If you wanted to boil the entire enterprise of modern brewing down to a reasonable definition, it would be this: activities meant to rid breweries of wild yeast and bacteria. The first great innovation in brewing history was malting grain; the second great innovation was hopping. Then in 1857 Louis Pasteur brought brewing into modernity when he described the process not just — or even primarily — of fermentation but the process of infection. That was the third and final innovation.
Here’s how he put it in Etudes sur la Bière (Studies on Fermentation): “How is it that the use of ice and yeast operating at a low temperature [in lager brewing] so greatly facilitates the preservation of our beer and enables us to secure such striking advantages? The explanation is simple: the diseased ferments, which we have pointed out, rarely appear at a lower temperature than 10°C [50°F] and at that temperature their germs cease to be active.”
Wild brewing — the activity of courting feral yeasts and bacteria and trying to harness them to produce something tasty — is a remnant of the time before Pasteur. It is a weird and dangerous activity, and more than a few commercial breweries have failed to corral those wild yeasts and keep them out of nonwild beer. For the homebrewer, however, it’s nowhere near as risky. We often brew alfresco anyway, so there’s no real brewery to infect. If you do find your porter has taken on a musk, it’s cheap and easy enough to dump the plastic and rubber parts of your equipment and replace them. And since homebrewers are by nature curious, it is a wonderful way to run some fascinating experiments.
Wild brewing — the activity of courting feral yeasts and bacteria and trying to harness them to produce something tasty — is a weird and dangerous activity.
There are a couple of downsides. Commercial-scale wild brewing still does exist in parts of Belgium and Germany (and, increasingly, in the United States), but makers of lambic and tart Flanders ales rely heavily on vat aging. Nature-inoculated beers take a long time to develop, and they require the presence of low levels of oxygen to sustain their microbiomes. Wood is porous, and oxygen slowly seeps into the beer — a critical ingredient to the development of wild ales. Furthermore, it’s not just the presence of oxygen, but the right amount of oxygen. Wine barrels, with their thin staves and large surface area, expose beer to more air than large vats with thick staves and a smaller volume-to-surface ratio. (See Barrel Aging for more.)
As a consequence, the practices of breweries making wild ales are the least adaptable to the home brewery. Rodenbach has tuns as large as 65,000 liters (over 550 barrels, or 17,000 gallons); lambic makers regularly use foeders 10 times the size of a wine barrel. Even if you bought a wine barrel and managed to fill it with wild-inoculated beer, it would be difficult to manage because wine barrels are so small by comparison (though Cantillon ferments and ages in wine barrels). Anything smaller will just expose the beer to too much oxygen. For small-scale projects we have to look elsewhere, using the wisdom of the old masters only as a guide. Fortunately, there are a few work-arounds.
But before we get to those work-arounds in the following chapters, let’s consider wild ale. What exactly are we talking about? There’s a nebulous category that runs the gamut of everything from Berliner weisse and gose to lambic. The tart ales of Flanders, funk-tinged saisons, a catchall category of “wild ales,” obscure or mostly obsolete styles such as Lichtenhainer and Münster altbier (never mind adambier and jopenbier) — all of these have either been ruled in or out of the group from time to time. For the purposes of this book, let’s think of wild ales as having these characteristics.
Wild yeast. There’s a whole category of beer made with acidification by Lactobacillus. Lactic fermentation can be conducted with laboratory yeast within a few days (see Kettle Souring). It produces a clean, citrusy tartness. It’s a reliable way to make a beer, one that’s reproducible batch after batch. Let’s exclude this kind of beer from the mix. For a truly wild ale, wild Brettanomyces must be present. During alcoholic fermentation, Brettanomyces produces an entirely different flavor profile, one more complex and varied. It is responsible for that unexpected balsamic note in tart Flanders ales and the tropical fruit notes in lambics. It can also give a beer a dry, leathery quality along with that famous “barnyard” funkiness, and even produce acetic acid. All of this is categorically different from the flavors you get from a lactic fermentation.
Long maturation. As Crooked Stave’s Chad Yakobson has ably demonstrated, Brettanomyces is capable of producing fairly straightforward primary fermentations. We’re more interested in what Brettanomyces does after many months — or a few years. Brettanomyces has the capacity to consume sugars that regular Saccharomyces cannot, and in the long period of activity, it continues to produce those flavor compounds that increase the complexity of a beer. Young wild ale — lambic, say — tastes markedly different before it ages, thanks to this process of slow maturation. It’s a flavor profile that can’t be imitated by other processes or sped up.
Natural inoculation. Pitching a strain of Brettanomyces and letting it work on a beer for a couple of years is adequate to meet the definition of wild ale. But if the beer is inoculated naturally through ambient yeasts and bacteria (spontaneous fermentation), it definitely is. As we’ll see in chapter 26, there’s a reason to try to use nature to inoculate your beer. Each location on the planet has a unique mix of yeast and bacteria, and those organisms express themselves in the beer. Spontaneous beer made in Portland, Maine (Allagash) doesn’t taste like the stuff made in Tillamook, Oregon (De Garde); Dexter, Michigan (Jolly Pumpkin); or Brussels (the lambic breweries).
