Brewing Mountain Sour #5

While awaiting the Squarrel-aged Mountain Sour (batches #1-4) to mature, I brewed Mountain Sour #5, a Catharina Sour, for drinking now.

A Catharina Sour is a Brazilian standard-strength kettle-soured wheat ale that features fresh (often tropical) fruit. While similiar, Catharina Sour it is more potent than Florida Weisse and more fruit-focused than Berliner Weisse.

With summer 2020 fast approaching, I wanted to have cans of fruity sour beer at the ready. I leaned heavily on Gordon Strong’s Catharina Guajava recipe for the inspiration behind Mountain Sour #5.

Malt / Mash

Pilsner and wheat malt make up the entire Catharina Sour grist, up to a 50-50 split. For Mountain Sour #5, I used 65% Mecca Grade Estate Malt Pelton (Pilsner) and 35% Shaniko (White Wheat) Malt. I just as easily could have used Lamonta (Pale) and Wickiup (Red Wheat) Malt, but I wanted the grist to be a blank canvas and stay out of the way of the fruit and acidity. To optimize attenuation, I used a three-step infusion mash starting at 122°F for 5 minutes, 153°F for 70 minutes and 169°F for 10 minutes.

Hops / Boil

As a kettle-sour, I boiled Mountain Sour #5 twice; once before adding lactic acid bacteria and once after the wort hit my target pH.

The first boil contained no hops and lasted just 10 minutes to solely sterilize the wort. After the boil, I chilled the wort to 113°F. To improve head retention and suppress any potential contaminants, I pre-acidified the wort by adding 7 ml of lactic acid to reduce the pH to 4.5. Next, I pitched 4 oz of GoodBelly Probiotics Mango (Lactobacillus Plantarum) and purged the keg with carbon dioxide. I checked the pH every 12-24 hours until it reached 3.5 pH. Unfortunately, the wort souring took a lot longer than expected due to the ambient fermentation temperature (I did not keep the wort heated) but after six days, I commenced the second boil.

The second boil lasted 60 minutes and included an 8 IBU addition of Columbus pellet hops at 30 minutes as well as yeast nutrient and whirfloc at 15 minutes. Once complete, I chilled to 85°F and pitched Imperial Yeast A43 – Loki. I maintained the 85°F temperature for most of the fermentation duration.

Yeast / Fermentation

A34 – Loki is a Norwegian Voss kveik yeast strain that has a massive fermentation temperature range (65°F to 100°F). Fermentation temperatures >85°F result in a huge fruit ester profile, which is exactly why I fermented at 85°F. After three days of fermentation, Mountain Sour #5 reached a specific gravity of 1.009, at which point I added 49 oz of Vintner’s Harvest Apricot Purée (fruit rate of 1.19 lb/gal). In about two weeks Mountain Sour #5 should be ready for packaging.

Water

Since I haven’t yet tested my city water, I opted to use 3.11 gal of distilled water configured to my saison target profile of 52 ppm calcium, 17 ppm magnesium, 35 ppm sodium, 20 ppm chloride, 107 ppm sulfate, and 165 ppm bicarbonate. I added 0.47 g gypsum, 0.22 g calcium chloride, 2.03 g epsom salt, 0.21 g canning salt, 0.47 g slaked lime, 0.84 g baking soda and 0.47 g chalk to reach my target. I also added 4 ml of lactic acid for a mash pH target of 5.34 (but ended up a little higher at 5.48 pH).

Recipe

The Mountain Sour #5 recipe can be found here: https://share.brewfather.app/1SGhrXaNrvNP0x.

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