For a long time in brewing, the way to brew sour beers such as Berliner Weisse, Gose, Flanders Red and other beer styles was to brew with mixed cultures, which took its time to create the right level of sourness or flavour. Enter the modern Kettle Sour which aimed to do away with that, by having selected lactobacillus strains that could produce lactic acid in an anaerobic environment at the right temperature in a short amount of time.
Normally, the temperature for kettle souring strains such Lactobacillus Plantarum is between 30-40C or even higher. Which normally would be outside the desirable temperature range of Saccharomyces strains.
Thanks to the efforts of people like Lars Marius Garshol and the farmhouse brewers of Norway in keeping cultures alive, Kveik and other farmhouse yeasts like the Lithuanian Simonaitis can readily survive conditions between 30-40C and still produce good beer.
Putting this together is not my idea entirely, but it was something i stumbled upon after going looking for anything i could find about whether people had done this before. There was some information on Milk the Funk and the HomeBrewTalk forums about this which gave me more of the detail.
To break the method down simply: Pitch hot with kveik with L.plantarum with no hops, and then add hops when the target sourness is reached.
According to the spec sheets published by Lallemand about their Wild Pitch L.plantarum strain, souring is inhibited by as little as 4-5ppm of Beta Acid and Alpha Acid. That’s as little as 2-3g of hops in a 20L batch to reach 5ppm based on the hops being 5% beta acid, pretty standard for most hops.
To put this into practice, you can basically make unhopped wort, pH adjust after boil with acid to less than pH 4.5, chill to less than 40C, add L.plantarum (10g per hL or 2g for a standard 20L batch) and Kveik/Farmhouse yeast e.g. Voss, Simonaitis, Lutra, Hornindal, etc. The pH adjustment is to minimise the effect of the protease enzymes from the Lactobacillus on head retention like you would with a kettle sour. Monitor pH over the fermentation at least every 4 hours, as the souring process will happen very quickly. Normally between 12-16 hours I reach pH 3.7 which is where I like some of my sours to finish up, but go for longer if you want something very sour such as ph 3.2. Once that target is hit, dry hop or add hop tea with at least 5g or more of hops. pH may go down or up slightly after dry hopping as the pH stabilises. As it’s unhopped and may taste a little odd after fermentation completes you can add bitterness by boiling hops in water/wort, or add iso-hop extract to add some bitterness.
Another tip to improve head retention is a protein/foam rich grain in the grist such as Chit, Wheat Malt, Unmalted Wheat, Carapils or Oats.
Note that Lactobacillus Brevis or other lacto strains can be hop tolerant so I wouldn’t recommend this method with those strains. Stick to kettle souring with a boil after souring for those.
Below is a recipe for making 20L of Gose with this method. This is a sour with coriander seed and salt added. Leave the coriander and salt out if you want something more like a Berliner Weisse or a cleaner canvas for adding fruit to make a fruited sour.
“The Quick and the Dead”
OG 1.044 / ABV 4.5% / 0 IBU / 20 Litres
- 62.5% Pilsner or Pale malt (2.5kg)
- 20% Wheat Malt or Unmalted/Flaked/Torrified Wheat (0.8kg)
- 15% Vienna Malt (0.5kg)
- 5% Chit Malt (substitute Carapils if you can’t find that) (0.2kg)
5grams Calcium Chloride added to mash
Single Infusion 67C for 60 mins
10g Salt added to boil
10g Crushed Coriander seed added to boil
60 min boil unless using Pilsner base malt – use 75 min boil.
There is no need to add whirlfloc unless you really want it – this style can be hazy
Add Phosphoric or Lactic acid to kettle post-boil to adjust pH to under 4.5
After boil. chill to under 35C
Pitch 2g Lallemand Wild Pitch plus Kveik such as Lalbrew Voss
Use a heat belt to keep temp above 30-32C
Once target sourness hit, dry hop with 30g Citra, Mosaic, Cascade, Amarillo or other citrusy-style US hop
Make up a hop tea by steeping 10g of hop pellets in boiling water for 10 mins, strain the result and add to the fermenter just before fermentation completes to add a little bitterness to balance the sweetness. Do not overdo the bitterness – bitter and sour don’t work that well together!
I’ve shared the recipe on Beersmith Recipes: https://beersmithrecipes.com/viewrecipe/3292087