There are only two chapters in this section, and the first, Tart Flanders Ales, describes the process of using laboratory-cultured wild yeasts and bacteria. This chapter contains a discussion about the process of making a beer like those of Rodenbach or Verhaeghe, but it applies more generally to pitched “wild” cultures. The second chapter, Spontaneous Ales, describes different ways to work with natural inoculation, aging, the use of fruit, and blending.
The northern and especially western part of Belgium has long been the home of brown ales. Although pale beers have slowly made incursions into the market for these ales, they are still common there, and some of the most famous — Westvleteren, St. Bernardus, Rodenbach — are still under healthy production. Even new revivalist breweries like De Dolle and De Struise have taken up the tradition. For the most part most of the modern brown ales are no longer kissed by wild yeast, but there are a few exceptions. Rodenbach, Verhaeghe, Liefmans, Bockor, and others continue to make round, fruity, and, in particular, tart brown beers like their ancestors did.
Efforts to replicate these beers outside Belgium have largely been failures. Getting the right balance among the elements is difficult, and many American results have been punishing rather than pleasant. In Belgium the beers are wood-aged, and many use yeast strains once obtained from Rodenbach, which used to spontaneously ferment its beer. The elusive balance they achieve rests on a triangle of flavors: rich with fruity esters, a bit sweet, and tart with an acidity that often presents as a distinctive balsamic note.
They are sometimes known (thanks mainly to the writer Michael Jackson) as the “Burgundies of Belgium,” and while there’s no mistaking them for wine, there is something in the balance of the elements that evokes their deep, vinous flavors. (And if you ever have a guest over who believes he doesn’t like beer but loves red wine, hand him a bottle of Verhaeghe’s Duchesse de Bourgogne and smile.) These beers are very hard to replicate at home, but it can be done — if you know a few of the key secrets of “mixed fermentation.”
Josh Pfriem (rhymes with “team”) is one of the most methodical brewers I’ve ever met. A native Seattleite, he fell in love with good beer while he was studying business marketing in college. That love led to homebrewing, and homebrewing led to an epiphany. “After that first batch of homebrew, I knew I wanted to open my own brewery and be a brewmaster.”
He stuck with the business marketing major, but after graduation pursued brewing. He started at Wasatch Brewing (Utah), then moved to Chuckanut (Washington), and finally ended at Full Sail (Hood River), learning at each stop. Because of the laws in Utah, he learned great discipline making flavorful low-alcohol beers at Wasatch, then learned how to make high-quality, balanced lagers at Chuckanut. Finally, he felt he needed to understand large-scale production brewing, which made Full Sail a good capper to his on-the-jobs brewing education.
Despite this varied experience, the beers of Belgium exerted a special gravitational pull on Pfriem’s interests. Before starting at Chuckanut, he and his wife spent several weeks touring the country on their bikes. “To experience those beers fresh, the vibrancy, the finesse, how well the beer paired with food — it was amazing.” When he opened pFriem in 2012, he already had a strong idea of the kinds of beers he wanted to make — European, food-friendly beers with an accent on Belgian styles.
But even more, he knew he wanted to make slow, barrel-aged beers like those he tried in Brussels and Roeselare. From the very start his vision for pFriem Family Brewers included a barrel-aging program, and some of his first batches were beers that would become lambic-style and Flanders-style tart ales. When he debuted Flanders Red two years after the brewery opened, he told me, “These are the beers I founded the brewery to make.”
Despite the fact that this was their maiden release, pFriem Flanders Red is one of the most accomplished examples of this type of beer made outside Belgium. It captures that rare triangle of flavors — esters, acidity, and sweetness. I was not surprised to learn that he approached the beer the same way the Belgians did, using mixed fermentation.
People have been trying to catalog the styles of Flanders for a long time. Writing in the 1850s, Georges Lacambre clustered the dark beers of the region together out of convenience, acknowledging that they came “in a number of varieties. . . . It varies greatly from place to place and sometimes in the same locality; often in the same town there are not two brewers whose beers are the same.” The one thing they shared, their color, was actually a proxy for a brewing method: extremely long boil lengths. The standard was 10 to 12 hours for the famous beers of Mechelen, and in West Flanders they were longer — sometimes an astonishing 20 hours.
More than a century later, the writer Michael Jackson divided them into two types: “oud bruins” (Liefmans-like beers) and Flanders red ales (Rodenbach-like). But this is both too expansive and also too limiting. There are some notable differences between these two models, but why stop at just two? Bockor and Van Honsebrouck make brown beers that get their color from lager mixed with spontaneously fermented ale. Bavik makes Petrus, a similar beer that uses brown ale instead of lager. De Dolle Brouwers boil their brown for three hours — echoes of the past — to encourage Maillard reactions.
