So... What is it?
A kettle sour is made by inoculated the wort after the mash step with a bacteria like Lactobacillus. It's then left to sour for a few hours to days until the pH reaches the desired level which is halted by immediately boiling the wort and carrying on with the brew-day and pitching yeast as you would with a normal beer!
The Berliner Weisse is a sour wheat beer from (you guessed it) Berlin, Germany! characterized by its slightly sour character and light abv (normally around 3-3.9%) it's a fantastic drop for summer in the beer garden, typically having a very light body, tartness on the tongue, and fresh fruity character. This also makes it a fantastic beer for fruit infusions!
What is ours like?
Ours is a "ch-ch-ch-cherry bomb!" and with this being our first kettle sour we stoked with how it turned out! The mouthfeel is a little tart, partly from the souring effect and partly from the cherries, bitterness & hop character very subdued to allow the star's of the show to shine! This Berliner clocked in at 4.7% which is slightly above what the style should be because we didn't account for the cherries sugar! But the cherries come through in spades, with the cherry tartness & subtle residual sweetness pairing beautifully with the sour acidity produced by lactobacillus, producing a gentle sour effect that feels more complex and complete than its philly sour cousin! Making this a super yum beer for sour lovers and the un-initiated alike!
Batch size & ABV
- 19L / 5 gal finished beer
- 20L (6 gal) wort
- Starting gravity – 1.04 (after cherry addition adjusted to 1.046)
- Final gravity 1.01
- ABV – 4.7%
- Final pH - 3.64
- IBU - 11
- we used this calculator to check our ABV after the cherry puree addition
- brewfather link
Ingredients
Water
With sparging
- 15.5L (4 gal) strike water, Mash at 65°C (149°F) for 60 mins, strike temp approx. 69°C (156°F) use our calculator for this
- 15.5L (4 gal) sparge water at 78°C (172°F)
Without sparging
- 30L (7.9 gal) strike water, Mash at 65°C (149°F) for 60 mins, strike temp approx. 66°C (151°F) use our calculator for this
Malts
- Pale ale malt – 1.75 kg (3.86 lb)
- Wheat malt – 1.55kg (3.4 lb)
- Rice Hulls – 150g (5.3 oz)
Fruit Addition
- 3.95 kg (8.7 lb) Puréed Cherries towards end of fermentation (around 1.012 / 7 days)
Hops & whirlfloc tablets
Northern Brewer
- 6g (0.21 oz) - 60 minutes left in the boil
Hallertau Huell Melon
- 15g (0.53 oz) - 15 minutes left in the boil
Whirlfloc Tablets
- 1 tablet – 15 minutes left in the toil OR granulated whirlfloc 0.7g (0.025 oz)
Yeast & Lactobacillus fermentation temperature
- For the kettle souring we pitched 5 bottles of Yakult and allowed it to sour for 28 hours to reach a pH of 3.61
- US-05 – ferment at 20°C (68°F) to 25°C (77°F) 22g (2 packets)
Water Profile
- Ca2+46
- Mg2+ 5
- Na+ 15
- Cl- 55
- SO42- 55
- HCO3- 57
Step by step process
Step 1 – Milling
- Mill grains to medium crush (set mill rollers to a gap of approx. 1.00mm / 0.039 inches)
- Just keep in mind roller gap settings are not universal so as you brew more batches you will find the ideal crush size for your setup
- Alternatively if you don’t have a grain mill you can order your grains crushed from most homebrew stores, both online and in person
Step 2 – Mashing
- Mash for 60 minutes at 65°C (149°F)
- Set your strike water to a few degrees above the target mash temperature, you can use our calculator to determine what your strike temperature should be
- ensure you mix in the grains thoroughly with a mash paddle to prevent dough balls from forming (big spoons, spatulas or whisks will also work)
- its easier to mash the grains and prevent dough balls if you add a little grain at a time, mix, add more grain and repeat until all the grains are mixed
- if you don’t have a mash tun with heating then ensure after you have finished mixing the grains in to insulate your mash tun (thick neoprene or heavy blankets both work well)
Step 3 (optional) – Sparging
- if your setup has the capability to sparge then do so with 15.5L (4 gal) sparge water at 78°C (172°F)
- if you are not sparging and using a BIAB (brew in a bag) method then remove grains from mash tun and twist and squeeze the bag to get as much liquid out of the grains as possible
- as you start sparging (or straining your BIAB bag) begin raising the temperature of your wort to a boil
Step 4 Souring!
