Brewing a Fruited Berliner Weisse

Among the scores of historic beer styles, Berliner Weisse has one of the more interesting back stories. Like many styles it was for many centuries largely confined to a specific place, the Prussian capital that later became the capital of Germany. Once lauded by Napoleon as the “Champagne of the North”, by the early 21^st century the style had dwindled to a shadow of its former self in its homeland, so much so that a decade ago Berliner Kindl Weisse was the last surviving example of the once ubiquitous style [1]. Happily, the style has experienced a robust revival over the past decade, triggered in no small part by the efforts of American craft breweries like Dogfish Head (Festina Pêche), The Bruery (Hottenroth), and many others. In the past I’ve written about visiting Berlin and tracking down the once elusive style on its native soil (Seeking the Real Champagne of the North – A Visit to Berlin). In this post I’m going to discuss my attempts to capture the essence of this style in a homebrew, albeit one featuring home-grown raspberries.

The acidity in a Berliner Weisse comes almost exclusively from the action of lactobacillus, the bacteria used to ferment milk into yogurt, among other uses. Lactic acid, the major fermentation product of lactobacillus, gives Berliner Weisse its clean, fruity, dare I say yogurt-like tartness. So, when designing a Berliner Weisse, the strain of lactobacillus you use and the manner in which you accommodate fermentation by both lactobacillus and saccharomyces yeast are key decisions, much more so than the recipe itself, which is pretty simple.  So, before getting into the specifics of my recipe let’s look at our choices of microbes and approaches to fermentation.

Genus Lactobacillus

Lactobacillus is a rod shaped, gram positive bacteria. There are many different species of lactobacillus, a handful of which can be found in commercially available lactobacillus pitches. The most common are brevis, buchneri, delbrueckii and plantarum.  Heterofermentative species (brevis, buchneri) produce lactic acid, ethanol, carbon dioxide and a small amount of acetic acid during fermentation, while homofermentative species (delbrueckii) do not produce ethanol or CO₂. Plantarum can switch between the two depending upon the conditions. In a study published in Brew Your Own Magazine, Michael Tonsmeire and Matt Humbard studied the souring effect of four different lactobacillus species at different temperatures [2]. This study showed that brevis and plantarum were more effective at lowering the pH down into the 3.2-3.4 range common for many American sour beers than the buchneri and delbrueckii strains. The latter was particularly ineffective, only dropping the pH to ~4.4, roughly 10 times less acidic than brevis and plantarum. When using the latter two strains, the drop in pH was pretty consistent at temperatures ranging from 86 °F to 108 °F.  Most of the drop in pH happened in the first 18-24 hours of fermentation, after which the rate of souring slows down considerably. Some of the data from this experiment is plotted below. If you are interested in more details you can find this data and more information than you can absorb in a single sitting on the Lactobacillus Milk The Funk Wiki page.

I’m partial to Omega Yeast products and their Lacto blend (OYL-605) contains a blend of brevis and plantarum. Since these are the two strains shown to be most effective at lowering the pH by producing lactic acid, the choice of which species of lactobacillus to use was straigtforward. Note that lactobacillus is highly sensitive to the presence of isomerized acids from hops. Omega recommends avoiding hop additions altogether, while other sources suggest keeping the IBUs at levels below 5 IBU. Some species, like brevis, are a bit more hop tolerant, but even with this strain hop levels should be kept below 10-15 IBU.

Souring Methods

Lactic acid alone cannot fully ferment your wort. Even the heterofermentative strains produce low levels of ethanol and carbon dioxide. So the next choice is when and how to introduce the saccharomyces needed to finish the job. There is no shortage of options and opinions on the best the approach to using these two bugs together.

Most American craft breweries add lactobacillus after mashing and let it do its thing over the course of 1-2 days before bringing the now acidified wort up to a boil to kill the bacteria. After the boil, the wort is cooled down, saccharomyces yeast is pitched, and standard fermentation follows. Because souring is done in the boil kettle this approach is called kettle souring.

An approach used by some Berlin breweries, including Radeberger when they brew Kindl Weisse, is to split the wort following mashing. Half of the wort is brought to a boil, dosed with a minimal charge of hops, and then fermented with saccharomyces yeast. The other half, which undergoes neither boiling nor hop addition, is soured with lactobacillus delbrueckii. After the yeast completes primary fermentation the two batches are blended back together [3]. This approach may have grown out of old processes involving sour mashing, whereby lactobacillus that lives on the skins of grain are enlisted to do the souring.