Verhaeghe and Rodenbach have vinegar/balsamic notes and pure, sharp tartness. Bockor (Bellegems Bruin) has a similar nose but is smoother and lacks the sharp acetic sour of Rodenbach. De Dolle is a huge, deep beer with a dry, austere finish. Liefmans has a sweet-and-lactic-sour character that is less complex but more comforting. Bavik’s Petrus Oud Bruin is woody and bitter but has a nonbalsamic vinegar note that penetrates the palate. These beers are, just as beers of old, different in their own ways. It makes no sense to divide them — as in Lacambre’s day they are all singular ales.
Collectively, they compose a range of beers that have a loose affinity. They use different methods of mixed fermentation and aging to create layered, complex beers that use malt sweetness, ester production, and tart, wild flavors to balance one another. When he approached his own version of this type of beer, Josh Pfriem did not try to emulate a particular example. He used his own New World method of mixed fermentation that borrowed from Rodenbach, added the element of wine-barrel aging, and created a beer with a light acidity, bright cherry esters, and a gentle cosseting of natural sweetness.
It is very much in the vein of the old examples, but not a replica. If you are a homebrewer approaching this difficult style, it’s worth keeping this in mind: your practices and techniques are liable to produce a beer unlike those of Rodenbach or Liefmans — but that doesn’t mean it won’t be authentic. Your goal should be to produce a beer with the triangle of flavor, one that is balanced and tasty, not necessarily a replica of one of the famous brands.
Let’s start with Rodenbach, which by any measure is the undisputed king of the category, and work our way back. Founded just after Belgian independence in 1836, Rodenbach didn’t become the brewery we know until a third-generation family member, Eugène, returned from England, where they were making vat-aged porter. In 1872 he began collecting wooden vats — foeders — to age his beer the way the porter brewers did. Over time the brewery dug out 10 vast cellars underneath the brewery, where 294 foeders now sit. And it is in those cellars — not in the shining, state-of-the-art brewery — where Rodenbach is truly made.
The essence of Rodenbach’s process is this “mixed fermentation” I’ve referenced, and here’s the brewery’s master brewer, Rudi Ghequire, describing it: “In our process we work with a yeast culture with eight different yeast strains and also a little bit of lactic bacteria. During the first week we have an alcoholic fermentation from the yeast cells, and after one week the lactic bacteria take over. During the lagering time [four to five weeks] we reduce the yeast cells in the beer by precipitation, and then we send a nearly bright, young beer to the wood. The big difference between spontaneous fermentation and mixed fermentation is with spontaneous you send wort to wood and we send young beer. Beer has an alcoholic protection, so it is less risky. When you reuse yeast from spontaneous fermentation, you have arrived at ‘mixed fermentation.’ ”
The key here is that Rodenbach brews a beer first, then sends it, fully fermented (and acidified by Lactobacillus), to the wood. This means there’s only limited sugars available for consumption by the wild yeast resident in the foeders. In the two years that beer sits ripening, those microorganisms will both add acidity (pH in the foeders can drop to 3.2) and dry the beer out (some foeders will produce beer that is 98 percent attenuated).
Even more important are the development of fruity esters that give the beer so much of its character. This makes Rodenbach somewhat similar to a Berliner weisse, where the Brettanomyces metabolize acids into esters. Like Berliner weisse, Rodenbach does not have an overtly Brett-like palate; rather, it’s the interaction of the yeast and bacteria that produces the critical esters. After aging, Rodenbach blends aged lots back with fresh, green beer (67 percent aged stock in Grand Cru, 25 percent in regular Rodenbach). The esters harmonize with the young beer to give Rodenbach its balancing sweetness.
Wyeast offers a version of Rodenbach’s complex yeast strain (3763, Roeselare Ale Blend), and many commercial breweries have used it to ferment wort — almost always a disaster. The wild yeasts and bacteria turn the beer into a chemical stew. Josh Pfriem follows Rodenbach’s lead and starts out making a standard beer before adding the funk. He makes a beer that will feed the complex biochemistry to come, not one that tastes particularly good at birth. “None of the beers are attractive to drink before they go into the barrels — they’re sweet and flabby. But that’s what we want. It’s not about what it tastes like going in, it’s what it tastes like at the finish. We do high mash temperatures, and we build some big dextrines and proteins, stuff for the bugs to chew on. It’s a low-IBU, very Belgian-y base to start with.” This is the trick, whether you’re using the Roeselare strain or pitching your own wild yeasts.
Pfriem mixes a precise cocktail of cultures, and he wants only those cultures. Because it’s going on wood, he tries to keep the environment as sanitary as possible (“We treat it like pilsner”), purging the barrels of oxygen before filling them with the beer. “We remove the yeast from the beer before it goes into the barrels, and then we’re inoculating with a culture of Lactobacillus, Pediococcus, and Brettanomyces.” Wyeast grows it up, and they pitch a blend of the three “at the rate of a liter per wine barrel.” Pfriem doesn’t have the luxury of being able to work with either an old yeast strain that came from spontaneous ferments nor 100-plus-year-old foeders. When you’re working from scratch, you have to add your own bugs.
