The day had come. Until now, through these last years all of our beers had been fermented exclusively with the reliable and classic Sacccharomyces cerevisae, a.k.a. beer yeast. Different strains, yes, some of them even quite peculiar, but always putting fermentation in the hands of the same species. However, the rise of sour beers in recent times made us to rethink the possibility of brewing one of these beers. First thing we had to face was to choose a style, since most of you will know, there are several styles of sour beers. Finally we decided to brew a Gose for several reasons: it is a relatively approachable style, it doesn’t take an eternity to brew and we really like the style, more than other sour beers like Berliner Weisse, Lambic or Flanders Red. Once we chose the style, we thought that we were also going to use some fruit for this beer, since Gose is a style that goes well with fruit and it is not unusual to see Gose beers brewed with different fruits. We decided we were going to use apricots this time, so the first thing we did was to buy some ripe apricots during their season. Then we made a purée with them and kept that purée in the freezer while we kept on reading information about the style and how to brew it. Since we brewed this beer in December 2017, the apricot purée spent 3 months in the freezer.
First, as always, some notes about the style and its history. Gose is a pale wheat beer, top fermented and acidified via lactic fermentation. Sodium chloride (table salt) and coriander seeds are used as flavourings. It is usually brewed with barley malt and wheat, with the latter in a greater proportion in the grain bill. Gose was probably once a spontaneous fermented beer and sourer than today versions. The website of Ritterguts, the oldest brewery which still brews Gose contains some useful information about the style and you can even watch an interview where people from the brewery explain how they brew their Gose.
Taking about its history, Gose maybe is one of the most interesting beer styles. I’m not going to detail it because some of you maybe aren’t interested in reading stories about beer. But for those of you who, like me, enjoy reading about the evolution of beer styles, nobody better than the excellent beer historian Ron Pattison to tell you about the history of Gose. However, I’ll give you some notes: first Gose was brewed in the beginning of the eighteenth century in Goslar, in the north of Germany, and it became famous in the next years in the nearby city of Leizpig, where at the end of the nineteenth century it was considered the local beer style. During the twentieth century its popularity declined, to the point that it almost disappeared. There was a revival in the 90s and now you can see how it turned out in your favourite bars.
Focusing on brewing, first thing we had to think about was how we were going to acidify (lower the pH value) of the wort. One of the common ways to do this is to work with lactic acid producing bacteria like the ones from the Lactobacillus family, since they are easy to work with and they are not hard to get, as pure cultures or from the environment since they are present in most of the base malts. If you want to get a fast acidification, there are basically three methods to do it: acidifying in the mash (sour mashing), in the ketlle (kettle souring) or in the fermenter (sour worting). Each one has its own tips and characteristics to avoid troubles and if you want to learn more you can visit this entry from the Sour Beer Blog, where you can find a detailed description of each method as well as some tips to do it right.
We chose kettle souring, I’ll explain the process later. We chose it for several reasons: it’s quick, it’s safe since it avoids cross contamination and it’s easily adjustable.
Before getting into specifics about the process we followed, you can see below a description of the ingredients we used as well as a little summary of the steps of the process. The final volume was 5 liters (1.32 gallons), since everytime we try a new thing we like to start with small volumes.
GOSE WITH APRICOTS
0.60 Kg (1.32 lbs) (57.1%) wheat malt (Grannaria) (3.9 EBC)
0.45 Kg (0.99 lbs) (42.9%) Pilsen malt (Dingemans) (5.0 EBC)
2.50 g (0.09 oz) Hallertauer Tradition (6.70% AA) leaf (boil 45 minutes, 8.1 IBUs)
3.00 g (0.11 oz) table salt (sodium chloride) and 3.00 (0.11 oz) g coriander seeds (boil 10 minutes)
1.00 Kg (2.2 lbs) ripe apricots. Added in the form of purée (previously frozen) in secondary
BACTERIA / YEAST
Fast Souring Lacto (Giga Yeast #GB110) (Gold Pitch, pitched directly). Fermented for 48 hours between 30-40ºC (86-104ºF) until pH was 3.55
Safale K-97 (1 sachet, previously rehydrated). Fermented after boiling and cooling after Lactobacillus ferementation. Fermentation temperature around 19-20ºC (66-68ºF)
Volume: 5.25 L (1.39 gallons) OG: 1.041 FG: 1.008 ABV: 4.2% IBUs: 8.1 Color: 7.2 EBC BU/GU: 0.197 Efficiency: 65.00%
Ca: 111 pm; Mg: 3.4 ppm; Na: 7.4 ppm; SO4: 132 ppm; Cl: 140 ppm
4.86 L (1.28 gallons) water at 64ºC (147.2ºF) for 60 minutes, mash out at 75ºC (167ºF) 10 minutes adding 3.5 L (0.92 gallons) of boiling water
Ingredient selection was easy. For grains, following tradition, wheat malt and Pilsen malt, with the first in a greater proportion. This time wheat malt was from Grannaria, a malting plant in Leon that has increased the grains in its catalog this year. We bought from them because we liked the result we got with our Smash L&G. Pilsen malt was from Dingemans. The little amount of hops we needed came from Germany, Hallertauer Tradition. We also added as adjunts, also following the style guidelines, salt from Añana and coriander seeds, freshly crushed, both in the boil. To acidify we used Fast Souring Lacto from Giga Yeast and to finish fermentation a German strain from Fermentis, Safale K-97, a clean ale yeast.
