As Duration’s ‘Log Beer’ lights up Beer Twitter, Lily Waite takes a look at the enduring appeal of fermenting on weird… stuff


If my friend and colleague Matthew Curtis is to be believed, Log Beer is the next big thing of 2021. Every year has its trends, from the short-lived Brut IPA that swept fridges and shelves in 2018, to the hard seltzer that tried (and failed) to gain a foothold in the UK in 2019. As last year’s trend was, apparently, the Covid-19 pandemic all but closing everything we hold dear, 2021 swung around with great enthusiasm, and many (myself included) looked to see what this year might bring. I, for one, did not anticipate the coming of Log Beer.

I jest, of course, above—before you all rush to harangue your local beer retailers (from a safe distance) demanding to know when the next Log Beer drop might be. The good-humoured furore that took place on #BeerTwitter over Norfolk’s Duration Brewing throwing logs straight into their coolship only lasted a day or two, and it certainly looks to be a one-off, as opposed to a shift in modus operandi. That said, it got me thinking about log beer, branch beer, innumerable other ‘wild’ beers. Brewers the world over use innovative and creative methods to inoculate and add flavour and character to their beer. So, why not logs?

Logging on

Derek Bates, Duration’s co-founder and head brewer, didn’t use the oak logs—cut from the dropped limb of an oak near the brewery—to primarily introduce wild yeast or bacteria. Instead, he wanted to introduce flavour and character to the rustic saison, brewed in collaboration with Verdant Brew Co. “A week or so after open fermenting with whatever we may have picked up in the [cool]ship,” he says, “as well as the wood and our mixed culture, I can safely say it has a very definitive oak aroma and flavour. After many weeks of fermentation I’m sure this will die down, but should still leave that characteristic of oak aroma, tannins, colour, and vanilla notes.”

Though the inoculation of wort was not Bates’ primary aim, the microbiome of this rustic saison might well have been influenced by the addition of the logs. “It takes about 8-10 hours for that wort to cool down to about 20-25ºC,” he says, “so while it’s sitting in that window of, say, below 35-40ºC it could possibly still inoculate, or if it’s a wild spore-forming yeast it very much could still have something knocking about.”

Much of the wild microflora found on the logs would, unfortunately, have been killed by the heat of the wort, which was transferred into the coolship at around 100º. Generally speaking, anything housing yeast or bacteria would be introduced at much cooler temperatures, so as to avoid killing off the helpful ‘bugs’.

Bates' logs hark back to brewing practises hundreds of years old

Despite this, Bates’ logs hark back to brewing practises hundreds of years old: before brewing science and microbiology were understood in even the most rudimentary senses, tradition and, to some extent, superstition were the norm. In medieval times, wort would be inoculated by stirring the mash with a stick laden with yeast, unbeknownst to the brewer—the discovery of the presence of yeast, and the process of the subsequent fermentation wouldn’t be discovered for hundreds of years. These sticks were often passed down the generations, and are not-that-distantly related to a practice still alive today: that of the Kveik ring, a tessellating ring of wooden shapes, whose nooks and crannies harbour the much-hyped Norwegian farmhouse yeast very much traditional in northern Norway, and increasing in popularity around the world.

The most common way of inoculating freshly-brewed wort is via a coolship. Hot wort is pumped into the shallow metal vessel (most commonly stainless steel, though historically often copper) and left to cool overnight. The windows in the building are left open to encourage in airborne wild yeast and bacteria, which settle on the cooling wort. A short while later, fermentation will begin as the microflora get to work. 

Bug hunting

A common alternative, for those without coolships, or who are interested in wild yeasts further afield, is to collect yeast samples and grow them up, before pitching them as you might any other yeast. Urban Artifact Brewing is a sour-only brewery based in Cincinnati, Ohio, who harvest wild yeasts from all around them, with which to ferment spontaneous beers.