It’s a very old style of brewing, and understanding these kinds of beer requires thinking differently. Ghequire left me with a coda that can serve as a North Star for making tart Flanders ales. “The production method that we use is conservation by acidification or acidity. You have to go back in time to when people didn’t know the healthy work of hops. They found another method to preserve the beer, and that was conservation by acidity. So they stored the beer on wood, and it became a very acid beer after a period . . . because [in an acidic environment], bacteria don’t grow so fast.”
Josh Pfriem
pFriem Family Brewers
Ferment with Wyeast 3538/3787 or White Labs WLP530/WLP540 at between 65 and 70°F (18 and 21°C). Make sure the wort is well oxygenated (25 parts per million, ideally). Rack beer after primary fermentation, and cold condition for 2 weeks (keeping beer as close to 32°F [0°C] as your equipment allows). The beer should be around 3° P/1.012 at this stage.
Rack to a clean carboy, taking care to leave behind as much flocculated yeast as possible, and let rise to room temperature. Pitch a culture of wild yeast and bacteria: Wyeast 3763 (Roeselare) or 3278 (Lambic blend) or White Labs WLP665 (Flemish Ale) or WLP655 (Sour Mix 1). Let mature for 18 to 24 months.
Bottle-condition only, shooting for 3.5 volumes of carbonation.
Notes: Pfriem suggests treating both mash liquor and wort with a gram per gallon of calcium chloride (CaCl2). Hop type is not critical, so use any low-IBU variety available. If you want to use an actual wine barrel, find a barrel “that has seen at least two turns of wine.” (Wood character is not appropriate to this style.) Pfriem makes his own blend of wild cultures, and you can, too, but lab blends are best as a starting place.
It’s important to start out with a good base beer that has, as Pfriem puts it, “stuff for the bugs to chew on,” but this style really depends on those 18 to 24 months in the carboy. The purpose of wood aging is not only to inoculate the beer but to feed it a slow, steady diet of oxygen. For Pfriem this means leaving his casks alone. “We stay out of the barrels. If you get into it, you’re going to get more [oxygen in]. You’ll develop acetic acid, but we try to keep it as minimal as possible. We want the other microbes to live well.” Wood is the ideal vessel to strike this balance, and Pfriem acknowledges that “it’s hard to make such a dynamic beer without aging in an oak barrel.”
But it’s not impossible. Using wood products is discussed in the Old Ale chapter, though the intention here is different. In the case of wild ales, you’re not trying to add a woody flavor, but make sure that slow drip of oxygen seeps into the beer. I recommend a small amount of oak cubes; they have less surface area than chips or spirals, which means they’ll release oxygen the slowest. Use just 2 ounces, added at the start of aging. You can buy different types, and I recommend a medium French oak. French oak has a less aggressive oaky flavor, and a medium toast will reduce the woody flavors of light toast without getting into the smoky flavors from dark-roasted wood. To further remove some of the flavor-causing oils, boil the cubes for 10 minutes and then let them dry fully before adding them.
Josh Pfriem starts with a standard all-Saccharomyces base beer, but if you want to try something closer to Rodenbach’s process, try the technique described by Matthias Richter in the gose recipe. He pitches a 1:1 ratio of Saccharomyces and Lactobacillus. Use one of the same strains Pfriem recommends (Wyeast 3538/3787 or White Labs WLP530/WLP540) and combine with Lactobacillus (Wyeast 5335/White Labs WLP677), fermenting at 70°F (21°C). You can also use the alternate kettle-souring technique described in chapter 10.
One of the most fondly regarded beers by people of my vintage was cherry-infused Rodenbach, which returned in 2016. Cherry is such a perfect addition because the vinous esters already give a hint of it. Cherry seems to be a natural fit for these kinds of beers — Liefmans (Kriek) and Verhaeghe (Echt Kriekenbier) both make versions of their regular beer aged on cherry.
It’s easy to implement. Choose cherries with rich colors and full taste. Since you’ll be using plenty of souring microorganisms in the beer, you don’t need sour cherries for acidity — though of course they work well, too.
Add whole cherries to the carboy at a rate of half a pound to 1 pound per gallon for the final 6 to 12 months on the wild yeast and bacteria. There’s no need to crush the cherries; the wild yeast will consume them whole. The pits will add an additional layer of tannins, which in these beers has a cinnamon/spice quality, which is itself a great note.
One of the secrets to professional brewing — and a necessity in brewing beers with wild yeast — is blending. Each wooden vessel becomes its own ecosystem, and a batch of Rodenbach that comes out of Foeder 133 will not resemble Foeder 132’s beer, even if they were made from the same base beer. Rodenbach is made by blending many different foeders together into a mother blend that contains the typical elements expected in that beer.
