Testing reiterated mashing – Cricket Balls (Imperial Stout based on Black & Deep from Drunken Bros)

In spring 2019 Drunken Bros Brewery announced that they were not going to brew Black & Deep, their iconic Imperial Stout brewed through the years before with some minor changes with the help from people outside the brewery through a crowdfunding. In order to not let people down because of this, in a generous act, they made their Black & Deep recipe public. That way, they were encouraging homebrewers to brew it at home.

In Legamia, the regional homebrewers association I am part of, we saw it as an opportunity to organize something around that recipe. It was decided that any of us who wanted to give it a go would brew that beer, according to our own possibilities or ideas, and in a few months we would gather to taste the results. This was something that motivated me, especially for two reasons. In the first place, we had never brewed a beer with such a high ABV. And then, it gave me the opportunity to test a new method, reiterated mashing, which can be used to brew this kind of beers.

Black & Deep recipe, published by Drunken Bros Brewery (click to enlarge)

Since this time we already had the recipe (although as you will see we changed it a little bit), our revision of the style was not as deep as usual and it consisted in reviewing the presentation about Imperial Stout that Mikel Muñoz, one of the brewers from Drunken Bros, offered in the Spanish Homebrewers Association Congress in 2019 in Bilbao. From it we learnt a lot of things. One of the most important ones was the fact that in order to get a high ABV they prefer to do it starting with a higher original gravity and less attenuation from the yeast than starting with a lower original gravity and more attenuation.

Before explaining the process of reiterated mashing, I’m going to describe the approach for our recipe. It was very similar to the original recipe, most of the changes were due to the availability of ingredients. Regarding malt grist, and keeping the percentages as close to the original recipe as possible, we kept Maris Otter, roasted barley, Crystal T50 and Crystal DRC. However, we replaced chocolate malt by Carafa I and dextrin malt by chit malt. Also, since the recipe does not specify the type of oats used, we pick naked malted oats for our version.

For hops, as they are only used for bitterness, we used mostly Saphir and some of Northern Brewer, in both cases to finish some open bags we had. Lastly, we picked Sigmund’s Voss Kveik from The Yeast Bay as the yeast, inspired by the experiences with Kveik yeast in this style that renowned homebrewer David Heath shared in the Spanish Homebrewers Association Congress in 2018 in Cadiz. Kveik yeasts are known to be fast fermenters and they are able to tolerate high ABV. They also perform a quite clean fermentation in restrained temperatures, so this kind of yeast seemed like a good choice for this beer.

Voss Kveik, our chosen yeast for this high ABV beer

Once we set up our recipe, it was time to focus in the process we should follow to get such a high original gravity (remember, 1.119!!). As I’ve already stated before, one of the few options we had to reach those numbers was to test the reiterated mashing method. Basically this method consists in performing a first mash, with more or less half of the grains in the recipe and, once it is finished, remove grains and use the wort from this first mash as the mash liquor for the second mash with the rest of the grains. This way we could get a wort with a high original gravity that, after a longer than usual rolling boil, would concentrate even more. To understand the details behind this method I researched about reiterated mashing online. There is not a ton of information about it and, even though other people wrote about it, it seems that Chris Colby is one of the pioneers of this method, at least in the homebrew scale. His articles about it, in his blog (theory and practice of reiterated mashing) and in Brew Your Own (only for subscribers) helped me a lot to plan our process. Based on the information from those articles, I planned the first mash with half of the total weight of the grains, but only with malt base, Maris Otter in this case. Then, the second mash would be with the other half of the weight of malts, the rest of base malt plus special malts. Also, I calculated a 55% efficiency (10% less of our usual efficiency).

Before describing the details of the recipe and process, there were a couple of things I had also to decide. First, water treatment. I wanted to maintain a chloride to sulphate ratio of 1.5, as described in the original recipe, but I didn’t know when to add the corresponding salts to do that. Drunken Bros people recommend to add them in the boil, but we usually add them to adjust mash pH. And in this case we have two mashes, a total mess. In the end I decided to add them in the first mash to adjust the pH to 5.5 as predicted by Bru’n Water and we would see how we treated the second mash.

