How To Brew a Delicious Kettle Sour

Kettle Sour

For years at the beginning of my brewing career, I swore I would never brew a sour beer. I couldn’t imagine purposely adding lactobacillus to any part of my brewing process. Even after I discovered the kettle souring process, I was hesitant. But, it is hard to deny its popularity, and when done right, it is a wonderful addition to your spring and summer tap list. This kettle sour recipe is based on a Gose, whose style guidelines are below.

  • Original Gravity: 1.036 – 1.056
  • Final Gravity: 1.006 – 1.010
  • Alcohol by Volume: 4.2% – 4.8%
  • Bitterness: 5 – 12 IBU
  • Color (SRM): 3 – 4

Kettle Sour Ingredients

Malt

The Kettle Sour has a simple grain bill, consisting of Wheat Malt and Pilsner Malt. You can split it right down the middle at 50/50, or add slightly more wheat at a 60/40 ratio. Since we are adding a large percentage of wheat, I recommend adding about 1/2 a pound of rice hulls per 5 gallons to stabilize your mash bed.

Hops

The Gose has a very low bitterness, so we only add 5 IBUs to this Kettle Sour. Bitterness does not mix well with the sour character, and the low pH changes the hop utilization, so I recommend starting low in your first batch and adjusting in later iterations. For this Kettle Sour, I skip the usual 60-minute bittering addition and add Mandarina Bavaria at 30 minutes and flameout to enhance the citrus flavor and aroma.

Yeast

The yeast strain depends highly upon the beer style you are brewing. Just make sure it is a hardy strain to withstand the low pH. For this batch, I used White Lab’s California Ale yeast.

Water

Last but not least, the water. I use a reverse osmosis filtration system and build my water profile from scratch. My water profile looked like this:

  • Calcium: 50 ppm
  • Sulfates: 55 ppm
  • Chloride: 60 ppm

Recipe

The following is a 5-gallon version of our Kettle Sour. The numbers for this beer are listed below.

  • Original Gravity: 1.044
  • Final Gravity: 1.008
  • Alcohol by Volume: 4.73%
  • Bitterness: 5.0 IBU
  • Color (SRM): 3.0

Grain Bill

  • Wheat Malt – 4 lbs (50%)
  • Pale Malt – 4 lbs (50%)

Hops

  • 0.26 oz Mandarina Bavaria (6.7% AA) @ 30 minutes – 5 IBUs
  • 0.2 oz Mandarina Bavaria (6.7% AA) @ Flameout
  • 0.15 oz Himalayan Pink Salt @ 5 minutes
  • 0.3 oz Cracked Coriander @ 5 minutes

Yeast

  • California Ale Yeast – WLP001

Bacteria

  • Lactobacillus Plantarum – WLP693

Mash

Add your salts if needed, and fill your mash tun to the required volume and temperature for your mash to drop to 152 degrees Fahrenheit. For me, it was 2.5 gallons at 163 degrees Fahrenheit. After 60 minutes, raise your mash temperature to 168 degrees for mash out. After mashing out, sparge until you reach a pre-boil gravity of around 1.037. For me, it was 5.50 gallons.

Pre-Acidification

Once the sparge is complete, we must pre-acidify our wort to a pH of 4.5. We can do this with phosphoric or lactic acid. This will help prevent other bacteria and yeast strains from inoculating our wort, leading to undesirable flavors such as butyric and isovaleric acid. It will also limit protein-degrading enzymes, which will hurt our head retention if we allow them to work while the lactobacillus works its magic.

Boil #1

Once your wort has a pH of 4.5, bring it to a boil and hold it there for 15 minutes to pasteurize it. This will kill any wild bacteria and yeast the wort may have picked up. Do not add any hops during this boil. Hops will severely inhibit the lactobacillus we are about to add.

Add Your Lactobacillus

Once your wort has boiled for 15 minutes, cool it to 90 degrees Fahrenheit and pitch your lactobacillus. If your equipment allows it, put a blanket of CO2 on top of the wort and seal your kettle. Take pH readings every couple of hours. Aim for a pH of 3.5, which should take around 48 hours if you can hold your kettle at 90 degrees Fahrenheit. You can maintain 90 degrees with a heat wrap, an electric heater, or periodically turning on a gas burner.

Boil #2

Once your wort pH reaches 3.5, continue the rest of the brew day as normal, starting with the boil. Boil the wort for 90 minutes and add the hops in as needed. At 10 minutes, I added a yeast nutrient, which is particularly important with this style due to the lower pH. Once the boil is complete, whirlpool the wort for 10 minutes and then let it wind down for 10 minutes.

Fermentation

Knock the wort out in your heat exchanger so that the pitching temperature is 64 degrees and then measure the gravity and pitch the yeast. Make sure to adequately oxygenate your wort. Initial gravity should be around 1.044. I let this free rise to 67 degrees as fermentation starts. Hold the temperature at 67 degrees for 5-7 days until the primary fermentation starts to slow down, and then let the temperature free-rise up to 72 degrees to finish. Once the fermentation is complete, we will add our flavoring.

Adding Flavoring

Since the flavoring we will add contains new sugars, we need to neutralize our yeast. We can do this by pasteurizing, filtering, or adding potassium sorbate and potassium metabisulfite. I do not filter or pasteurize, so I must add the preservatives. I dose them at a rate of 1/2 tsp per gallon of potassium sorbate, and 1/4 tsp per 6 gallons of potassium metabisulfite. These two additions do not kill the yeast, but they prevent them from reproducing. Add these two ingredients after the diacetyl rest and leave them in contact with the beer for at least 24 hours.

Once the potassium sorbate and metabisulfite have been in contact with the beer for 24 hours, cold crash to 33 degrees. Keep the beer cold crashed for at least a day. Immediately before transferring to your brite tank or keg, add your choice of puree to your sanitized vessel. We recommend taste testing different doses of puree via 4-ounce samples of the kettle sour beforehand. It will not take much more than a couple of mL of puree to get the desired flavor. For the puree, we love the company Amoretti. They have countless options and all of them are extremely high quality.

Once you have added your desired amount of puree to your sanitized brite tank, transfer your beer. Adding the puree first allows the beer to evenly mix in with the puree during the transfer without the risk of adding additional oxygen. Once everything has been added, carbonate it to 2.7 vols. After 3 days in the brite tank, keg it, and enjoy!

If you decide to try this recipe, or another Kettle Sour recipe, feel free to send us a comment and let us know how it went! And if you want to see more recipes like this, sign up for our newsletter below to be notified when a new post is released. Cheers!

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