Lambic is almost always blended as well, though with a different goal. When blending lambic for a gueuze or other blend, blenders are looking to create layers and layers of complexity in a beer, not match flavors from previous batches. At Cantillon Jean Van Roy starts by tasting his older lots first. “It depends on my old beer. If I have a mellow lambic with some soft beer, I can work with two- and one-year-olds with mild character. If I have an old beer with [sharp] character, I have to find other types of beer. Each blend is different.”
You have to plan ahead, but blending is a great way to work with homebrew, too. If you have two or more carboys of wild ale, it allows you to compose a beer with the strongest elements of each (while concealing unwanted elements). When blending, think in parts (1 ounce, or a shot glass), and start composing with your different lots. Start with equal blends, and then begin layering in more parts from beers you want to accentuate.
It’s even worth considering keeping a batch of beer around that doesn’t seem particularly good, because in very small amounts it may add a great deal to a blended beer. At Solera Brewery, not far from pFriem, Jason Kahler describes how he adds a hint of acetic acid from an otherwise unpleasant batch. “I really like a touch of acetic acid, and I have a keg of very hard, acetic beer just to top off a beer. Even just 6 ounces of hard beer in 5 gallons can bring out so many different flavors — but not make it taste acetic, either.”
Yeast is everywhere. It lives on, in, and around just about everything on the planet. There are more than 1,500 different species of this single-celled fungus, and their ubiquity made it possible for humans to begin making beer long before they domesticated and started malting grain. In much of the world, people still make rudimentary old beers the way our ancestors did, letting the ambient yeasts and bacteria turn grain-steeped water into traditional beer, such as African umqombothi (from sorghum), South American chicha (from corn), Russian kvass (from rye), and Asian handiya and huangjiu (from rice).
But in the brewing countries of Europe, much safer domesticated yeasts have displaced all but a few tiny remnants of commercial beers made by spontaneous fermentation, and these — all located in Belgium — were on death’s door by the 1990s. Then a funny thing happened. Craft brewers began to rediscover the thrill of brewing with feral microbes, and now there are dozens of breweries openly courting wild yeasts and making a new generation of spontaneous ales. More than a handful are even devoted to making mostly or exclusively spontaneous ales. A couple of decades ago, people weren’t even sure whether it was possible to make these beers outside Belgium, but now we know that not only is it possible but that, depending on a brewery’s location, they can be exceptionally accomplished.
The processes used to make the most famous wild ales — lambics — are beyond the ability of most homebrewers. Those are vat-aged beers, and the smallest vessels they use, wine barrels, are too big for all but the most avid homebrewer. But the basic process of fermenting wild is tailor-made to small-scale brewing and is one of the few approaches where homebrewers can meet or exceed the quality of the pros. Even more alluring, fermenting wild beers at home reflects the terroir of the backyard, meaning that no two of these beers will taste the same.
It’s safe to say that Solera has one of the prettiest locations of any brewery anywhere. When you walk out the back door of the brewery, where picnic tables have been scattered around a grassy field, you stand at the foot of Mount Hood, Oregon’s tallest mountain. Just beyond this alfresco dining room is an orchard of fruit trees, and Hood watches over it like a curious giant. Founder and brewer Jason Kahler could sell cans of Natty Light and people would come just for the view. Remarkably, though, he serves some of the best beer in the United States. Kahler has developed a communion with both wild yeast and the fruit that grows in the surrounding valleys (the latter collects the former), and his wild ales, saisons, and weissbiers bear the mark of this relationship.
Kahler named his brewery after a process he developed as a homebrewer, one borrowed from a technique developed in Spain and Portugal to age wine and sherry. In brewing it’s a method of preserving an ecosystem of wild cultures in a vat of beer. Other breweries also use it (notably New Belgium), but Kahler discovered it accidentally when he was blending his own homebrew. It wasn’t until later that the word “solera” appeared in his vocabulary — and became a regular part of his brewing routine.
Kahler got his start as a homebrewer in the mid-1990s. That led to a job at Fitger’s Brewhouse in Duluth, Minnesota, and then to a more technical education at Siebel. He arrived in Oregon in 2000 to work for a winery, where he became interested in blending. He was still homebrewing, and that was when he began experimenting with the solera project. Eventually he went on to work at Full Sail, Walking Man, and Big Horse, breweries all located in close proximity to Parkdale.
He didn’t get to practice much funky brewing at those breweries, so he continued to do so at home — and it was a central focus of Solera when he founded the brewery in 2012 with John Hitt. Many brewers are gun-shy in the presence of untamed yeasts, but Kahler seems to relish having them around. “You can get Brettanomyces from the laboratory, and you can get Brett from the air,” he says. “I love Brettanomyces, I love Lactobacillus, Pedio. They’re all there in the air; you don’t need to buy them.” And even more: they give Solera’s beer the flavor of the place, a quality of terroir. For a brewery situated where Solera is, it’s an understandable impulse.
