Ok folks.
Yesterday morning I mashed in 10 gallons of a Berliner Weiss, cooled to 120° and then threw a cup of 2-row on top.
I then purged with CO2, covered with Saran wrap and purged again and covered in my Igloo cooler.
I have been checking temps and they are not too bad but dropping. I checked this morning and it was at 105°.
I was going to heat it back up by placing boiling water into the mash and here is where my question is.
When adding boiling water, do I stir up the entire mash?
(Won't that introduce oxygen?)
I want to sour for at least 48-72 hours (dictated by taste).
So far it smells good, well... It doesn't smell bad. Just like plain yogurt.
Input please... Thanks.
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
