Quick and simple sour beers were always something I was interested in making. I often assumed however that they were very difficult to dial in and get right, and that you could very easily make something awful (heard many stories of beers smelling like baby poop 🤢). This post about kettle sours convinced me to finally take the plunge. That, and I needed to make a beer for my wedding since my wild yeast beer didn’t turn out. I decided to go with kettle sour over a sour mash since I was planning to use a commercial lacto strain and not get my lacto from the grain.

Here’s the recipe I used, along with steps of my process.

Recipe

This is the base recipe, of which so far I’ve made the same batch twice now but with two separate fruit additions (Cherry and Raspberry). Beersmith Link

Batch Details

Batch Size: 2.91 gal Style: Berliner Weisse (23A) Boil Size: 4.31 gal Style Guide: BJCP 2015 Color: 2.9 SRM Equipment: 2.5 Gal BIAB Bitterness: 8.1 IBUs Boil Time: 60 min Est OG: 1.034 (8.6° P) Mash Profile: BIAB, Medium Body Est FG: 1.007 SG (1.9° P) Fermentation: Ale, Two Stage. Temp 18C ABV: 3.5% Target PH: 5.3

Ingredients

Amount Name Type # 0.83 g Gypsum (Calcium Sulfate) (Mash 60 min) Misc 1 1.32 g Calcium Chloride (Mash 60 min) Misc 2 4.13 tsp Lactic Acid (Mash 60 min) Misc 3 2 lbs Pilsner (2 Row) Ger (2.0 SRM) Grain 4 2 lbs White Wheat Malt (2.4 SRM) Grain 5 0.20 oz Citra [12.0%] – Boil 15 min Hops 6 1 pkgs Omega Yeast Labs OYL-605 (Lactobacillus Blend) Yeast 7 1 pkgs Safale American (DCL/Fermentis #US-05) Yeast 8 1200g Frozen Fruits (Post Fermentation) Fruit 9

Mash Schedule

Target Mash Temp – 66.7C (152F). Mash out @ 75C for 10 minutes.

Process

Add 18.15L of water to Kettle. Add Gypsum, Calcium Chloride, and Lactic to kettle. Heat water to strike temp (69.1C). Heat sources: stove top & Sous vide. Once strike temp is reached, add milled grains to kettle inside of BIAB mesh bag. Turn off stove top and set SV to Target mash temp. As the mash rest occurs, fill a large plastic container with water. Set a second SV in the container, temperature set to 32C/90F Once mash is complete, pull bag and drain all liquid from the bag. Remove SV and turn stove top heat to max. Boil the wort for a quick 5 minutes. Turn off the heat, chill wort to 32C/90F with immersion chiller Submerge the kettle (with lid on) into plastic container water bath (step 3) Check the pH of the wort. Add lactic acid to get pH down to around 4.5. Ensure that wort does not get aerated. Pitch a pure lacto culture (OYL-605 is what I used). Seal the opening of the kettle with plastic wrap, and place the lid on top. After 12-24 hours, check pH. If pH is 3.6 or lower, you’re good to boil. If its higher, check again in a few hours. Remove kettle from water bath, and boil the wort for 60 minutes. Add any hops based on the recipe Chill wort to target fermentation temp (18-22C). Transfer to a carboy (or preferred fermentation vessel), aerate and pitch desired yeast (I used dry yeast – US05). Once Final gravity is reached, add frozen fruits (various methods to do this, see below) Let the beer sit on the fruit for 1-2 weeks. Bottle or Keg as normal. A cold crash for a portion of step 15 can help the fruit settle out.

Results

So far I’ve made two batches with this recipe + process. A Raspberry sour and a Cherry sour.

Raspberry Sour

The souring of this batch went fairly well. After mashing and a quick boil (Suggested by MTF to kill some competing microbes) my pH was 5.43. I added 4.8mL of Lactic Acid which dropped it to 4.6. Added 2mL more which got it down to 4.39. After pitching OYL-605 and waiting 24 hours, the pH was 3.06. This was a bit lower than I was intending as this was meant to be a wedding beer, and a lot of attendants had never had a sour beer. So I was hoping that it would be at least approachable. At this point I was hoping the fruits would balance the sourness a bit.

Measured OG: 1.030 Measured FG: 1.001

Once FG was hit on this batch, it was time to add the fruit. I went with Frozen raspberries (Whole Foods 365 Raspberries). I used 1200g, which worked out to four packs of them. The initial plan was to blend it all in a sanitized blender, by my blender wasn’t working too well so I decided to heat them up a bit to break them down and also pasteurize. Once it was basically a thick puree, I added it to a new sanitized carboy, and racked the finished beer on top of the puree.

I let it sit for a week (would have done two but was tight for time), transferred to a keg and carbed it.

Overall this came out great. It was on the moderate sour side unfortunately (so a bit off of a Berliner Weisse target), but the raspberry sweetness helped to balance things out. Lots of wedding guests enjoyed it, not having had a sour beer before.

Cherry Sour

Next up when rebrewing this I wanted to try another base fruit. Went with Cherry this time. Souring was almost identical to the previous sour. Same lacto strain was used. Initial pH was 5.35. 5mL of Lactic acid added got that down to 4.4. 24 hours post pitching of the lacto culture resulted in another pH of 2.96. I had planned to check this before the 24 hour mark, but had forgotten. So again this would be on the moderate sour side when my goal was a lighter sour.

My measured OG was 1.034 and measured FG was 1.011.

I decided not to do any sort of blending/breakdown of the fruit and instead just dump it straight into my carboy. I did get some aeration when adding the cherries which is a not something you want to do post fermentation, but I couldn’t avoid it using a carboy with a small opening. It would be interesting to see the differences in fruit flavours+intensities between this and the raspberry sour batch (which was blended).

Picture taken after pitching fruit Picture taken after two weeks on fruit

This batch came out quite similar to the Raspberry batch, as expected for the most part. It didn’t seem any more sour than the previous batch even though its pH was lower. What was different was the fruit intensity+quality. The raspberry batch had alot more character than this batch. Which could be due to the blending vs non-blending. Or it could be due to the type of fruits being different.

Thoughts

Overall I think this method works pretty well, and is simple to follow. The one complicated/tricky point might be the SV bath to keep the temp at 90 during souring. This could be seen as an optional step if you are using a pure lacto strain (commercial purchase) – even the OYL-605 information page states that the strain can sour at lower temps (65F- 100F). Holding a high temp would probably be more required if you culture your own lacto off of grains/other sources.

My plans are to do a Mango(!) version of this next. I like the strain I used (not quite ready to culture my own yet) so will probably use that, maybe without the big water bath.

Best of luck if you try this! Let me know your results or if you have other kettle sour methods to share!