Blending Sour Beers with the Solera Method
The primary obstacle to dependable home production of perfectly balanced sour beers is limited blending options. Craft brewers capitalize on their size to fill many barrels; they taste and combine these components, allowing them to achieve a beer with their ideal amount of acidity, fruitiness, oakiness, and funky Brettanomyces aromatics. Few homebrewers have the fermenter space to replicate this. Fortunately, the solera method can achieve consistently delicious results using far fewer fermenters.
Rather than blending to taste at bottling, a solera relies on mixing beers of multiple ages together during aging. When a portion is removed for packaging, the volume is replaced with younger beer. The younger beer can be unfermented, fermented, or even soured. In this way, the solera slowly evolves. While barrels are the traditional vessel for soleras, glass or plastic carboys and Cornelius kegs are options as well (with or without adding oak cubes or chips) for small-scale brewers. The risk of a poorly sealed lid on a plastic bucket is too great for me to recommend them for long-term aging.
Technically, the word “solera” only refers to the oldest vessels, while “criadera” (nursery) is the collective name for the younger vessels waiting to refill the solera. If you do not have room for multiple levels, beer from a single vessel can be packaged and then the vessel refilled with fresh beer or wort.
While the solera method is closely associated with the artisanal production of balsamic vinegar and Jerez Sherry, don’t be intimidated! The same concept is at work at the Tootsie Rolls® factory. A portion of each batch of candy is kept in reserve, to be blended into the subsequent batch of candy. Whatever the product, blending in this way improves consistency by flattening variations in the production process and ingredients.
The blend’s average age in years will converge on the inverse fraction of the beer added each year to the total volume. The amount to pay attention to is the new beer added to the fermenter, rather than the amount drawn out for packaging. For example, if you replace half of the beer once per year, the average age at each pull will eventually converge on two years. The same is true if you replace a quarter of the beer twice a year; what matters is the total amount replaced, not the timing. An average age of between one-and-a-half and three years would be a good initial target, but let your palate guide you to what works for your beer and microbes. I created a spreadsheet that calculates soleras’ average ages; it is available to download at: http://www.archive.org/details/SoleraAgingSpreadsheet.
Solera is a more organic way to blend beers, but at its core the process reduces a brewer’s ability to fine-tune. As a result it may not produce beer as perfectly balanced as traditional blending, but it is much easier and allows for more regular packaging of blended beer. Blending multiple beers together at bottling can result in excess carbonation caused by microbes from one component fermenting residual carbohydrates contributed by another; soleras do not require this consideration.
Solera Barrel at Home
Solera Barrel at HomeNathan Zeender, Head Brewer at Right Proper Brewing Company in Washington, DC, and I share two homebrew solera barrels in my basement. A red wine barrel holds a pale lambic-inspired beer and an apple brandy barrel is filled with an orange-hued beer that bears maltiness reminiscent of a Flemish red. The microbes working in each barrel are Bugfarm cultures from East Coast Yeast.
Solera appealed to us because neither had a need for 30 gallons (114 L) of sour beer from each barrel in addition to our other batches. The solera method also means that we do not need to scramble to completely refill the entire volume of a barrel each time, making it an ideal method for homebrewers aging beer in wine or spirit barrels several times larger than their batch volume.
Once a year we pull out 20 gallons (76 L), replacing it with 22-25 gallons (83-95 L) of wort or beer to account for evaporation. We bottle 5 gallons (19 L) of each pull as is, and use the remainder for three experiments with fruits, spices, flowers, dry hops, and blending. Our favorites so far have been: Dry hopped with citrusy hops (i.e., Nelson Sauvin, Mosaic™, and Citra®), infused with Cabernet Sauvignon wine grapes, and straight-up. The payoff for the relatively modest effort of maintaining two soleras is a case of eight different beers for each of us every year.
All About Consistency
On the unique and ever-changing tap list at Cambridge Brewing Co. in Massachusetts, the most interesting beer process-wise is probably Cerise Cassée. It is brewed with the most authentic solera at any brewery of which I am aware. First brewed in 2004 by Brewmaster Will Meyers, this sour brown ale is fermented on cherries in three sets of five wine barrels. It is easiest to explain the process setup if I start at the end; when the beer in the oldest set of barrels is ready to package, a portion is drawn out from each, and blended in a serving tank. Beer from the middle-aged barrels is then transferred to refill the older barrels and beer from the youngest barrels refills the middle barrels in turn. This leaves empty space in the youngest barrels that is replenished with chilled and aerated wort mixed with 100% sour cherry concentrate.