The final approach, mixed fermentation, is probably the closest to historic methods of producing Berliner Weiss (although processes varied over time and from brewery to brewery). The saccharomyces and lactobacillus are pitched and allowed to ferment the wort together, a process that continues even after packaging. While this sounds straightforward, there is considerable debate about the timing of adding the two microbes. Because lacto tends to prefer warmer temperatures for fermentation many people prefer to pitch it first to get a head start, and then once the desired degree of sourness is achieved the wort is cooled further and saccharomyces is added.

The main advantage of kettle souring is to avoid exposing your fermentation vessels to live bacteria; a legitimate concern among commercial brewers who want to avoid contamination that would lead to unintentional souring of subsequent batches of clean beer. On the homebrew scale this is less of a concern in my opinion. I have a glass carboy that I use for making sours, while most of my clean beers are fermented in a stainless-steel vessel. Another issue with kettle souring is the challenge of limiting the amount of oxygen available to the lactobacillus during its active stage, which can lead to unwanted off flavors. I do have a lid for my brew kettle, but it hardly makes an airtight seal. For these reasons I ruled out the kettle souring approach. Since the split wort method seems unnecessarily complicated, by the process of elimination I landed on the mixed fermentation method.

When considering the details of the mixed fermentation I was discouraged to find rather contradictory advice about the timing of the lacto and saccharomyces pitches in two of my most trusted reference works. In Jeff Alworth’s “The Secrets of Master Brewers” Alan Taylor, owner and brewer at Portland’s Zoiglhaus, suggests pitching lactobacillus first and holding at 110-120 °F for up to a week before cooling down to 68 °F, then pitching an altbier yeast strain [4]. In sharp contrast, Michael Tonsmeiere warns the reader against pitching lacto first unless you are prepared to monitor the pH in his book “American Sour Beers” [5]. This advice is based on worries that the acidic environment created by lacto will stress the saccharomyces and lead to unwanted off flavors. I opted for a compromise of these two approaches, by giving the lacto a 48 hour head start on the saccharomyces. In light of the aforementioned study by Tonsemeire and Humbard [2], I figured holding the temperature at 85 °F would be appropriate for the lactobacillus brevis and plantaram that make up the Omega blend.

To Brett or Not to Brett

The final question is whether to add brettanomyces to the fermentation mixture. Berliner Kindl Weiss does not contain brett, but analysis of beers from the first half of the 20^th century have consistently found brett in old bottles of Berliner Weiss. Brett advocates include the likes of Ulrike Genz of Berlin’s Schneeeule Brauerei, who makes beers many consider to be the most authentic revivals of the style, and Zoiglhaus’s Alan Taylor. When The Bruery was still brewing and distributing Hottenroth (maybe they still are, but I haven’t seen it for some time), they used a mix of brett and lacto for the primary fermentation, eschewing saccharomyces altogether. I’m a fan of the funky, fruity by-products of brett fermentation, so I’m fully on board with throwing some brett into the mix.

When it expresses itself in a good Berliner Weiss, brett brings fruity accents to the party rather than full on goaty, barnyard flavors.  It does so by driving reactions between alcohols and acids to produce esters. When ethanol reacts with lactic acid it produces ethyl lactate, a molecule whose aroma is reminiscent of coconuts. Brett can also catalyze reactions between ethanol and acetic acid (the main component of vinegar) to produce ethyl acetate, an important component of wine that in low concentrations imparts pear and apple aromas. Analysis of Berliner Weisses fermented with and without brett show ethyl acetate and ethyl lactate levels that are 5 and 20 times higher when Brettanomyces is present [4]. 

Brewing and Fermentation

I have a small patch of raspberries in my yard, and the crop I harvest from that patch is the centerpiece of the beer. In the late summer/early fall when the berries start to ripen I pick them every day or two, rinse them, eat a couple and then immediately freeze the rest. After primary fermentation is done I pull the raspberries out of the freezer to thaw, and then add them to the secondary. Otherwise I’ve tried to keep the recipe and procedure pretty close to my understanding of a traditional Berliner Weiss.