Many people think we only recently learned how yeast works, after Louis Pasteur described it in 1857. That’s not entirely true. While brewers didn’t know it was caused by tiny fungi, they understood the mechanics well enough. Any homebrewer will realize why: after fermentation the bottom of the carboy is covered by an inch of white stuff. At Bamberg’s Schlenkerla, master brewer Matthias Trum put it this way: “Zeug, which is ‘stuff,’ was the German word.” He added that managing the zeug was even a job at the brewery, handled by the hefener (yeast man). “The hefener’s job was to harvest the yeast from the batches, to press out as much remaining beer as possible, which was sold at a low price to the poor, and then the yeast was added to the next batch.”
So even hundreds of years ago, making a beer without adding yeast was unusual. Brewers used a device called a coolship — a broad cooling pan — to cool hot wort. Most breweries used it in conjunction with such other devices as drip chillers, and they pitched their yeast as soon as they could get it to the right temperature. But lambic makers in the region near Brussels left it in the coolship overnight and in the morning transferred it straight to vats, where it would slowly ferment and ripen over the course of years. It was one of the last traditions of spontaneously fermented beer left in Europe.
That’s still how lambics (and a few other Belgian beers) are made. Once they put the boiling wort in the coolship, brewers stand back and let nature take its course. What follows is a strange and wonderful dance of microbes captured by that pan of cooling wort. They each contribute different flavor and aroma compounds to the beer, and they each act at different times. Apiculate yeasts and Saccharomyces (regular, but wild, ale yeasts) are the first to act, and within a few days they add enough alcohol to make the solution somewhat sterile. Pediococcus bacteria become active after about four months, and they create lactic acid, making these beers tart. The last major actor is Brettanomyces, which will begin adding fruity esters within weeks, and then continue to ferment complex sugars for years.
Spontaneous ales are recognizable by their complexity, tartness, and funky flavors, but their differences are surprising. Brettanomyces, in particular, is an amazingly diverse yeast. Some strains produce fruity compounds (depending on the strain, they might taste like mango, cherries, or lemon). Some are decidedly funky or leathery, others softer and rounded. Even in a tiny region, such as the Payottenland of Belgium, the microbes vary from one brewery to the next. Jean Van Roy, who now runs things at Cantillon in Brussels, told me he’d seen laboratory analyses of the different lambics. “They make a picture of the Brettanomyces in each lambic. They analyzed lambic from seven, eight different breweries. All the pictures are different.”
Jason Kahler echoes Van Roy and points out that when you pitch lab-grown Brettanomyces, you’re not getting this region-by-region variability. “You’re not embracing your terroir — which I’m a big fan of. You should just embrace what you have.” Wild brewing is, unlike any other kind of beer making, a product of place, making these beers irreproducible anywhere else. They lend themselves to blending, to the use of fruit, and to slow aging. Among connoisseurs, lambics and especially gueuze (a blend of different lambic vintages) are often considered the best beers in the world. And while the brewer and blender play important roles, it all comes down to the action of those unique local microorganisms. Boon’s doesn’t taste like Cantillon’s or Girardin’s, which don’t taste like Allagash’s or Solera’s — or what you’ll produce if you use this technique at home.
There are two important elements in brewing spontaneous ales: inoculation and aging. Inoculation is variable and uncontrollable. It not only depends on the location of inoculation, but the season and ambient temperatures. In Belgium lambic is only made between November and March. There are too many microbes in the summer air, and the wort stays too warm for too long. Even within the season lambic makers watch the weather and select days when the temperature will be what they like. “The best temperature for me is around 0° Celsius [32°F],” Van Roy says. He continues, describing how cool the inoculated wort should drop overnight. “The goal is to reach between 18 and 20°C [64–68°F] tomorrow morning.”
Location matters a lot, too. Daniel Hynes, the founding brewer at Thunder Island (he then moved to Breakside), ran an experiment where he placed 1-gallon buckets of wort in Portland’s Forest Park, a 5,200-acre plot dense with Douglas firs. It was a part of the Beers Made by Walking project, in which brewers use foraged ingredients to make beer. Hynes was out to forage wild yeast. It was winter, just following an ice storm. He scattered buckets around the forest for 24 hours, leaving them in different types of locations: next to a decomposing nurse log, by an old snag full of holes, in a patch of new growth, and three other spots.
He then pitched each bucket into larger volumes of wort, inoculating them with the bugs found in the forest. Despite the fact that all the beer came from the same forest, he made a surprising discovery. The old-growth and nurse-log worts produces the sweetest, most interesting worts and were richest in microorganisms. The worst-performing wort came from the newer growth. But more important, they were all different.
Maybe this isn’t surprising. When I visited his brewery, the lambic maker Frank Boon shared his thoughts about where to find the best yeasts. “If your brewery is on the top of the hill, you will always have less wild yeast: temperatures in the night, difference of temperature in the night, and wind also. If you look at it from another side, the old English books will tell you if you’re going to build a new brewery, put it on the top of a hill and make the opening of your cellars from the north. To keep the wild bugs out. So if you put it close to the river and put the openings to the south, you will have much more wild yeasts. If you count wild yeasts in the air, you will find much more wild yeasts near a river than at the top of a hill; if you count bacteria, it’s about the same.”