Secondly, the addition of coffee. In the original recipe a particular amount is recommended, to be added after performing a cold brew for 72 hours. In our case, I decided to keep the proportional amount of coffee for our recipe, performing a cold brew with 50 g (1.76 oz) of freshly grounded coffee. However, after doing some research and reading this article about coffee addition to beer in Scott Janish’s blog, I keep the cold brew for only 24 hours, since it seems that flavor extraction peaks after 16 hours with this technique. Based on that article too, I added another coffee addition after primary fermentation. Other 30 g (1.06 oz) of coffee added directly to the fermenter, half of them coarsely grounded and the other half as whole beans, looking for flavor (grounded coffee) and aroma (whole beans).

Coffee for cold brew, before grinding

Complete recipe and detailed process are described below:

CRICKET BALLS (IMERIAL STOUT, VERSION OF BLACK & DEEP FROM DRUNKEN BROS BREWERY)

MALTS/GRAINS
5.00 Kg (11.02 lbs) (77.3%) Maris Otter (Thomas Fawcett) (5.0 EBC)
0.40 Kg (0.88 lbs) (6.2%) Roasted Barley (1000.0 EBC)
0.35 Kg (0.77 lbs) (5.4%) Carafa I (Weyermann) (900.0 EBC)
0.25 Kg (0.55 lbs) (3.9%) Crystal T50 (Simpsons) (133.0 EBC)
0.20 Kg (0.44 lbs) (3.1%) Chit Malt (Best) (2.5 EBC)
0.15 Kg (0.33 lbs) (2.3%) Naked Malted Oats (Simpsons) (3.0 EBC)
0.12 Kg (0.26 lbs) (1.9%) Crystal DRC (Simpsons) (300.0 EBC)
HOPS
50.00 g (1.76 oz) Saphir (Queen Country) (4.10% AA) pellets (boil 60 minutes, 34.4 IBUs)
5.00 g (0.18 oz) Northern Brewer (11.20 AA) leaf (boil 60 minutes, 8.5 IBUs)
ADJUNTS
50 g (1.76 oz) freshly grounded coffee, cold brewed for 24 hours. Liquid from cold brew added 10 minutes before the end of the boil
1 teaspoon of yeast nutrients, boil 15 minutes
30 g (1.06 oz) coffee, 15 g freshly grounded and 15 g whole beans, added to the fermenter 48 hours before bottling
YEAST
Sigmund’s Voss Kveik (The Yeast Bay)  (Starter from 1 vial)
THEORETICAL DATA
Volume: 9.00 L (2.38 gallons)    OG: 1.119   FG: 1.046     ABV: 10.0%     IBUs: 42.9     Color: 151.0 EBC     BU/GU: 0.361     Efficiency: 55.00%
WATER PROFILE
Ca: 171 ppm; Mg: 3 ppm; Na: 7 ppm; SO4: 113 ppm; Cl: 172 ppm; HCO3: 120 ppm
MASH
Reiterated mashing (two consecutive mashes)
First mash with 3.25 Kg (7.17 lbs) of Maris Otter and the total volume of water for recipe, 21.41 liters (5.66 gallons). Salts added to adjust pH to 5.5. Keep at 69.0ºC (156.2ºF) for 60 minutes
Second mash with the rest of Maris Otter and all the special malts, using as mash liquor the wort obtained from the first mash. Keep at 69.0ºC (156.2ºF) for 70 minutes
BOIL
90 minutes

Cricket Balls wort before fermenting

As you can see above, due to the huge original gravity, I decided to prepare a starter a few days before brewday. Well, in fact, it was because of that original gravity and because the vial of yeast had passed its date and I didn’t want to take risks. I started three days before brewday. I prepared 600 mL of sterile wort that was transferred to a previously sanitized 2 L flask and then I added the contents of the vial and kept it stirring a couple of days until visible signs of fermentation were observed. After this, I added, in the same flask, 500 mL more of fresh sterile wort and kept it stirring one more day. On brewday, I stopped stirring and left the flask at room temperature so the yeast could flocculate, since in my experience Kveik yeasts (at least the ones I’ve worked with) flocculate in a short time.

The day before brewday, I also grinded the coffee I was going to add at the end of the boil next day (50 g) and put it in a mesh bag. It was coarsely grounded, only to break the beans in a few fragments. I kept the bag with the coffee in a pot with pre-boiled and chilled water (about 500 mL), covered for 24 hours.

Finally, since this time I was not going to have my brother helping me and I wanted to have everything ready, also the day before I prepared all the material needed and crushed the grains. Since I needed to perform two mashes, the brewday was going to be longer than usual. I divided the crushed grains for the first and second mashes this day too.