Water – I measure out 3.2 gal of mash water and 4.7 gal of sparge water. I split a Campden tablet (potassium metabisulfite) between the two to remove any traces of chlorine in the water. The water in Columbus, OH where I live is pretty soft, so I add some salts to boost the calcium content and come a little closer to the water profile in Berlin. I add ¼ teaspoon of gypsum (CaSO₄∙2H₂O) and ¼ teaspoon hydrated calcium chloride (CaCl₂∙2H₂O) to the mash water and ½ teaspoon of each to the sparge water.

Ingredients

• 4 lbs      Bestmalz pilsner (47%)
• 4 lbs       Malted white wheat (47%)
• 0.5 lbs   Acidified malt (6%)
• No hops
• Omega Lacto Blend (OYL-605)
• Omega Brett Blend 2 (Bit o’Brett, OYL-211)
• 3 lbs home grown raspberries

A 50:50 mix of pilsner and malted wheat is pretty standard for the style. The acidified malt is a new twist from my first attempt at brewing this beer. From what I’ve read a lower mash pH can help with head retention, which is always a challenge for sour beers. Because lactobacillus is so hop sensitive, I avoid the use of hops altogether.

Wort Production – I heat my strike water to ~165 °F, upon addition of the malts the temperature drops to ~148 °F. I hold for roughly 30 minutes. Next, I pull roughly 1/3 of the mash (~1 gallon) out of the mash cooler and heat up to boiling for ~10 minutes, to simulate a decoction mash. When I add the boiling mash back to the tun, the temperature rises to ~156 °F. I hold for another 20 minutes before running a vorlauf and then sparging with 175 °F water. This produces approximately 6.0 gal of wort with a gravity of 1.034.

To sterilize the wort, I bring it up to a boil for around 5 minutes and then turn off the burner. I’m trying to avoid coagulating a hot break to retain the bready character of the malts. Visually it seems like mission accomplished. I cool with an immersion wort chiller down to about 95 °F, then transfer to a sterilized glass carboy with minimal splashing (I want to minimize oxygen in the wort for the bacteria). At this point I’ve got 5.5 gallons of wort with a gravity of 1.036. The very short boil and lack of any hop additions makes for a fairly easy brew day.

Fermentation – I pitch a package of Omega Lacto Blend (OYL-605) straight from the package (no starter) and wrap a heating pad around the carboy. I set the controller to hold at 85 °F. After 36 hours I cut the power to the heating pad and let the wort cool. In the meantime, I make a 2 quart yeast starter for a package of Omega Brett Blend #2 (Bit o’Brett, OYL-211). This blend contains two strains of saccharomyces, one brett-famous Coloradao brewery strain (Crooked Stave?) and one strain formerly classified as brett (Sacch-Trois?) along with brettanomyces bruxellensis. It seems like the fermentation character of this yeast blend would make a good complement to the lacto. After allowing the beer to cool down to 72 °F, now 48 hours after the lacto pitch, I pitch the entire sacch/brett starter.  

The next day there’s a healthy krausen on the beer and vigorous airlock activity. After two days the krausen drops, but there is still a bubble coming through the S-shaped airlock every 1-2 seconds.  Five days after pitching the yeast the bubbles have slowed to 1-2 every minute and the gravity reads 1.009. The beer is straw colored and very hazy. The taste is more tart than sour and quite bready, presumably from the proteins remaining in the beer. At this point I add 3 lbs of homegrown and thawed raspberries to the carboy. Since it’s a sour beer I don’t do anything to kill any bugs living on the raspberries. The fruit addition kicks off steady bubbling in the airlock for the next 24 hours or so. The photo below shows the carboy before and after adding the raspberries.

Packaging – Eight days after adding raspberries to the secondary I’m ready to bottle the beer. The final gravity is 1.008, which translates to 3.7% abv and an apparent attenuation of 78%. I transfer ~5.2 gallons of beer to the bottling bucket where I mix with a solution of 6.9 g table sugar. Since high carbonation is a hallmark of the style, I’m targeting 3.5 volumes of CO₂. Most of the beer goes into thick walled 500 mL bottles.

Note – The first time I made this beer I used dried ale yeast, Lallemand BRY-97 West Coast Ale Yeast, and the dregs from a bottle of Orval. The attenuation was similar (O.G. = 1.030, F.G. = 1.008), but the lag time before I saw any yeast activity was 36 hours. Despite the consternation that the long lag time triggered, the finished product had a very clean acidity, though there was relatively little brett character.

