Taming the Wildflowers — The Beautiful and Distinctive House Yeasts of British Brewing

In March 2000, a shipment of the very first bottles of Imperial Extra Double Stout from Harvey’s Brewery in Sussex, England, arrived in New York. The beer had had nine months of conditioning time at the brewery before a further month in transit across the Atlantic. It was designed to be a close recreation of the original Le Coq Imperial Export Double Stout, shipped to Russia from London in the 19th century. 

When the Stout arrived in New York, the importer was ecstatic. “We are delighted at the aroma, flavor and taste profile. As we wished, so much—even some tart/sour undercurrents—can be tasted (which must have been the case 200 years ago when the components were matured in oak barrels). We certainly do not want you to change anything in the recipe! Leave everything as-is.” 

The beer was launched to much fanfare at the Russian Tea Room, but back home in Sussex a disaster was brewing. By July, a handful of bottles left in head brewer Miles Jenner’s office had corks which were slowly rising up the necks of the bottles, held back only by the foil closure, and which opened with a Champagne-like eruption. 

A second batch of the beer was put into tank shortly after the maiden brew had been bottled, and this time the brewery held it there for 12 months, finding that after nine months a sudden and violent secondary fermentation took place. At the height of that fermentation, 30lbs of carbon dioxide pressure were being released from the tanks overnight.

What the brewers discovered was that the trusty Harvey’s house yeast—which had become such an important and distinctive part of the brewery’s output—was in fact a mixture of two strains. In all of its beers aside from the Russian Stout, the second dormant strain was undetectable—even by the in-house lab. 

“It’s only under the conditions of long storage for nine-to-10 months in tank, by which time our own yeast is totally depleted, the secondary yeast strain awakens and, after a lengthy lag phase, kicks in to dramatic effect,” says Jenner.

This combination of yeasts gave the Double Stout a delicious vinous quality and deep, earthy complexity. When it first launched in New York, the Ale Street News wrote, “Massive nose and flavor—liquorice, pomegranate, currants, prunes, toffee, celery, molasses, spare ribs. What isn’t in this beer? So complex you can find almost anything.”

Harvey’s went to great lengths to find the culprit at the center of the surprise fermentation, and through DNA sequencing isolated it as Debaryomyces hansenii, a yeast strain rarely associated with beer, and first found on mushrooms in the 1920s. It’s an offspring of two strains—Brettanomyces claussenii and Pichia farinosa—so any flavor similarities with Brett are not entirely surprising.

Still, for the vast majority of Harvey’s beers—including its famed Sussex Best—the sleeping giant never gets a chance to rear its head, and it is the dominant, primary yeast that has done the work of creating beers with a distinct character for decades.

“My father used to give me a glass of beer when I was a kid in the sample room and there are times when I go down and have a glass and just think, ‘My god, that is exactly what it tasted like as a child,’” says Jenner. “There’s a strange characteristic to all of our beers which always reminds me of warm bread dough; to me that is the very heart of Harveys.”

BURNING AMBITIONS

Modern brewing really began once we were able to isolate and control yeast, like picking a rose from a meadow of wildflowers and weeds and cultivating it until it suited our needs. Today’s brewers have hundreds of strains they can order up from myriad yeast banks and labs, a vast world of microorganisms at their fingertips.

But some breweries have resisted that plenitude and ease, and have stuck with, and shepherded, their own house strains and cultures across decades. Those yeasts can originate from all kinds of sources—whether collected in nature, borrowed from other breweries, or handed down through the generations—and are used to impart flavors, textures, and characteristics which drinkers come to know as the breweries’ signatures. Harnessing and controlling that in-house yeast—cropping from prior batches and keeping the yeast healthy and fervent—is all part of the brewer’s art.

Just down the road from Harvey’s, another brewery takes its adventures in fermentation a few steps further, combining mixed cultures with the barrel-aging and blending techniques of Belgian brewers to dramatic effect.

The intricate, complex beers of Burning Sky in nearby Firle, Sussex, are considered among the best “wild” beers in the U.K. The brewery’s distinct house culture—a mix of  Saccharomyces cerevisiae, Lactobacillus, and Brettanomyces—works in combination with barrel- or foeder-aging and blending to create unique and spectacular beers, most often packaged in sturdy, Champagne-style bottles designed for cellaring.

“Our house mixed culture is a Saison strain isolated from a Belgian brewery and then also a Lacto and Brettanomyces strain, none of which are commercially available,” says founder and head brewer Mark Tranter. “I chose them as a mix at a homebrew level, before Burning Sky even existed, and now as time has marched on they’ve mutated, to become more distinct and our own.”