Once the barrels are again full, they are allowed to ferment until the oldest barrels’ contents are ready for the process to be repeated. The beer is fermented by only the microbes now resident in each barrel. Cerise Cassée is worth the effort, with dark fruit flavors galore in addition to the bright sour cherry, a slight acetic bite, and faint yeastiness. Meyers’ article “La Método Solera,” from The New Brewer July/August 2010, is an insightful look at the complete process.
Breweries that age their sour beers in foeders (mammoth vertical oak tanks), like New Belgium Brewing Co. in Fort Collins, Colorado, rarely drain their foeders completely for cleaning. When the brewers at New Belgium blend beer from several foeders to create their flagship sour brown ale, La Folie, at least 10% of the beer is left in each to ensure a vibrant microbial culture. Wort production for the sour beers is squeezed into the tight production schedule of their main brewhouse. To reduce delays in refilling the foeders, they keep a tank filled with the dark base beer (Oscar). While this exact issue does not encumber homebrewers, many of us cannot always brew a batch on short notice. If you keep beer on hand in a carboy it is easy to top-off a solera, or refill when it is time to keg or bottle.
If your goal is consistency, you may need to adjust the base wort/beer from fill-to-fill. The acidity expressed by our apple brandy barrel-aged solera was close to excessive already at the first pull. To help counter this, we mashed the replacement beer a few degrees cooler, and fermented with highly attenuative brewer’s yeast in carboys, rather than refilling the barrel with wort. Conversely, if the beer is not sour enough, feed the solera with wort high in complex carbohydrates (e.g., use a hotter saccharification rest, or add maltodextrin) to provide more molecules unfermentable to brewer’s yeast, but fermentable by lactic acid bacteria. If you allow the solera to age more than a year between pulls and plan to refill with wort, you should add fresh brewer’s yeast along with it to ensure there are enough viable cells to complete the initial fermentation.
Rather than rely on a solera for the entire fermentation for their Gose, Troublesome, Off Color Brewing in Chicago, Illinois blends a clean base with 16-18% highly-acidic beer from a solera. The two solera tanks are held at 114 °F (46 °C), with 85% of the 2.9-2.95 pH beer pulled approximately once every two weeks. The fermentation is completed entirely by Lactobacillus, which produces lactic acid incredibly rapidly when held at such a high temperature. The acid beer removed from the solera is pasteurized and then combined with the remainder of the batch. The brewers allow time for the brewer’s yeast to clean up the fermentables and flavors contributed by the acid beer before bottling. After each pull, the solera tanks are refilled with unhopped 1.020 specific gravity wort produced from Pilsner malt and wheat. Co-founder and Brewer John Laffler related, “The solera method lets us create a nice, consistent acid beer that shows both maturity from the older, longer fermented beer and a quick way to produce the organic acid we need for simple tartness.” This method is a great alternative to sour mashes, which are less predictable and often also impart unappealing flavors in addition to acidity.
The barrels that make up the solera system at Perennial Artisan Ales in St. Louis, Missouri. The solera method is a way of barrel aging beer where each year a portion of the aged beer in the barrel is removed and replaced with fresh beer.
Consistent Inconsistency
While solera is a great method for improving consistency, that isn’t always the goal. You do not need to refill the solera with the same (or even a similar) beer after each pull. Say you’ve grown bored of a few moderately hopped beers sitting in your kegerator: Combine them, and pitch a microbe blend or bottle dregs from a favorite sour or funky beer. Pull and replace from your new solera the next time you have extra beer you think would mesh with the current flavor profile.
St. Louis, Missouri-based Perennial Artisan Ales’ anniversary ale, Anniversaria, is blended via solera. Their goal isn’t to release the same beer each year, but as brewer Jonathan Moxey put it, “create a thread that will run through each year’s release.” Local wine barrels were initially filled with a 100% Brettanomyces fermented (B. claussenii and B. Bruxellensis var. Drie) variant of Aria, their flagship Belgian strong pale ale. After a year, the brewers pulled 40% of the beer for packaging, refilling the barrels with lower gravity spelt-containing wort from Head Brewer Cory King’s side project, Side Project Brewing, which is also in St. Louis, Missouri.