- At this point allow your wort to cool down to 30-33°C (86-91.4°F) and then pitch 5 bottles (325mL / 11 oz) of Yakult into the wort, this will pitch around 325 billion cells!
- If you can keep the temp around 30-33°C (86-91.4°F) whilst it sours, and at this point you are at the mercy of the lacto!
- Check the pH using a pH meter every 6-12 hours until it reaches your desired level and then immediately move on to boiling!
- We allowed ours to reach 3.61, but aim for anywhere between 3.3 - 3.6
Step 5 – Boiling
- once your wort begins to boil start a timer for a 60-minute boil and add your bittering hops, 6g (0.21 oz) of Northern Brewer
- at 15 minutes left in the boil add 1 whirlfloc tablet (OR granulated whirlfloc 0.7g (0.025 oz)) and 15g (0.53 oz) of Hallertau Huell Melon
Step 6 – Whirlpooling / cooling
- once wort has been boiling for 60 minutes in total turn off your heat source and begin chilling wort down to yeast pitching temperature
- once you’ve reached yeast pitching temperature take an original gravity reading of your wort
Step 7 – Yeast Pitching
- It is best to make a yeast starter before beginning your brew day (ideally 1 day before) to ensure your yeast are as active and healthy as possible before pitching, but not completely necessary – you could also just rehydrate yeast 30 minutes before pitching.
- Wort Aeration (Optional) if you have a paint mixer give your wort a quick blitz before pitching yeast to help add more dissolved oxygen into the wort to help the yeast have a healthier kick start into fermentation
- Pitch yeast in wort a degree or two higher than the target fermentation temperature to help yeast take off more aggressively
- To make a yeast starter you can use either:
- DME (dry malt extract) at a ratio of approx. 100g per 1L water (3.5 oz per 33 fluid ounces) for gravity of approx. 1.040
- some unfermented wort kept cold and sanitary from a previous brew day
- 70g of table sugar per 1L water (2.5 oz per 33 fluid ounces) – however, it is best to use malt sugar (wort / DME) whenever possible to reduce the chance of shocking the yeast with a different food source from starter to wort pitching
- To rehydrate yeast
- Add yeast to approx. 10 times as much room temperature water as the weight of the yeast e.g. 10g yeast in 100 ml water (0.35 oz yeast in 3.5 fluid ounces water)
Step 8 – Fermentation & Fruit additions!
- Allow yeast to ferment over the next two weeks (aprox)
- If you have a temperature-controlled system keep the fermenter temperature to the recommended fermentation temperature for each yeast strain (stated in the yeast ingredients section above)
- Monitor the fermentation activity over the first 7-10 days by the bubbling of the blow-off tube/airlock of your fermenter, as the bubbling slows down (roughly around day 10-12) take a gravity reading. When the gravity reaches around 1.015 raise the temperature of your fermenter by 1-2 degrees for 2 days for a diacetyl rest (if you don’t have temperature control don’t worry about this step, it's not the end of the world!)
- Time to add fruit! purée 3.95 kg (8.7 lb) of Cherries and throw them all into the fermenter
- we used this calculator to check our ABV after the cherry puree addition
- It's important to note that fermentation times will vary based on your circumstances like temperature, amount of yeast pitched, the healthiness of yeast, the gravity of the wort, pH, etc. so don’t stress be patient and know that these times are just a rough guide
- On day 2 of the diacetyl rest (once gravity reaches roughly 1.008-1.01) & gravity is the same 3 days in a row move onto cold crashing! (If you can’t / don’t want to cold crash go straight to kegging/bottling your beer!)
Step 9 (optional) – Cold crashing
- begin cold crashing your fermenter (bring the temperature of your fermenter down to as close to 0°C (32°F) as possible, for 2 days to a week depending on how patient you are
- If you don’t have a temp-controlled fermenter, you can cold crash by putting your fermenter in a fridge or temp-controlled chest freezer
- After you have finished cold crashing it's time to keg/bottle your beer! If you are bottling your beer from the fermenter uncarbonated remember to add about 5-7grams (0.17 - 0.24 oz) of priming sugar to your bottles to carbonate your beer.