Tranter made his name brewing hop-forward, modern Pale Ales and Bitters at Dark Star, a then small but influential brewery based out of the Morning Star pub in Brighton, later purchased by Fuller’s and in turn Asahi. “The best part of 10 years ago, I started formulating this plan—but I knew there was no place at Dark Star for Burning Sky,” says Tranter.

What came next was the creation of an entirely different type of brewery, based out of a refurbished farm building in the South Downs and focused on beers with an admittedly niche appeal. “Mixed-fermentation beers hadn’t hit the mainstream, and I don’t think they ever will, which is why we’re quite a small brewery,” Tranter says wryly.

Across Burning Sky’s range of aged and blended beers, that mixed culture adds a cider-like tartness, while a distinctive white-pepper note from the Brettanomyces imparts complexity. The beers are not aggressively sour, but acidity is used more as a component of the overall flavor profile. All are thoughtful and considered, much like the man who brews them.

“The flavors I want [our culture] to impart in our beers are the ones which I’ve come to enjoy, the ones which I’ve developed—somewhere between wild beer, low-intervention cider, and natural wine. Something that questions what beer is and what it can be,” says Tranter.

Burning Sky’s huge oak foeders are used to age many of the brewery’s mixed-fermentation vintages. The brewers taste and blend the results to create Gueuze-like beers with balanced acidity, funk, and wood tannins. After leaving the farmhouse, Burning Sky’s mixed-fermentation beers will continue to mature and develop in the bottle for years, usually for the better.

“Around 18 months ago, I opened a bottle of Saison à la Provision from our first batch [in 2013] and, I don’t mean to blow our own trumpet, but it tasted like it had been bottled the week before—it was so fresh,” says Tranter. “It was exceptional and gave us the confidence to begin putting 10 years on our bottles.”

With the installation of the brewery’s coolship in 2017 to produce Lambic-style spontaneously fermented beers, Burning Sky has since explored further possibilities for what its beers can be, allowing the wild yeasts swirling in the farmhouse to join the party. As the beers slowly condition and evolve in their barrels, so does the brewery itself—looking forward by looking back, harnessing the techniques and traditions of brewing’s wild past.

HIP TO BE SQUARE

They say if you wait long enough, everything comes back into style.

Black Sheep Brewery in Masham, North Yorkshire brews using centuries-old Yorkshire square fermenters and a process which, while once commonplace across the region, now only survives at a handful of Yorkshire family brewers. Rather than a nostalgic nod towards the past, these fermenters are an ingenious tool, and lend a truly distinct character to the beers—particularly the brewery’s bone-dry Pale Bitters.

Black Sheep’s yeast, too, is a key part of the equation. As Paul Theakston, the brewery’s founder, notes, his team are “the current guardians of the yeast.” It has been in use since at least the 1920s, at the now-shuttered Hardy & Hanson’s Brewery in Nottingham, from which Black Sheep purchased its first square fermenters in 1992.

When speaking to Dan Scott Paul, Black Sheep’s current head brewer, I comment that I’ve always found the brewery’s beers to have a wonderful flinty dryness—they’re very clean, and never overly hoppy. How much of that character is down to the house yeast and to the Yorkshire squares, I want to know? 

“The two go hand in hand […] and I say with confidence that the crisp and dry nature of our beers is certainly due to the Yorkshire square method,” Paul tells me. “In particular the rousing process. The regular mixing of yeast and beer gives a yeast bite to our beers, which imparts this dry and crisp nature.” 

The brewing process of those Yorkshire squares is unusual. The yeast ferments the wort with vigor, causing it to rise and flow out of the two-story squares and onto a walled deck, separating the beer from the yeast. The brewers later “rouse” the beer for six minutes every three hours during fermentation, pumping the fermented wort from the bottom of the tank and spraying it over the top of the brew. 

You can taste the effects of this feverish fermentation most clearly in the brewery’s famed Best Bitter, says Paul. “Traditional Yorkshire Bitters are famed for their crisp and dry nature, no doubt due to the extensive use of Yorkshire squares in the past. Our Bitter is no different. To complement the spice and fruit the yeast provides, we use Fuggles as a late hop, which imparts a peppery aroma and finish to the beer.”

