Friday, September 26, 2014

Sour-Worted Soma

One of my main homebrewing projects/focuses for the next year is developing ways to get a reliable and repeatable tartness or light acidity into beers which I ferment 'clean' (meaning without Brettanomyces or bacteria, only Saccharomyces). My basic goal for doing this is to ferment a 'clean' beer in a normal ale time frame while still achieving a refreshing tartness. I am definitely not interested in using this method to provide all the acidity in a beer that is fully sour. For these beers I will still use mixed fermentations, where the flavor development during a slow acidic fermentation will result in what I think is a much better beer than relying only on quick pre-primary souring. I talked about more about my motivations for pre-primary souring and methods like sour worting in this post.

I've frequently used pre-primary souring methods in my saisons to add a tart edge to an otherwise normal beer. I find this helps the refreshing aspects of the beer and, in this style, that refreshing character is an important part of what makes the beer. Usually I use acidulated malt out of ease, but I've done some sour mashes with good results. This beer is based off a recipe which I initially sour mashed, but this time I wanted to try sour-worting (which I learned of from the Mad Fermentationist). This technique involves souring wort with Lactobacillus and then re-boiling this soured wort and fermenting it without bacteria. In my case I decided to only sour a portion of the wort which I pulled off a previous batch and I would blend back in during the boil of this beer.

The soured portion after adding it back in the boil
A couple weeks before this brew I brewed a similar saison which ended up going into an oak barrel, and I took the opportunity to produce some extra wort to pull off for souring. I decided I would leave the batch at room temperature as I had time to wait and while lacto may thrive at elevated temperatures, it certainly works fine at ambient temps as well. There was a small snag, that I didn't have any Lactobacillus around. So I used the dregs for The Bruery's Hottenroth, a beer almost completely fermented with Lactobacillus. Unfortunately I didn't get a chance to make a starter with that and while it did add a bit of acidity, it took some time to get going. Fortunately I was able to pick up a pack of the Wyeast seasonal Lactobacillus brevis. So after about a week and a half of mild souring I added a the lacto, which dropped the pH down to 3.5 over the next week. At that point I was happy with the acidity of the sour-worted portion and I was ready for the brew day. I've made sure to leave some of the wyeast lacto around so that I'm prepared for future sour worting trials and I don't have to go through quite as much extended pre-souring.

Target OG: 1.052
Volume: 7.5 gallons
IBU: ~25-30, though I didn't end up calculating it for this batch
FG: ~1.002-1.001
ABV: 6.7%

86.4% Doehnel malt #25 (1.5 L light pilsner), more about Doehnel malts here
9.1% Doehnel malt #27 (6-7 L Light Munich)
4.5% Acidulated malt (Weyermann)

85g Czech Saaz pellets, 3.6%aa
29g Hallertauer Mittelfrueh pellets, 4.8% aa
57g Tettnang pellets, 4.3% aa

1/2 tsp Wyeast yeast nutrients
My standard Wyeast 3724 and 3711 blend (more about blending here)
Dregs from The Burery's Hottenroth
Wyeast 5223 Lactobacillus brevis
Yeast Bay Lochristi Brett blend

Salts and other:
8 g CaSO4, 6 g CaCl2 in 6.5 gallons of mash water (+120 ppm Ca2+, +181 ppm SO42-, +79 ppm Cl-)
5 g CaSO4, 2 g CaCL2 in 4 gallons of sparge water (+101 ppm Ca2+, +184 ppm SO42-, +43 ppm Cl-)
Note: Victoria's base water is very low in minerals, so the final mineral concentrations are basically the same as the added concentrations.
1 tab whirlfloc

The Mash
Mash Plan:
146F (63.3 C) for 50 minutes, 5-10 minutes of recirculating with heat to raise the temp to 154 (67.8 C) for 20 minutes. 1/2 of the acidulated malt will be mashed with the rest of the grist and 1/2 will be added to the mash with 10-15 minutes left. I overshot the 154 by a bit and ended up spending the last 20 minutes between 156 and 158 F (68.9-70 C). This shouldn't really be a problem as the bulk of my conversion happened during that first 50 minutes and the second step is to finish everything up quickly (and it would probably happen more quickly at 156-158F/68.9-70 C). So it should not have a huge influence but it was definitely not my goal.

Collecting runnings
Boil Plan:
90 minute boil. After 30 minutes of boil the sour portion (now at pH = 3.5) will poured into the wort. A small portion of the soured portion will be left behind and final wort will be added back to the sour carboy to allow the beer to continue to sour with lacto in the primary. 3 hop additions: 42 g Tettnang and 56 g Saaz with 20 minutes left in the boil, 15 g Tettnang and 15 g Saaz with 5 minutes left in the boil and 14 g Saaz and 28 g Hallertau at flame out for a 15 minute hop stand.

About to finish the boil
After blending in the pH = 3.5 soured portion to my pH = 5.1 wort, the pH dropped to 4.2. It smelled nicely lactic and tasted good at this point. You do have to be careful with too low of a pH inhibiting Saccharomyces (I don't know what a typical threshold value would be), but I didn't notice any problems like that with this batch.

I used a blend of 3724 and 3711 (~80% 3724 and ~20% 3711, ~255 billion cells total) into the two carboys - one clean and the live lacto carboy with wort added back in (more on how I blend yeasts here). I pitched the blend at 68 F (20 C) and steadily to 78 F (25.6 C) over the first 2 days. I held the temperature steady at 78 (25.6 C) for the next 4 days and then at day 6 I raised the temp to 80 (26.7 C) until the beer reached it's terminal gravity, at which point I turned off the aquarium heater I was using to keep it warm and let the temperature fall down to the upper 60's (~20 C), which is my room temperature.
The bottled beer

I bottled the beer on August 12th. I am reasonably happy with it and find that it is improving with a bit more time in the bottle. I'll give it full tasting notes in the next week or two.


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  2. How many gallons of the soured wort did it take to drop the pH down to 4.2?

    Thanks for a lot of inspiration and a great blog!

    1. Thanks Tim! It was about 2-2.25 gallons. And that went into about 7.5 gallons of boiling wort to give the final blended pH of 4.2. But it is all going to depend on how sour your acid component gets.

      Also, looking back on this, I definitely did not go about it the best way. I should have had a larger and active pitch of lacto ready to go when I made the initial sour portion. ad I done that, the sour worting would have gone much quicker (likely a couple of days).

      Good luck with your blending and let me know if you have more questions!