“The majority of our production is what people often deem ‘quick sours’, where we sour, prior to boiling, in stainless fermenters with our house lactobacillus,” says Chief of Brewing Operations Bret Kollman Baker. “We also have a spontaneous program where we use only local microflora and that process has been evolving the more we learn.”

Kollman Baker and team would leave hot wort in mason jars covered with cheesecloth across the brewery site and in the surrounding neighbourhood. In the morning, these would be sealed and returned to the brewery to be fermented. “Good spontaneous ferments were kept and propagated,” he says. “An exceptional sample was captured in the bell tower of the old church our taproom inhabits. We isolated the lactobacillus from this sample and use it for all our quick sours to this day.”

Though Urban Artifact harvest yeast less this way than in the past—these locally collected cultures have been developed into “a unique and slightly changing spontaneously-derived house culture”—the team still venture out when needed. “We mostly do it now if we are feeling that we need to reintroduce fresh spontaneous cultures or if there are some fun collaboration opportunities where we can go somewhere fun or exotic.” 

“We’ve gone on top of local buildings in the city,” Kollman Baker continues, “a local monastery (with real Friars and an actual saint’s relic), local cemeteries, and some long lost and rediscovered beer tunnels.” The most interesting, perhaps, were the old lagering tunnels discovered underneath Cincinnati, complete with long-disused lagering tanks, from which a brewer’s yeast sample was identified.

Two shakes of a lamb's leg

It’s not just brewers who find their yeasts in less-than-usual places. Makers of real, artisanal, craft, or dry—as it’s perhaps most often known—cider commonly don’t pitch yeast or bacteria into their juice, instead preferring to let the wild yeasts present on the skin of the fruit work their magic. Some makers do pitch—a bright, dry cider fermented with champagne yeast springs to mind. A handful of others, however, think much further outside of the proverbial box.

“I’ve fermented cider with a lacto-fermented leg of lamb,” says Nat West, president and cidermaker of Rev Nat’s Hard Cider in Portland, Oregon. “I’ve made mouth-chewed corn chicha with natural fermentation, I harvested some pumice stone that came from [local volcano] Mount Saint Helens and used that to inoculate, and I’ve used spring water from the Matsuo Shrine in Kyoto, Japan, to kick off a ferment.”

West, who describes himself as a “single-minded cider evangelist and die-hard craft beer revolutionary”, is, as evidenced above, not always drawn to the most basic of yeast sources. “The lamb cider was called Angel of Death,” he tells me. “I lacto-fermented the lamb leg, to make preserved meat/charcuterie, and starting the process by rubbing some ‘artisan’ salamis all over the raw leg. Once it had a lovely multi-colored rind, I dropped the leg into a fermenter of fresh juice. It fermented, the meat ‘cooked’ in the acid like ceviche, and fell off the bone. I waited a few months, strained it, and drank it.” The result was a bloody-tasting cider with iron deposits in the bottom of the bottles. “I did it, so no one else ever has to do it again.”

I lacto-fermented the lamb leg, and dropped it into a fermenter of fresh juice...

A cider of West’s that is a little closer to traditional wild fermenting was one in collaboration with the Portland Art Museum. 18 craft brewers from Oregon were each given an artwork to use as inspiration for a beer (or, in West’s case, cider). Assigned a still life by Childe Hassam, all West had to do was make a cider from the fruits in the painting: grapes, plums, pears, Asian pears, and apples. “But I wanted to do more,” he says.

With the help of one of the museum’s curators, West tracked down the house in which the piece was painted, and had the idea to ferment the cider using wild yeast from that garden. “I clipped off a few large boughs from this tree, including branches, twigs and leaves,” he says. “This was midsummer so everything was in full leaf. I took the tree bits back to the cidery, dropped them in a large hop bag, and lowered them into a fermenter full of juice.” A few months later, West back-sweetened with juice from the same fruit mix, and served it at the museum’s event. “It was delicious. I think I got about as close as possible to literally drinking that painting.”