Cricket Balls, fermenting

When brewday arrived, I was excited to see how this new process was going to work. It was time to start. I added the corresponding salts to the water (3.9 g of calcium sulphate and 5.6 g of calcium chloride) to adjust pH for the first mash and left the chloride to sulphate ratio in 1.52 while water was heating. When water temperature reached 69ºC (156.2ºF) I added the grains for the first mash, 3.25 Kg (7.17 lbs) of Maris Otter, and stirred well to avoid clumps. After a few minutes, and when temperature was stabilized at 69ºC (156.2ºF) I turned on the pump to recirculate wort during this first mash. One hour later, I removed the bag with the grains, trying to get as much liquid from it as I could. To make things easier I put another bag with the rest of the grains for the second mash, keeping the wort from the first mash in the kettle. I stirred thoroughly and heated the mash to achieve the same mash temperature as for the first mash, 69ºC (156.2ºF). I put the lid on the kettle and turned on the pump again so the wort would recirculate. I kept this second mash a little bit longer to help enzymes with conversion. In this second mash, wort became totally black, making the name we have chosen for the beer more than suitable. Also, wort was getting so viscous than sometimes, the pump couldn’t recirculate it and I had to stir well in order for the pump to recirculate wort again. I take a pH reading in this second mash and it had decreased, probably due to the darker malts, to 5.18. Nothing too alarming, but maybe next time it could be a good idea to mix the malts evenly between mashes to avoid these differences in mash pH values. After 70 minutes, I ended the second mash, which had been between 68ºC-72ºC (154.4ºF-161.6ºF) all the time and started heating again to boil as soon as possible, removing the bag with the grains for the second mash.

As in the original recipe, I boiled vigorously for 90 minutes. Half an hour into the boil I added hops to get around 43 IBUs. With 15 minutes left, I added a teaspoon of yeast nutrients and 5 minutes later, I added the liquor from the cold brew to boil for the last 10 minutes. When the boil was finished, it was time to cool the wort with an immersion chiller. It was summer and tap water was not too cool, so when the wort was a little below 30ºC (86.0ºF) I stopped. There were 9.5 liters (2.51 gallons) of wort that were transferred to an 11 liters (3 gallons) PET demijohn, trying to splash as much as I could to oxygenate wort. It was the darkest and more viscous wort I had ever seen. It was time to measure the original gravity and see if my calculations for this reiterated mashing were right or wrong. I couldn’t help to smile proudly when I saw that the hydrometer showed an original gravity of 1.120!!! A point above the theoretical value. I couldn’t be happier. I still had to pitch yeast, but I cleaned everything while the wort cooled a little bit more before doing it. Finally, with the wort at 23ºC (73.4ºF) I pitched the starter, discarding most of the wort from it. This time, fermentation was going to be at room temperature, since Kveik is capable of fermenting at these temperature without off-flavors.

Cricket Balls at bottling

Seven hours after pitching yeast, a good krausen was starting. At the end of the day it was so thick that it reached the neck of the demijohn, with the airlock bubbling like crazy. This first day temperature went from 25ºC (77.0ºF) to 29ºC (84.2ºF). Next day, krausen decreased and temperature went back to 25ºC (77.0ºF). Five days after brewday krausen was gone, but airlock was still bubbling, although slower than the days before. Since I didn’t want to rush things, I forgot about the beer for a few days.

Almost a month after brewday, out of curiosity, I measured gravity. The hydrometer showed 1.038, for an ABV of 11.2%!!! I also took a sample to taste it and the first impression was good. A lot of coffee, alcohol wasn’t overwhelming considering such a high ABV and mouthfeel was great. Things looked good so far. Three weeks later, we proceeded to bottle the beer (this time with the help of my brother again). A couple of days before bottling, I added another 30 g (1.06 oz) directly to the fermenter, inside a mesh bag. Half of the coffee beans were coarsely crushed and the other half remained as whole beans. This dry-beaning was going to impart flavor and aroma for 48 hours.

At bottling time, we followed directions from Drunken Bros and we added sugar to get a low carbonation (about 1.8 volumes of CO2). We bottled almost 8 liters (2.11 gallons), with 20 33 cL bottles and 2 50 cL bottles. Since brewday, 49 days had passed. A lot of time, but it was worth it. Although I am not a big fan of such strong beers and I don’t known when we will brew something similar, the fact that I could test a new method for this type of beers and that everything went quite well made this brew one of the best experiences I’ve had since I started homebrewing. If you haven’t tried reiterated mashing yet, I encourage you to give it a try, I’m sure you will not get disappointed.

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