Homebrew Recipe: Velvet Unterbahn Kettle-Soured Gose

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This month: a traditional Gose produced with a modern souring regimen. Since long preambles are for single-strain fermentations, let’s dig right in.

A recipe to try

Velvet Unterbahn Gose
Target OG: 1.048, Target IBU: ~7

Grain

  • 4 pounds Weyermann® Pilsner
  • 4 pounds Weyermann® Pale Wheat
  • 8 ounces Weyermann® Acidulated malt

Hops

  • ½ ounce your choice of a classic continental low-alpha noble hop (Hallertauer, Hersbrucker, Tettnang, Saaz, etc.)

Yeast

  • Wyeast 5335 Lactobacillus
  • Your choice of a clean German ale strain (Wyeast 1007 or Safale K-97 would be good here)

Other

  • ½ ounce sea salt
  • ½ ounce whole coriander

Key points for key pints

• Why kettle sour? Kettle souring adds a fairly big step to the brewing process, but brings a couple big benefits: mainly, it can usually sour a beer faster than co-inoculating, and it eliminates any risk of cross-contaminating your fermenting or packaging equipment. Since Lactobacillus and Saccharomyces are added individually, fermentation conditions can be optimized sequentially rather than splitting the difference; and since the wort is boiled post-Lacto fermentation, the bacteria are destroyed before the pre-soured wort reaches your fermenter or bottling gear.

• How to kettle sour. Kettle souring requires a big dose of bacteria, so we’ll propagate a pack of Lactobacillus ahead of time. On brew day, mash and sparge like normal, followed by a cursory boil to sterilize, then cool. Pitch Lacto and ferment right in the boil kettle; keep it warm for a couple days, then boil again, add hops, and so on.

• Our friend Lactobacillus. It’s anaerobic, thermophilic, inhibited by isomerized hop acids, and mainly homofermentive—so it likes hot fermentation temps, hates O2 and hops, and should reduce pH rather than SG.

• Source good coriander and grind it right before use. We want lemony and zingy, not vegetal/celery/ham from old, stale seeds. I’ve had good luck with Penzey’s.

Related post: Homebrew Recipe: La Granja Agave Azacca Saison

To the homebrewery

Note: these steps are general guidelines and assume you’re already familiar with the all-grain brewing process. Refer to the instructions for your brew system and adjust as needed based on experience with your own particular equipment.

Prep: 1–2 days before brew day

1. Prepare a Lactobacillus starter: 1 liter of water, 4 ounces DME. Incubate at a very warm temperature (85–100°F) without stirring or agitation.

Prep: On brew day

1. On brew day, collect strike water and heat to approximately 165°F.

2. Mill the grains, or have it done for you at the shop.

Mash & sparge

1. Add all grains to strike water and mix to achieve a uniform temperature of 151–153°F. Rest the mash at this temperature for 60–90 minutes.

2. While the mash rests, collect and heat sparge water.

3. When the mash rest is complete, heat it to 170°F for mashout.

4. Sparge and collect the wort in the boil kettle.

Kettle souring

1. Use a boil kettle that has a well-fitted lid. Bring the wort to a boil for a couple minutes to sterilize, then allow to cool; you can use an immersion chiller if you like, or just let it cool passively with ambient temps. (Don’t worry about DMS formation at this point—the wort will be boiled again.) Keep the wort in the kettle—no need to transfer, the lactic fermentation will take place right in the boil kettle.

2. Once the wort temp is below 120°F, inoculate with the entire Lacto starter and cover the kettle with the lid. (If you want to go all-out, flush the headspace of the kettle with CO2.)

3. Allow Lactobacillus to ferment 1–3 days. Do not oxygenate or aerate, and maintain a fermentation temp of 80°F or above—all other things equal, the bacteria will work faster at warmer temps, up to about 120°F, in an anaerobic environment.

4. Once the wort has soured to your liking (a simple sensory evaluation of the sour wort will be enough), proceed to the main boil.

Main boil

1. Bring the soured wort back to a boil and hum along to “White Light/White Heat.” Add 0.5 ounces of your selected noble hops when the wort begins to boil, and boil for 60 minutes.

2. During the boil (you should have plenty of time during “Sister Ray”), grind the whole coriander seeds using a spice mill, mortar and pestle, or whatever method you choose.

3. Add the charges of ground coriander and sea salt five minutes before the end of the boil.

4. Cool it!

Fermentation and beyond

1. Transfer the cooled wort to a sanitized fermenter, aerate well, and pitch yeast.

2. Depending on the yeast strain being used, aim for a maximum fermentation temp in the low to mid 60s°F.

3. When gravity is stable and the beer is sufficiently clear (some haze is accepted and expected for this style), proceed with packaging.

4. Our kettle-soured Gose will show best while fresh—but why would you sleep on this tart, refreshing little gem during our brief Minnesota summer in the first place?

Until next time: Drink it like you brewed it.

 
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