Aging the beer is another critical element. Spontaneous ales take a long time to develop, so each different species of yeast and bacteria has a chance to impart its own character. The importance of time and oxygen were discussed in the previous chapter, so I won’t repeat it here, and different techniques to accomplish the aging will be discussed in Next Steps. The main thing to note is that these are slow beers, and you have to let them develop. In the recipe that follows, where you’ll be inoculating with the yeast on the skins of fruit, the aging process is only a year long. But if you try a lambic-style spontaneous ferment, you’ll notice changes up to three years later.
The final note has to do with temperament. If you wanted to boil the whole of modern brewing to a single goal, you would say that it involves trying to gain as much control over the biochemistry of the brewing process. This approach seems fundamentally contrary to brewing wild, which requires the embrace of randomness. When I visited Cantillon back in 2011, Van Roy — who is equal parts poet, philosopher, and brewer — put it this way. “It’s never the same. Never. You never know what you will discover. That’s why lambic is so fun.”
In French we have a saying, Tout est dans tout. If I translate it: everything is in everything. In this brewery, everything is playing a role in the final product. Everything.
— Jean Van Roy, Cantillon
This is not the approach of the modern brewer; it’s something closer to an alchemist, which Kahler acknowledged. “It’s kind of magical in my head. There’s obviously hard science behind it, but I don’t understand all that science, and I don’t think you have to understand that science.” He continued: “I don’t worry too much about [it]. Getting back to philosophy: you have to get over your fear if you’re going to try these beers. You can’t lose sleep over something like this.”
Remember Charlie Papazian’s old maxim? “Relax. Don’t worry. Have a homebrew.” There’s something of that approach in brewing wild. Put yourself in the right frame of mind, and just do it. The worst thing that can happen is you’ll lose a few gallons of wort. On the other hand, you may make a batch of ambrosia.
In Jason Kahler’s recipe, he calls for inoculation by fruit, an easy process that takes some of the guesswork out of natural fermentation. Discussion of spontaneous ferments follows in Next Steps.
Jason Kahler
Solera
Chill wort to 65°F (18°C) and add 10 pounds whole organic sour cherries, preferably straight from the tree or farmer. Fruit from a grocery store has been washed and handled; it’s best if you can find a source with lots of yeast on the skins. Spontaneous ferments take longer to show visible signs of activity; don’t panic if alcohol fermentation doesn’t begin for 48 hours, and don’t expect the quick, vigorous ferment of cultured yeast.
Keep in a dark place, and don’t move the carboy around. It’s best to keep it around 65°F (18°C), but this isn’t absolutely critical. Kahler mentioned an experience he had. “I actually had a woodshed outside, and it would get up to the 100s in the summer, and it would freeze in the winter. I got a couple of years out of it before it went acetic.”
Don’t start tasting the beer until 9 months have gone by, and limit the number of times you sample it; 1 year should be enough time — meaning you can do these beers annually, with the fruit harvest. After a year the microorganisms will have fully consumed the fruit and left only the pits behind.
Bottle-condition or keg.
Notes: The base beer recipe is flexible. If you want more color, substitute Vienna or Munich for a portion of the pilsner malt. Kahler’s recipes generally fall within these parameters: 80 to 90 percent pilsner malt, 5 to 10 percent white wheat malt, 5 to 10 percent Carapils. He then adds up to 10 percent acidulated malt at lautering. This recipe will give you an initial OG of 11° P/1.044. You’ll pick up the extra sugars when you add fruit, which accounts for the 13.5° P/1.055 values listed above. If you substitute other fruit for cherries, you will end up with a different gravity.
If you’re worried about not using hops, you can use up to 10 IBUs of low-alpha varieties, and if you’re using hops, boil for 1 hour. If you’re not using hops, you can also just raise the wort to 180°F (82°C) and hold for 10 minutes, a practice Kahler uses. Use any fruit you like, but those that ripen on trees will have a longer time to collect yeast. Kahler is a fan of cherries and peaches. You may want to remove the pits of some fruits, such as peaches, before adding them.
If you want to experiment with lambic-style spontaneous fermentation, both Jason Kahler and Daniel Hynes recommend starting with small amounts placed in multiple locations. They suggest that you start with a very basic recipe — just a simple wort of around 1.040 to 1.045 (10 or 11° P). Both even suggest starting with a quick batch made with dry malt extract. Many lambic makers create a dextrinous “turbid mash” to give Brettanomyces something to munch on, but for this stage of things, a simpler, easily fermented batch is fine. Start out with a regular 5-gallon batch; then divide the wort into equal portions, and place it in different locations you think might be rich in healthy yeast and bacteria (heeding Boon’s advice above).
