Oakshire Brewing Co.’s Key-Limety Kölsch clone

(5 gallons/19 L, all-grain)
OG = 1.046  FG = 1.008
IBU = 22  SRM = 4  ABV = 5%

Brewed to include the addition of key lime puree, this Kölsch uses a semi-traditional Kölsch grist bill along with a big helping of honey. Fermented with Kölsch yeast and finishing dry, this is a very fun one. Feel free to omit the fruit or substitute another fruit for key lime, as Oakshire has done on occasion.

Ingredients
3 lbs. (1.4 kg) Weyermann Cologne malt
2.5 lbs. (1.1 kg) Weyermann Pilsner malt
1.5 lbs. (0.68 kg) Weyermann Barke® Vienna malt
8 oz. (227 g) Weyermann CaraFoam® malt
4 oz. (113 g) acidulated malt
1.5 lbs. (0.68 kg) honey, any varietal (10 min.)
24 oz. (710 mL) key lime puree 
4.3 AAU Nugget hops (60 min.) (0.33 oz./9 g at 13% alpha acids)
5.6 AAU Sultana^TM hops (10 min.) (0.4 oz./11 g at 14% alpha acids)
0.4 oz. (11 g) Lemondrop^TM hops (0 min.)
Whirlfloc tablet (15 min.)
1⁄4 tsp. yeast nutrients (15 min.)
White Labs WLP029 (German Ale), Wyeast 2565 (Kölsch), or SafAle K-97 yeast
3⁄4 cup corn sugar (if priming)

Step by Step
If using soft or reverse osmosis brewing water, add 1⁄2 tsp. 85% phosphoric acid, 3⁄4 tsp. calcium chloride, and 1⁄4 tsp. calcium sulfate. Mash the grains at 152 °F (67 °C) for 60 minutes before beginning the lauter process. Add 1⁄2 tsp. 88% lactic acid directly to the kettle. Bring wort to a boil and boil for 60 minutes adding the hops, honey, kettle fining agent (Whirlfloc), and yeast nutrients per the ingredients list.

At the end of the boil, turn off the heat and add the final hop addition. Create a whirlpool then let settle for 10 minutes. Chill the wort down to yeast pitch temperature then pitch the yeast. Ferment at 64 °F (18 °C). After peak fermentation has been reached and fermentation slows noticeably, add the lime puree. Raise temperature to 68 °F (20 °C) and hold for 2–3 days. Once terminal gravity has stabilized, drop the temperature to 32–40 °F (0–4 °C) for a one- to two-week lagering period. Keg and force carbonate to 2.5 v/v or bottle and prime with sugar. 

Extract with grains option: Replace the Cologne, Pilsner, and Vienna base malts with 3.5 lbs. (1.6 kg) Pilsen dried malt extract and 0.5 lb. (230 g) Munich dried malt extract. Replace the acidulated malt with 1⁄2 tsp. 88% lactic acid. With 5 gallons (19 L) of water in the brew kettle, add the lactic acid. Steep the crushed CaraFoam® malt in a small muslin bag as the water heats up to 170 °F (77 °C). Remove the grains, allowing liquid to drip back into the kettle. 

Off heat, stir in the dried malt extract. Once fully dissolved turn the heat back on and bring to a boil. Follow all-grain instructions for the remainder of the process, being sure to top up the fermenter to 5.25 gallons (20 L) before starting fermentation.