Much like traditional lagering, the brewery also employs a cold-conditioning phase after fermentation in separate conditioning tanks, which Paul says is vital to allow the flavor to develop, the yeast to drop out, and the hop bitterness to round off. “If we didn’t condition, then the dryness of the beer would be too overwhelming and ruin drinkability,” he says.

In other Black Sheep beers, such as its Riggwelter Strong Yorkshire Ale, that crisp, high attenuation combines with a grainy, sweet malt character to create a biscuit-like flavor and complex palate of licorice, banana, and light roastiness. For a big beer, it is incredibly well-balanced, and the fermentation process ensures the sweet elements never become overly cloying or heavy. 

Another side-effect of the unique brewing process is a fast fermentation and high carbonation levels, which seem at odds with the full, almost creamy beer that you can expect to find in the glass when visiting a Black Sheep pub. “The higher carbonation adds a lovely mouthfeel to all of our beers, which is especially apparent when pulled through a swan-neck [and] sparkler,” Paul says.

In the north of England, it would be sacrilege to serve Bitter through anything other than a tight sparkler—essentially a showerhead for the end of the spout, which froths the beer in the glass to create a tight, white, sturdy head of foam. While at the bar in The Maltings in York, North Yorkshire, I watch two half-pulled pints of pale copper Black Sheep Best Bitter settle, and I can smell the spice and fruit of the hops from feet away. It’s a way of serving the beer which suits Black Sheep’s classic Yorkshire-style Bitter perfectly, and is a fitting way of ending the journey of a truly unique style of beer.

PASTURES NEW

Traveling around Britain takes longer than you’d expect, thanks to our patchwork of rail routes and winding roads, but few breweries merit a long trip more than Verdant Brewing Co., located in Penryn, Cornwall, on the tip of southwestern England. The brewery’s name is apt, given the vivid fields and stretches of beach that surround it. Its beers are equally vibrant, and, yes, verdant. 

Surrounding environment, brew kit, and the brewers’ skills are the reasons that identical recipes brewed in different locations can yield vastly different results. Most breweries also keep their house yeast under lock and key, keeping it healthy behind closed doors but not sharing their secrets outside of the brewhouse.

“We were always very keen to end up with a house yeast which we could harvest and repitch—to get to know its foibles—and had done a bunch of pilot brews with London Ale Three and noticed that after a few generations it hits a certain character in our beers that we really enjoyed. So I got it analyzed at that point, genetically sequenced and stored,” says James Heffron, co-founder and head brewer at Verdant.

That character is a pronounced stonefruit softness in combination with a subtle vanilla sweetness. It has become the trademark of Verdant’s superbly aromatic and textured New England Pale Ales and IPAs. 

“The most clear combination of our yeast character at work is I would say [in one beer called] Fruit, Car, Sight, Exhibition—which just happens to be an 8% Double IPA—as you’ve got some very noticeable qualities of apricot and vanilla and then just lots and lots of Citra character, which I just think is such a good showcase for the yeast,” says Heffron.

Verdant’s house strain is now used across its range, on everything from big, bold NEIPAs to low-ABV Pale Ales, Bitters, and Stouts. Recently, I was blown away by the Citra- and Mosaic-hopped People, Money, Space, Time. That characteristic fullness, and apricot fruit hit, was front and center, adding complexity to the tropical fruit and citrus of the hops.

In the context of Verdant’s annual Export Stout, Heffron says the yeast adds a big, full mouthfeel, but it also lets the malts shine, and brings an added complexity to their rich, roasted, chocolatey character. “It works wonderfully in dark beers. It’s a yeast that loves malts. You know when I look at a dark beer I expect it to be relatively luxurious and somehow, this yeast makes that happen.”

Rather than keep their super-yeast discovery to themselves, Verdant’s brewers decided to work with yeast specialists Lallemand to isolate and reproduce their house strain for public sale. “We never viewed the sharing of knowledge as secrets being stolen and from very, very early on, we weren’t really interested in some sort of this shroud of mystery,” says Heffron. “It’s about trying to elevate the whole industry, not trying to be selfish-minded in any way.” 

Verdant is a unique brewery with a refreshing outlook, which has translated into an output of world-class beers. At the center of the brewery’s work is a yeast which is truly its own, and yet is also now all of ours. 

“You know, to be able to go from what was an idea on a kitchen stove, to starting a brewery, to then have the yeast being available to anyone that wants it all around the world—whether that’s commercially or on a homebrew scale—I think I just I find that endlessly fascinating and exciting,” Heffron says.

Words by Neil Walker
Illustrations by Colette Holston