Climates vary widely, so follow these basic guidelines for season and temperature. You want it to be cool but not frozen. Overnight temperatures under 50°F (10°C) are a must, and it’s better if the temperature is between freezing and 40°F (4°C). Hynes used sterilized plastic buckets, drilling holes in the lid to let in the microorganisms. Kahler uses open collectors protected by cheesecloth “to keep stuff from falling in there” (wise advice). The amount of liquid is so small that it will cool quickly, much more quickly than wort in Belgian coolships. As mentioned, because of the volume, Cantillon’s beer ends up in the 60s F (16–21°C) by the morning, which will be far warmer than a gallon placed in your backyard. It doesn’t seem to matter, though, so don’t worry about the shape of the collector.
Place the wort samples in the evening, as the temperatures are falling, and retrieve them in the morning, putting them in sterilized carboys. Kahler waits until after the first freeze, which he thinks might help clear the air of a lot of the “crap” that inhabits it during the warmer months. (Europeans have long eschewed brewing in the summer for exactly this reason. In Belgium they called it the “taste of summer,” which in this case was a very bad thing. One nineteenth-century source wrote, “The result strongly affected the taste and the more or less nauseating odor is the true character of this kind of ferment.”)
You’re going to have to let the samples ferment for some period of time to begin to guess what kind of bugs you found. You don’t have to wait for months, though. If any of your ferments have gone badly wrong, you’ll know in a few weeks. Let the worts go through primary fermentation, and then you can begin tasting to see if you’re getting something promising. When you have a batch you think is doing well, create a wort using the ingredient and formulation Kahler provided above and blend it with the smaller portion of wild beer. You’ll need to let that batch sit at least a year, during which time it may go through a “sick” stage when bacteria produce slimy ropes or form an unsightly fungal matting (called a pellicle). Both are totally normal, and the pellicle is actually beneficial development; it will protect the wort from oxygen.
Modified solera programs are in use in a few breweries now, but they look a bit different from the original soleras that were developed in Portugal and Spain to age wine and sherry. In that system a solera is a network of oak barrels stacked in rows that are used to slowly age the wine. After the harvest an equal portion of wine (usually 25 to 50 percent) is taken from each barrel on the bottom row for bottling and sale. The same amount is removed from the barrels in the next row up and added to the older row beneath, and on down the line like that until the barrels in the top row have space for that year’s wine. The process incorporates blending, so the finished product, though composed of many different vintages, will have a recognizable, complex flavor. In this way it’s different from aged wine, which is particular to a given year’s crop.
This process is so easy it seems like a cheat. The idea is to keep alive an ecosystem that has produced an especially tasty batch of wild ale. Kahler discovered it on his own as a way of preserving the serendipitous conditions that led to very good batches of spontaneous ales. He had been blending different batches of wild ales, leaving behind partly filled carboys. Rather than blend all the carboys out, he decided to top them off with fresh wort. “I thought, ‘I like what this one’s doing, and I’d like to have some of that in the future.’ So I kept them going like that.” Those living microorganisms fermented the wort, reproducing the original beer.
The advantages of this system are many. It’s not only a way to replicate a great batch — something that’s nearly impossible with spontaneous ferments — but it gives the avid wild-ale brewer a palette of different flavors for blending. Counterintuitively, this may mean keeping around one or two carboys that have flavors too strong or odd on their own — but that can add wonderful accents in a blend.
The first step is waiting until you have a batch you want to preserve. You can use this system with spontaneously fermented beer or with beer made by pitching wild cultures. In either case the yeast and bacteria will come into a natural harmony inside the carboy. This is the same process New Belgium uses in its expansive aging program. When I spoke to brewer Peter Bouckaert, he talked about each foeder as though it had a personality. “Foeder number two, that one we had to rebuild because it was leaky. We tried to rebuild it, and it worked, but that one produces a lot of the high acidic to lactic formations. Foeder number nine always produced lactic and ropiness.” New Belgium has so many different foeders — each making a unique beer — that they have enormous flexibility in how a finished beer tastes.
It’s good to give the first generation enough time to find this harmony; Kahler suggests a year to a year and a half. Once that generation is ready, you can pull off roughly two-thirds of the batch and top off with fresh wort. “It’s all about care and feeding,” he says. Subsequent generations are far speedier. “About three to four months later, I’ve found you have a beer that tastes like it’s a year old.”
An additional benefit of this system is that introducing fresh wort allows you to introduce oxygen into the carboy. Kahler has always maintained nonporous steel soleras, but adding fresh wort provides oxygen that would be available in staves in other aging systems. “I found no issues using stainless versus wood. When you’re adding fresh wort to a solera, oxygenate it a little bit. Part of the endgame in doing that is you’re making food; you’re trying to keep these things alive and healthy.” That’s why you do it every four months: “a feeding period.” With the solera system, you don’t have to worry about wood aging to get that oxygen.
Finally, if you want to work with fruit after you’ve got soleras going, rack off the typical amount into a separate carboy, add fruit, and top off with fresh wort. If you’re not inoculating with fruit, you don’t have to buy organic produce straight from the farmer. The native yeasts will take care of things.