Future pulls may be flavored with dry hops or fruit, but Moxey told me that this would always be done after the beer was removed from the solera because, “Once you put something in [the solera], you’ll never get it 100% out.” While dry hops can provide a wonderful citrusy or herbal counter-point to sour beer, long exposure could lead to unwanted flavors.
Rather than a set of barrels, the brewers at Sante Adairius Rustic Ales in Capitola, California maintain their solera in a single 660-gallon (2,498-L) “oval” oak fermenter. The resulting beer is dubbed “Cask 200,” a reference to the plaque that came affixed to it. As Co-Owner and Brewer Tim Clifford related, the solera concept was initially, “a pure logistical solution.” Their brewing system produces only 200 gallons (757 L), so filling the entire vessel quickly after packaging would be difficult.
The brewers initially filled Cask 200 with a blend of saisons, and pitched their house souring microbes (Lactobacillus and Brettanomyces). The three refills since have each been with saison, but not the same recipe. The trend they have witnessed has been towards higher acidity. Far from being a problem, Clifford says that, “We want people to be able to taste the differences from batch to batch.”
When to Reset
Sadly there comes a time for many soleras when a vessel needs to be drained completely. This can be taxing both mentally and physically. It is easy to become attached to the solera still containing some of the initial batch five or ten years later (after 10 pulls of 50%, less than 0.1% of the original fill remains). Physically, where are you going to move so much beer?
A few situations where the effort is justified include:
1. A fermenter needs to be replaced.
2. A large barrel needs to be moved.
3. Autolysis-related (meaty/rubbery) off-flavors.
4. Acetic acid (vinegar) or ethyl acetate (nail polish remover) aromatics.
Cambridge Brewing Co.’s barrel-fermentation for Cerise Cassée causes trub to slowly accumulate. Refilling with bright beer, for example, by fining, cold crashing, or filtering (in New Belgium’s case), extends the time possible between cleanings. Meyers also blamed beerstone (calcium oxalate) accumulation on the oak for reducing its oxygen permeability, eventually killing aerobic microbes such as Brettanomyces.
Because of the way they were initially stacked, Meyers was unable to remove the Cerise Cassée barrels for cleaning. To remedy this, he blended the beer from the oldest barrels with stainless-steel fermented beer to balance its high acidity. He moved the beer from the younger barrels to a tank to allow him to clean and rearrange the barrels. Meyers then refilled the oldest barrels with the young beer in the tank, and finally refilled the younger barrels with fresh wort.
Conclusion
Depending on your choices, a solera is capable of either improving consistency or creating an ever-evolving unrepeatable blend. The same concept and techniques can be applied to non-sour beers as well (for example, Placentia, California-based The Bruery’s anniversary strong ales — Papier, Coton, Cuir, Fruet, Bois), but requires heightened vigilance to sanitation as spoilage microbes can be introduced on any fill, ruining the solera. For more on the science, process, and artistry of sour beer production in America, read my book: American Sour Beers: Innovative Techniques for Mixed Fermentations (Brewers Publications 2014).
Jonathan Moxey works with the barrels in Perennial Artisan Ale’s solera system.
SOLERA RECIPES
Perennial Artisan Ales Anniversaria clone
(5 gallons/19 L, all-grain)
OG = 1.065 FG = 1.010
IBU = 19 SRM = 8 ABV = 7.6%
Ingredients
12 lbs. (5.4 kg) American pale malt
12 oz. (0.34 kg) Weyermann Abbey® malt (18 °L)
8 oz. (0.27 kg) biscuit malt
6 oz. (0.17 kg) Weyermann Carafoam® malt
5 AAU Nugget pellet hops (60 min.) (0.38 oz./11 g at 13.3% alpha acids)
0.6 oz. (17 g) Liberty pellet hops (0 min.)
White Labs WLP645(Brettanomyces claussenii) yeast
White Labs WLP644 (Brettanomyces bruxellensis Trois) yeast
Step by Step
Single infusion mash at 152 °F (67 °C) for 60 minutes. Boil 60 minutes adding hops per schedule. Chill to 65 °F (18 °C), aerate the wort with filtered air or pure O2 and pitch with a starter of the yeast. Ferment at 70 °F (21 °C) until the kräusen falls. Transfer to a white wine barrel for aging, or age in a secondary fermenter with 1 oz. (28 g) of white wine-soaked oak cubes. Once final gravity is stable, bottle or keg a portion of the batch aiming for 2.4 volumes of CO2. Refill the barrel with wort or beer, repeating the process.
