Info on Sour Mash, Oxygen, and E Coli.

jivex5k · Jul 24, 2014

Interesting thread over on HBT. Kind of contradicts what I thought about oxygen's impact on the mash since common knowledge seems to be that it leads to vomit aromas.

There is a lot of mis-information out there about sour mashing, including the impact of oxygen.

When sour mashing you are actually doing two things: 1) you're creating conditions under which lactobacilli will rapidly sour the wort, and 2) you're trying to create conditions which impair the activity of other microorganisms such as enterobacteria and acetobacter.

The major factor determining the activity of lactobacilli is the temperature - lacto works best in the range of 37-42C (~98-108F), but can produce lactic acid less efficiently at much lower temperatures (as cool as 15C/60F). Lactobacillus is a microareophile, meaning it needs small amounts of oxygen, but they also don't care if lots of oxygen is present. There is anecdotal evidence that "extra" oxygen may actually lead lacto to produce a nicer flavour profile that is more complex, which has been my experience as well.

The reason we like to aim for the higher end of lacto's temperature range is that those temperatures inhibit (note: inhibit, not kill) several bacteria that can produce some very unpleasant off flavours and aromas. Enterobacteria like Clostridium butyricum will grow in a too-cool mash (at or below 37C/98F), and produce a lot of buteric acid which can really ruin a beer. Other entero's like Escherichia coli can also grow, generate all kinds of nasty off-flavours/aroma (vomit, faeces), and can be potentially pathogenic if you're doing a no-boil. All of those entero's don't give a rats behind if there is oxygen present or not - they grow fine with or without it.

The only reason people use an oxygen barrier is for Aceotobacter, which produces acetic acid (vinegar) in the presence of oxygen. In small amounts acetic acid can be quite nice in a sour, but it doesn't take much before it starts becoming unpleasant. The good news is that Acetobacter is inhibited above ~35C (95F), so if you keep your mash in the lacto-range you don't need to worry about an oxygen barrier.

I've been experimenting with a number of sour-mashing methods over the years. I've done away with oxygen barriers in my mashes - they're only needed if you cannot keep the temperature up - and, IMO, you end up with a nicer sour profile if the mash has access to oxygen. I've tried letting it cool near the end of the mash to allow some Aceotobacter activity - if done right that can add a nice depth to the beer, but its easy to over-do it (8-12 hours at/below 35C at the end of the sour mash seems to work). More recently I've done a few with pure and mixed cultures, instead of inoculating with uncrushed grain. To date they've ranged from unsatisfactory to horrendous; I've got a post on my blog about one of the worst ones, but a lot of my pure culture attempts have led to "thin" beers that lack the depth of flavour you get from a "true" sour mash.

Bryan
Click to expand...

http://www.homebrewtalk.com/f127/sour-mash-berliner-question-483714/

FATC1TY · Jul 24, 2014

Good info, but like most things with sour beers, I think it's up to the bugs, luck, time and whatever else you want to toss with it.

I've had plenty fine luck souring wort, at what some people would call "cool". I'm sure my luck will run out one day, and thats fine too.

FWIW, I have no interest in not boiling my berliners. So I'm not worried about getting sick or getting others sick, or getting shit bacteria in my tap lines.

jae · Jul 24, 2014

I think Clostridium sp are responsible for the vomity aromas in a sour mash which has turned.

JdoubleA · Jul 24, 2014

I took a Berliner weisse that I made via sour mash (handful of grain method) to my homebrew club last night and it went over well. Man, I was scared of what I had made after the 3 day mash, super bile-y and vinegar-y, even after the boil. And I was even more scared when I went to bottle it and it tasted super bile-y and vinegar-y. But somehow, once it carbed up and chilled, it's just super sour tangy. No idea what happened. I thought I had a acetobacter bomb, but I guess not.

It is kinda horrible once it warms though.

jivex5k · Jul 24, 2014

The thread continued, he says he adds boiling water to the sour mash to bring it back up when the heat starts to drop until he eventually built a heat chamber.

I don't really want to be adding boiling water to keep my temp up, I think I'll just line a cardboard box with aluminum foil and see if that helps. My heat lamp keeps it around 90F right now.

Info on Sour Mash, Oxygen, and E Coli.

jivex5k Initiate (0) Apr 13, 2011 Florida

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Info on Sour Mash, Oxygen, and E Coli.

jivex5k Initiate (0) Apr 13, 2011 Florida

FATC1TY Pooh-Bah (2,564) Feb 12, 2012 Georgia Pooh-Bah

jae Initiate (0) Feb 21, 2010 Washington

JdoubleA Pundit (903) Apr 27, 2011 North Carolina

jivex5k Initiate (0) Apr 13, 2011 Florida

FATC1TY Pooh-Bah (2,564) Feb 12, 2012 Georgia
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