up as a learning experience. Maybe the beer will be ok when it's done.

Flash pasteurization occurs around 160F, and you can pasteurize wort for 20 minutes @ 145F, which should preserve much of the malt flavor. Which is great, because alcohol evaporates around 170F, meaning you couldn't achieve a boil without making NA beer.

Just let it finish and rack to some fruit with Brett. Your taste buds will thank you.

 

[RPh_Guy]

Flash pasteurization occurs around 160F, and you can pasteurize wort for 20 minutes @ 145F, which should preserve much of the malt flavor. Which is great, because alcohol evaporates around 170F, meaning you couldn't achieve a boil without making NA beer.

Pasteurization is meant to kill *most* of the bacteria. Sterilization by boiling kills *all* the bacteria. They are not interchangeable.

As a common example, pasteurized milk goes sour over time because there are still small amounts of live bacteria after pasteurization.

Especially in this case where he has wild bugs, I'd be more cautious about contaminating cold-side equipment. One of the main ideas supporting the kettle sour method is that it doesn't contaminate your equipment ... with bacteria or Brett.

Cheers

 

[MizzouFermentationScience]

Flash pasteurization occurs around 160F, and you can pasteurize wort for 20 minutes @ 145F, which should preserve much of the malt flavor. Which is great, because alcohol evaporates around 170F, meaning you couldn't achieve a boil without making NA beer.

That's not how this works. Partial vapor pressures. Heating to 145 or 160 in an open system will result in booze lost; my gut feeling guess is a significant amount.

 

[MizzouFermentationScience]

Pasteurization is meant to kill *most* of the bacteria. Sterilization by boiling kills *all* the bacteria. They are not interchangeable.

As a common example, pasteurized milk goes sour over time because there are still small amounts of live bacteria after pasteurization.

Especially in this case where he has wild bugs, I'd be more cautious about contaminating cold-side equipment. One of the main ideas supporting the kettle sour method is that it doesn't contaminate your equipment ... with bacteria or Brett.

Cheers

Unless you are brewing inside an autoclave, we can consider sterilization and pastuerization the same thing. Things are sterilized inside sealed containers; a kettle on your back porch will never be a sterile process. Furthermore, I wouldn't worry about bugs on the cold side equipment for any reason other than changing the beer post bottling. LABs are ubiquitous; if you've ever had a little wort/beer residue on your equipment, it has hosted LAB. If you have never left a single spec of residue on your equipment, why are you worried about cleaning a sour beer up as thouroughly?

 

[asparker]

You do appear to have some kind of krausen going on so yeast is a strong possibility but a number of different lacto strains can produce ethanol and significantly drop gravity points as well. This would also create foam on top of the fermentation. I had a wheat drop about 40 points in under 3 days after I tossed a handful of malt into it.

Were you originally planning to boil it even before this happened? If not, I wouldn't change anything now.

If I were you though, I'd follow jfolks and just let it go maybe adding a hearty brewer's yeast to finish it off or some brett. If you're worried about contamination, a new bottling wand and some hose you can use just for the sours isn't too expensive. I for one like to leave my sours alive. They get so much more complex over time and you get all those probiotic benefits!

 

[millsbrew]

I ended up doing a short boil (20 mins) for a few reasons. First and foremost was to protect my hoses and chiller. Secondly, though unlikely, I wasn't even sure if alcohol production had occurred since it could have been lacto fermentation so I figured killing it was important. Lastly, I wanted to add some hops since it tasted like lemon water at that point.

I appreciate all the feedback, and I'm chalking this up to a loss. Hopefully the Brett, DME, and hops save it but I will probably dump it down the drain in 3 months.

 

[RPh_Guy]

Unless you are brewing inside an autoclave, we can consider sterilization and pastuerization the same thing. Things are sterilized inside sealed containers; a kettle on your back porch will never be a sterile process. Furthermore, I wouldn't worry about bugs on the cold side equipment for any reason other than changing the beer post bottling. LABs are ubiquitous; if you've ever had a little wort/beer residue on your equipment, it has hosted LAB. If you have never left a single spec of residue on your equipment, why are you worried about cleaning a sour beer up as thouroughly?

I agree, if you're leaving residue and bacteria on your equipment then sterilizing the wort isn't your main concern

Bottom line is that when infections happen the bugs came from somewhere. If it came from the air then oh well. But if it came from physical contact with your equipment you probably could have done something to prevent it.

Changing the beer post-bottling from wild bugs IS what we want to prevent... & from my understanding Brett contamination can be a big problem due to high attenuation making bombs.

Some people don't worry about wild bugs, and that's fine. You can get some amazing sours. The problem is that you might not get consistent and reproducible results.

@asparker
Gravity drop indicates a yeast fermentation producing alcohol. The grain you tossed in must have had wild yeast on it. Heterofermenting LAB will inhibit themselves by their acid production long before causing a big drop in gravity.

 

[asparker]

@asparker
Gravity drop indicates a yeast fermentation producing alcohol. The grain you tossed in must have had wild yeast on it. Heterofermenting LAB will inhibit themselves by their acid production long before causing a big drop in gravity.

Yeah, I thought about that too but I didn't notice any signs of regular yeast fermentation. I suppose a wild yeast fermentation doesn't necessarily have to look the same as a controlled saccharomyces cerevisiae though, does it? The OPs photo, on the other hand, does look a fair bit like a yeast ferment...

Also, and I don't mean to hijack the thread, but I was under the impression that some of those lacto bacteria could get pretty sour before they conked out though I don't can't recall where I got that from. And I assumed (perhaps wrongly) that the alcohol produced by the heterofermenting bacteria limited the lactic acid production to some extent. Do you happen to know a good source of information on this? I'd like to learn more.

I've not used grains to culture bacteria for a few years now because I could never get consistent results and there just seem to be too many uncontrollable variables.

 

[RPh_Guy]

As far as I know the MilkTheFunk wiki is the largest repository on practical information related to brewing with bacteria.

Finding more scientific information may be a difficult task. Funding doesn't exist for studies to thoroughly describe the metabolic pathways of 180+ different known species of Lactobacillus.... And I am unaware of any source that presents such information to people without advanced biochemistry knowledge. Biochemistry and microbiology textbooks would be a good starting point to really understand what's going on with these organisms.

I do have a modest professional understanding organic chemistry, microbiology, and biochemistry, so I feel confident reading these sorts of articles and expressing my thoughts.

From what I can gather the bulk of carbon utilization from all LAB species goes toward lactic acid production (even in facultatively heterofermentative species). Ethanol production in hetero- species drops off steeply as pH drops, so pre-acidified wort would likely lend toward extremely limited ethanol production regardless of species. As pH continues to drop... down to around 3.5 to 3.0 metabolism (and thus fermentation and proliferation) will effectively stop. Unless there's some intentional buffering, pH drops rather quickly with regard to amount of sugar consumed... The LAB probably consume about 1/100th to 1/1000th of the sugar before reaching inhibitory concentrations of lactic acid by-product if my calculations are correct.
These factors help explain why LAB cannot fully attenuate a beer under normal conditions.

I hope this helps a little.

 

[asparker]

Very useful and makes complete sense. I've never actually used a commercial hetero strain, so it's like that a number of the batches I used to do which dropped significant gravity numbers were actually contaminated with wild yeast without my knowing. I've made multi-generational starters to try to avoid this and to attempt to isolate tastier strains but maybe it was all for naught. Another reason to stick with commercial strains unless you really want to experiment.

Thanks for the info!