Recipe: Dry-hopped kettle-soured ale

Hi Homebrewers!,

Sour beers are quickly earning their place in the craft beer world as popular and interesting styles of beer. Sour beers can include anything from very ancient styles of beer, such as lambics and Flanders red ales through to more modern kettle-soured beers. Sour beers often use a wide variety of yeasts and bacteria such as Lactobacillus, Brettanomyces, Pediococcus, Wickerhamoyces to name just a few. These yeasts and bacteria produce a wide range of sourness ranging from a mild tartness from yeasts such as Brettanomyces to extreme sourness from Lactobacillus spp. Many of these yeasts and bacteria can also produce flavour that range from tropical fruits to barnyard funk.

There many way to produce these sour beers, ranging from pitching all of the yeasts and bacteria at once to souring in the mash tun to souring the wort in the kettle. Today’s recipe is going to use the latter method (for a super in-depth guide head over to the awesome wiki at Milk The Funk here). Kettle-souring allows for brewers to sour their beer without risking the contamination of brewing equipment. The process involves mashing and collecting the wort as normal, boiling for a short time to sterilise the wort and then cooling to blood warmth. The wort, still in the kettle is then inoculated with your choice of souring bacteria (quite often Lactobacillus) and held at a warm temperature (or not, see here) until the wort has reached a desired level of sourness. The now-soured wort is then boiled again to kill the Lactobacillus and allow for hops to be added (if desired). The wort is then cooled and treated as any other beer.

Today’s recipe is a kettle-soured beer with a Berliner weisse recipe at its base. The recipe has a small charge of bittering hops, however when I first brewed this recipe I did not include it and the resulting beer was still great. Frozen mango and two charges of dry-hops are added after the main fermentation. The hops used in this recipe are Galaxy and Citra, both of which have great tropical fruit flavours including passionfruit and citrus. The recipe also includes a bit of honey after the primary fermentation which gives a subtle honey flavour that compliments the mango and fruity hops. Perhaps one of the most interesting additions to this recipe are the butterfly pea flowers, which turn the beer a vibrant purple colour. You can find them for sale online, but the beer won’t suffer without them.

Keep in mind that this recipe takes around 24-36 hours from mash to fermentor, so don’t brew it on a Sunday and wind up having to finish it Monday morning like I did! Enjoy!

Beer Profile

Batch volume: 20 L
Pre-boil volume: 26 L
Pre-boil gravity: 1.038
OG: 1.046
FG: 1.012
ABV: 4.4%
Bitterness: About 5 IBUs
Colour: 3.3 SRM
Efficiency: 75%

Ingredients

Grains		% of Fermentables
2 kg	German Pilsner Malt (2°L)	47.6%
2 kg	German Wheat Malt (1.6°L)	47.6%
200 g	German Munich Light (6°L)	4.8%
Other Fermentables
1 kg	Frozen mango pieces	90.9%
100 g	Honey	9.1%
Kettle Hops		IBUs
4.5 g	Hallertau [4.7 AA] – 20 Minutes	5
Dry Hops
50 g	Citra [14.3 AA] – 5 Days
50 g	Galaxy [14.3 AA] – 5 Days
Yeast
1 Packet	Fermentis Safale US-05
Bacteria
100 ml	Unpasturised sauerkraut juice (in starter)
OR
1 pack	Wyeast 5335 Lactobacillus buchneri
Other Ingredients
1/2 tablet	Irish Moss – 10 mins
30 g	Dried butterfly pea flowers – Flameout
20 g	Pectinase – Fermentor
Target Water Profile
Ion		Target (ppm or mg/L)
Calcium		60
Magnesium		5
Sodium		10
Chloride		95
Sulphate		55
Bicarbonates		0

Method

Starter

A few days to a week ahead of your brew day, create a 500 ml starter for your lactobacilus with light DME. Once made, add either 1 smack pack of Wyeast 5335 L. buchneri or 30 ml of brine from an unpasteurised sauerkraut (learn how to make your own here). Using either a heat pad, heat belt or fermentation chamber hold the starter at around 37ºC if you can. There shouldn’t be more than a few SG points change in your starter over the next few days. If there is then it is likely that you have a wild yeast contamination and should try again. If this happens when using kraut juice, try using a commercial strain instead (read more about using your own kraut strains on the MTF site here). Monitor the pH, the starter I made from my sauerkraut brine reached a pH of 3.2 in about 48 hours. Once the pH stabilises, place the starter in the refrigerator.

Brew Day

Remove your lacto starter from the fridge. Mash the grains at 65ºC for one hour. Fly or batch sparge at 78ºC for 10 minutes or until you have reached the pre-boil gravity.Bring the collected wort to a boil and boil for 20 minutes. Do not add the kettle hops at this point or they will inhibit the growth of the Lactobacillus. Chill the wort to 37-40ºC and leave the wort in the kettle. 

With the wort still in the kettle, you want to lower the pH to between 4.0 and 4.7. This will help with head retention in your final beer. There is no really easy way to calculate this due to the different buffering capacities of the wort and differences in malt between maltsters. It is simply a matter of adding a few millilitres at a time and measuring the resulting pH. After you have lowered your wort pH add in your lactobacillus starter. Do not add oxygen at this stage. If you can, purge the headspace of your kettle with CO2, which has been said to help prevent the formation of off flavours (although is the subject of debate). You then want to hold the temperature between 37ºC and 40ºC. I do this using a 25 litre electric urn. If you don’t have an urn, you can try using blankets, heat belts, heat pads, hot water baths and even sous vide immersion elements. Just make sure not to mix water and electricity in a way not intended and be careful with using blankets with heat pads and belts. If you don’t have anything to keep the temperature hot, fear not! You can just wrap you kettle in as many old blankets as possible and put it somewhere free from drafts and relatively warm. The lacto will still do its thing as the temperature falls, it may just take a little longer. It took my wort just 12 hours to drop from a pH of 4.7 to 3.7 and I found myself having to do the next part of the brew before work.

After your wort reaches your desired pH bring the wort to a boil. The degree of sourness you choose is up to your own personal tastes, I went with a pH of 3.7. Keep in mind that the pH will likely drop by another few points due to the Saccharomyces fermentation. I felt that the final pH of 3.5 was a good balance between sourness and malt sweetness. Add the kettle hops after the hot break. Add the whirfloc and butterfly pea flowers with 10 and three minutes to go respectively. After the boil cool quickly using a chilling device or no chill package using a cube. Aerate and pitch rehydrated yeast. Ferment at 19ºC adding the mango, pectinase and dry hops after the gravity reaches around 1.018. After the FG stabilises, clarify your beer if you so choose (see here on how to do it) and rack into a keg or into bottles.

Carbonation and Storage

Carbonate to around 2.8 volumes and if bottling store for at least 30 days prior to drinking.