This past summer, I wrote a post about sour beer, the different critters that do the dirty work, and different ways of making sour beer at home. Weeks later, Tim and I did our very first sour mash for a Berliner Weisse, so I thought I’d post an update on how it went!

We made our sour mash with 10% of the total grist. Since our recipe called for 3 lbs of German Pilsner malt and 2 lbs of malted wheat, 10% came to 4.8 oz German Pilsner malt and 3.2 oz malted wheat, mashed with 0.2 gallons of water. Because this was such a teeny tiny amount, we just mashed on the stove.

We rested at 97° F for 20 minutes. Then we heated it to 152° F for 45 minutes.

We mashed out at 168° F for 10 minutes, then dumped it in a small cooler, and chilled it to 120° F with ice cubes (made from filtered water).

Here’s where it becomes a sour mash. We sprinkled in a handful of the Pilsner malt (which weighed 0.6 oz). If you remember from my post about this, grain husks naturally contain Lactobacillus delbruckii. 120° F is the ideal temperature for these bugs, so adding a handful of cracked grain once the mash has been cooled to this temperature allows the critters to do their thing.

Next, we let it “cook” for two days, to give the Lactobacillus ample time to produce lactic acid. We kept it outside in the sun during the day, and in a warm spot indoors at night.

After the two days were up, we opened up our mini mash tun to find the nice, clean, sour smell of lactic acid. Excellent. Lactic acid should smell sour, but not unpleasantly so. If your sour mash really reeks, you might have gotten some other bugs in there. If it tastes good, think of it as a happy accident and embrace it. If it tastes nasty, dump it.

We checked the pH of our sour mash, which was 3.4. Nice and acidic, as you would expect!

Now, to carry on with the rest of this brew, we mashed the remainder of the grist as normal, and added enough of the sour mash to hit our target mash pH of 5.2. (We did this at the beginning of a 97° F acid rest). We continued on with the remainder of our mash schedule (saccharification at 152° F, followed by a decoction). Right before mash out, we added in the remaining sour mash, then sparged, boiled, pitched yeast, and fermented as usual.

So, how it did it come out? Well, the sourness was definitely there, though it was a little too subtle for our tastes. Next time, we’ll use a larger percentage of the grist for our sour mash, perhaps up to 20%.

But unfortunately, we accidentally left the glass carboy containing our Berliner Weisse in our basement near a window. Because it was such a pale beer, it got light struck pretty bad (read: skuuuuunky), rendering it undrinkable. Ugh!

We did get learning experience out of this, though I really would have liked to get 5 gallons of beer out of this as well. At least now we know for next time to use a higher percentage of the grist for the sour mash. All in all, sour mashing was a fun process, I’m looking forward to trying it again!