Tasting Notes

Just over a month has passed since bottling, so let’s see how the beer turned out. The beer is a striking pinkish-red hue that reminds me of ruby red grapefruit juice, hazy rather than clear, enthusiastically effervescent, topped by a lovely 2-3 fingers of snow-white head. Achieving good head retention in a Berliner Weisse is a challenging feat, but this beer passes with flying colors. It takes a good 5-10 minutes for the head to recede, finally settling on 1-2 mm scrim that persists until the glass is empty.

The aroma is tart, not unlike plain yogurt, with an underlying fruity character that has a raspberry note.  The tangy, clean acidity of lactic acid dominates the taste of the beer. The acidity goes beyond tart but stops short of bracing. As someone who enjoys a good sour beer, I’m satisfied with the level of acidity, but for more casual drinkers, like my wife, it might be a little too much. Once I move beyond the acidity, I begin to pick up some fruity notes in the background. Interestingly, they skew closer to lemon than raspberry, although as the glass empties and the beer warms I think I might be picking up some raspberry character. It’s hard to say for sure, the red color might be playing tricks on my senses. I’m happy to report there are no undesirable off flavors to be found. The combination of a light body and prickly carbonation makes for an almost airy mouthfeel.

Overall this is a clean, refreshing thirst quencher. I couldn’t be happier about the appearance, the pinkish-red hue and voluminous snow-white head make for a lovely beer. The absence of off flavors is a sign of good brewing technique; apparently adding the saccharomyces 48 hours after the lactobacillus doesn’t lead to any issues with the yeast fermentation. I’d like to see a little more complexity in the beer, and it’s possible that with 6 months or a year in the bottle the brettanomyces will start to do its thing. I’d also like to see more prominent raspberry flavors. I guess I’ve got to up my gardening skills next year and shoot for a harvest that is closer to 5 lbs than it is to 3 lbs. 

Lessons Learned

What have I learned about brewing a fruited Berliner Weisse? I’m happy to report that the Omega lacto blend is perfectly capable of souring the beer in 2 days at 85 °F. Perhaps more importantly letting the lacto get a head start does not lead to problems with the saccharomyces fermentation, either with the Omega Bit o’ Funk blend or with the Lallemand dry yeast. Secondly, the head retention was noticeably better the second time around, presumably from the addition of some acidulated malt to lower the starting pH a little. If anything, the finished beer was just a bit more sour than intended. Next time I brew this beer I’m tempted to cut down the lag time between pitching the saccharomyces and the lactobacillus or even to cool the wort to the mid 70’s and pitch them together. A more measured tweak in the procedure would be to pitch the lacto at 85-90 °F as before, but let it cool naturally for the next 24 hours before pitching yeast. As for getting a more complex sour character, perhaps all I need is a little more patience. After all, one wouldn’t expect brett to do much after only one month in the bottle. I’ll report back in the comment section in 6-12 months on how the beer evolves with age. If others have suggestions for increasing the complexity of this style, I’d love to hear them. It’s also possible that I’m expecting too much complexity from this style. Maybe that’s the point of adding fruit to the beer, to add complexity to what is otherwise a bit of a one note beer.

I will say that if you are going to miss your acidity target, I’d rather be a little too sour than not sour enough. This beer would be an excellent candidate for a raspberry syrup addition like they do in Berlin. It also makes an excellent mimosa-like drink when mixed with orange juice. Maybe that’s as close to the tag “Champagne of the North (Clintonville)” that I can expect.

References

[1]. In his book “Brewing with Wheat” Stan Hieronymus reports that the number of weisse breweries in Berlin increased from sixteen in 1879 to forty seven in 1892 to seventy one in 1897. This number dwindled down to two by the end of the 20^th century, Kindle Weisse and Schultheiss. In 2006 Schultheiss was purchased by Radeberger, the brewery that makes Kindle Weisse.

[2] Michael Tonsmeire and Matt Humbard, “Brewing with Lactobacillus” Brew Your Own.

[3]. Stan Hieronymus, “Brewing with Wheat: The Wit and Weizen of World Wheat Beer Styles” Brewers Publications, Boulder, CO (2010).

[4] Jeff Alworth, “The Secrets of Master Brewers” Storey Publishing, North Adams, MA (2017).

[5] Michael Tonsmeire, “American Sour Beers” Brewers Publications, Boulder, CO (2010).