Perennial Artisan Ales Anniversaria clone
(5 gallons/19 L, partial mash)
OG = 1.065 FG = 1.010
IBU = 19 SRM = 8 ABV = 7.6%
Ingredients
6.6 lbs. (3 kg) light liquid malt extract
2.25 lbs. (1 kg) American pale malt
12 oz. (0.34 kg) Weyermann Abbey® malt (18 °L)
8 oz. (0.27 kg) biscuit malt
6 oz. (0.17 kg) Weyermann Carafoam® malt
5 AAU Nugget pellet hops (60 min.) (0.38 oz./11 g at 13.3% alpha acids)
0.6 oz. (17 g) Liberty pellet hops (0 min.)
White Labs WLP645 (Brettanomyces claussenii) yeast
White Labs WLP644 (Brettanomyces bruxellensis Trois) yeast
Step by Step
Place crushed grains in a large muslin bag. Heat 1.5 gallons (6 L) water to 165 °F (74 °C) and place the grain bag into the water. Mash the grains at 152 °F (67 °C) for 60 minutes. After 60 minutes, raise the temperature of the grain bed to 168 °F (76 °C) and hold for 5 minutes. Place the grain bag in a colander and rinse the grains with 1 gallon (4 L) hot water, about 170 °F (77 °C) collecting the runoff. Top off to 6 gallons (23 L) adding the extract. Boil 60 min. adding hops per schedule. Follow the rest of the all-grain recipe.
Perpetuum Sour
(5 gallons/19 L, all-grain)
OG = 1.058 FG = 1.002
IBU = 11 SRM = 4 ABV = 7.4%
Ingredients
5.25 lbs. (2.4 kg) German Pilsner malt
4.4 lbs. (2 kg) American pale malt
15 oz. (0.43 kg) rolled oats
13 oz. (0.37 kg) flaked wheat
10 oz. (0.28 kg) wheat malt
2.75 AAU Willamette whole hops (60 min.) (0.5 oz./14 g at 5.5% alpha acids)
East Coast Yeast ECY01 (BugFarm) or Wyeast 3278 (Belgian Lambic Blend) cultures
Step by Step
Mash at 156 °F (69 °C) for 60 minutes then raise the temperature to 168 °F (76 °C) for 15 min. Boil 75 minutes adding hops per schedule. Chill to 65 °F (18 °C), aerate the wort with filtered air or pure O2 and pitch yeast. Primary ferment in a red wine barrel at 68 °F (20 °C) or another fermenter with 1 oz. (28 g) of red wine-soaked oak cubes. Allow to age in the barrel or on the oak at around 70 °F (21 °C) until you are happy with the flavor, and the gravity readings remain stable from one month to the next. Bottle or keg a portion, carbonating to 2.5 volumes of CO2. Refill the barrel wort or beer, repeating the process.
Perpetuum Sour
(5 gallons/19 L, partial mash)
OG = 1.058 FG = 1.002
IBU = 11 SRM = 4 ABV = 7.4%
Ingredients
3.3 lbs. (1.5 kg) light liquid malt extract
1.5 lbs. (0.68 kg) dried Pilsen malt extract
2 lbs. (0.91 kg) German Pilsner malt
15 oz. (0.43 kg) rolled oats
13 oz. (0.37 kg) flaked wheat
10 oz. (0.28 kg) wheat malt
2.75 AAU Willamette whole hops (60 min.) (0.5 oz./14 g at 5.5% alpha acids)
East Coast Yeast ECY01 (BugFarm) or Wyeast 3278 (Belgian Lambic Blend) cultures
Step by Step
Place crushed grains in a large muslin bag. Heat 2 gallons (7.6 L) water to 169 °F (76 °C) and place the grain bag into the water. Mash at 156 °F (69 °C) for 60 min., then raise the temperature to 168 °F (76 °C) for 15 min. Place the grain bag in a colander and rinse with 1.5 gallons (6 L) hot water, about 170 °F (77°C) collecting the runoff. Top off to 6.25 gallons (24 L) adding the dried and liquid extract while the pot is off heat to avoid scorching. Boil 75 minutes adding hops per schedule. Follow the remainder of the all-grain recipe.