Jumping the shark

Nat West isn’t the only maker who’s fermented with volcano-sourced yeast. Steve Haumschild, CEO and Brewmaster of Hawaii’s Lanikai Brewing Company, is one name that came up a lot during my research into obscure yeast sources, along with mentions of volcanoes, sharks, and, astonishingly, NASA.

Due to Hawaii’s delicate and unique ecology, importing ‘wild’ yeast—is a yeast still wild if it’s able to be imported?—is illegal. Haumschild and the team at Lanikai “aim to make Hawaii beer, not just brew beer in Hawaii,” he says. “The difference in what we do is how we go about sourcing ingredients: ultimately every single beer we have uses some Hawaii agriculture.” A lover of wild beers, and faced with no way to source packaged wild yeast, Haumschild looked to the islands.

“As a professionally trained scientist and former lab instructor for a university,” he says, “I used science to bio-prospect. Since many of our beers already reflect Hawaii’s terroir and seasonality of growing seasons, adding native yeasts would certainly add a layer in. Plus, I love exploring our islands, so I just kinda combined both of these loves.” Haumschild, like a handful of brewers in the UK, developed a mobile coolship that fit in the back of a pickup truck. With wort brewed at friends’ breweries on board, he’d drive to a location and let the wort pick up local microflora. To visit small offshore islands, he’ll use smaller, bucket-sized devices.

“It took a little over 3 years to develop our technique before we started to see some amazing results,” he says. “The locations are really opportunity-based and honestly about curiosity. They do not all work out, but there is microflora everywhere.” And, seemingly, Haumschild does look everywhere. 

He’s collected microflora from a volcano, near the centre of which is an off-grid cabin of his. After meeting NASA directors and pilots over a few beers, he partnered with the space agency to bio-prospect in the stratosphere: on a regularly-scheduled research flight a pilot opened a petri dish at 70,000 feet. Back on Earth, Haumschild grew the sample up, and set it to work. “It had a funk that initially smelled like sourdough starter,” he says, “then changed after fermentation to a beautiful balanced funk.” Not content with active volcanoes or space, Haumschild and team also bio-prospected from the backs of sharks. On a research island, and with permission from the University of Hawaii, “we would chum the water to bring sharks to our floating platform, and gently grab their dorsal and pectoral fins and swipe them.”

But, crucially, does it matter from where the yeast is sourced? Will you or I be able to taste the difference between beer fermented with microbes from a church tower in Cincinnati, or from the back of a rare shark swimming off the shore of a Hawaiian island? The answer is yes, and no.

“Honestly, each of the strains are so different that the flavours are impossible to describe,” says Haumschild. “We are brewers, so if the flavours are not there and the beer is not beautiful, we don’t make it for novelty.” The novelty and marketing potential for such beers—Haumschild describes Lanikai’s Interplanetary Ale as an “Unidentified Fermenting Object”—is inevitably huge, and would offer a pull to both beer nerds and, well, regular nerds (like myself) alike. “It must add to the beauty of the product,” Haumschild insists, “not just for marketing purposes.”

Bates takes a more characteristically sceptical approach, however. “Yeast is yeast; it could be from anywhere,” he says. “You don’t have to use a bee, or flower, or volcano—you can literally leave some Agar plates sitting out around random places and possibly catch the same yeast. There may be a case that a certain yeast is more ‘prevalent’ in areas but that’s only because it’s the same thing cycling around and around the place.”

Fortunately, this pragmatism won’t stop him from endeavours such as my beloved log beer, nor will other intrepid brewers cease their intriguing and sometimes bizarre explorations. “Too many people want to stick to the safe sells, and in particular in this climate they ain’t gonna rock the boat much for what they think will sell quickly,” Bates says. “Luckily I ain’t one of those people. If it weren’t for people taking chances and giving things a whirl, we wouldn’t be eating oysters.”

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