In the process, new for us, we followed again the advice from the Sour Beer Blog to avoid growth of unwanted microorganisms and/or contamination with Lactobacillus in the cold side of the process. The steps to follow to avoid complications start after mashing. At this point, you boil the wort for 15 minutes to sanitize and kill as many microorganisms as you can. Then, you cool the wort until it reaches around 40ºC (104ºF), a suitable temperature for Lactobacillus (it depends on the strain), and you add enough phosphoric acid or lactic acid to lower the pH to a value of around 4.5. After that, you pitch Lactobacillus and let it ferment, trying to keep the temperature in a suitable range, around 30ºC-40ºC (86ºF-104ºF). It is also advisable to keep oxygen apart, so it is a good practice to purge with CO2 when pitching Lactobacillus to avoid some undesirable byproducts. Finally, when the wort reaches the pH value you are looking for, you boil it as if it were a normal wort for the time you want, adding the hops you want and from then on you keep on as you would do with other beers. Following these steps, you practically avoid growth of unwanted microorganisms, off flavors and contamination of your equipment with Lactobacillus in the cold side of the process.
With all of the above in mind, we started adding enough calcium chloride and sulfuric acid to obtain the water profile showed above, as well as the desired mash pH (theoretical mash pH=5.33). This time we had collected water the day before brewday and we left it overnight so the chlorine could evaporate. After heating water and adding the crushed grains, the initial mash temperature was about 64ºC (147.2ºF). One hour later, after mixing the grains a couple of times, the temperature was a little above 61ºC (141.8ºF). We added 3.5 liters (0.92 gallons) of boiling water for a mash out temperature of 75ºC (167ºF). Before pitching Lactobacillus, we removed grains and we boiled for 15 minutes to sanitize the wort. Fast Souring Lacto from Giga Yeast has a fermentation temperature ranger of 20ºC-37ºC (68ºF-98.6ºF), so we cool the wort to about 40ºC (104ºF) and we added 4 mL of 80% lactic acid to get a pH of 4.68 (we didn’t want to go too far). All of this inside the kettle, where we pitched the Fast Souring Lacto, purging with CO2 at the same time to avoid oxygen. We finally pitched with wort at 39ºC (102.2ºF) and after we put the lid on, we put the kettle in our little fermentation chamber with the temperature set at maximum, 24ºC (75.2ºF),to keep it as warm as possible. The original gravity at this point was 1.033
Next day, 21 hours after pitching Lactobacillus, the pH value was 4.50. The kettle had lost temperature, so we heated it until the wort reached again 40ºC (104ºF) and we put it again in the fermentation chamber, this time with a towel around it to try to avoid heat loss and facilitate the growth of Lactobacillus. A day later, 48 hours after inoculation of Lactobacillus, the pH value was 3.55, just in the middle of the recommended range (3.3-3.8), so we proceeded to boil the wort. Pre-boil gravity was 1.029, giving an attenuation of 11.8%. The theoretical value for this culture described in the Giga Yeast website is 15% fermenting at 37ºC (98.6ºF) for 48 hours, so having into account that our average temperature was lower than that, it was not bad at all.
We added hops 45 minutes before the end of the boil, and the last 5 minutes we also added 3 g (0.11 oz) of salt and 3 g (0.11 oz) of freshly crushed coriander seeds. When the boil was finished, we cooled the wort until it reached 20ºC (68ºF) and we pitched Safale K-97 looking for a clean fermentation, setting the fermentation chamber at 18.5ºC (65.3ºF).
23 hours later a considerable krausen was present and it made us forget about our fears of the yeast not being able to work with a low pH value. After three days, the krausen was gone and fermentation seemed to be reaching its final stages. Nevertheless, we left it another 3 days before adding the apricot purée that we had kept in the freezer for three months. Obviously, we kept it outside of the freezer a few hours so it was a little below room temperature when we added it. Final gravity was 1.008, for 4.2% ABV. Before adding the fruit I took a sip and it tasted pretty nice, with a marked but pleasant acidity.
Sugars from the fruit reactivated the yeast, and next day the airlock looked like a volcano, full of fruit, as well as the top of the fermentation chamber as you can see in picture below. After a couple of days and various changes of airlock everything settled down and the fruit started to fall to the bottom of the PET bottle. Twelve days after adding the apricot purée, we transferred again the beer to a smaller PET bottle trying to clear it. Finally, the second day of 2018 we bottled the beer adding enough sugar to get around 2.6 volumes of CO2 in the final beer. We had certain difficulties because there was still a lot of fruit in it and it was difficult to separate it from the beer, even using some cloth filters. We ended up with around 4 liters of beer with about 4% ABV that filled 12 bottles of 33 cL, left at room temperature to carbonate for at least 2-3 weeks.
As a final summary, and before commenting how the beer turned out, something we’ll do in a future post, I must say that brewing our first sour beer was a very interesting experience. We forgot our fears about “bugs” and this sour beer will be followed by others. The steps to avoid complications when brewing this style are not difficult to follow and the possibilities are endless (different yeast/bacteria strains, other types of fruit,…). However, for future elaborations of beers similar to this, we had to think about the way of adding fruit so we can separate this fruit from the final beer. Maybe we can try putting the fruit in stockings or maybe we can brew a bigger volume and give more time for the fruit to settle down at the bottom of the fermenter (this time we rushed everything because we were looking forward to taste the final result).
For those of you who haven’t brewed sour beers yet, we encourage you to forget your fears and do it since, as you can see, it’s not so complicated and you can get good results without having to wait a lot of time. And for those of you who already brew sour beers, we are all ears if you want to share some tips with us.