The Secret Life of Beer Yeast

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The world’s first organic yeast factory is right here in Gresham


Yeast is the moving part of brewing, the living factory that churns sugar into alcohol, fizz, and flavor. It’s the only ingredient that’s absolutely non-negotiable.

Originally, yeast probably came from grapes or dates added to the wort (the grain-sweetened liquid precursor to beer), while sugars might have come from millet or wheat, and flavor from saffron or grains of paradise. But beginning in the Elizabethan era, as brewing became a professional rather than domestic pursuit, beer yeast itself became domesticated, as it was selected, harvested, and passed from batch to batch over generations. Nowadays, most homebrewers know yeast as a package of refrigerated slurry that makes all the magic happen. But other than the homebrew supply store, where does beer yeast come from?

The answer, until recently, was hidden behind closed doors, because commercial yeast labs zealously guard their processes. Then along came a new commercial yeast business that has blown up some industry orthodoxy, including allowing tours of their certified organic lab.

Imperial Yeast doesn’t look like the sort of place where anything “organic” might originate. It’s located in a nondescript industrial park next to I-84. There’s no deep topsoil or sunburns involved, no banjo music or overalls. The technicians wear hairnets and lab aprons as they methodically move beakers and flasks and hoses and plastic containers full of yeast slurry around. They seem to prefer electronica to bluegrass.

Jason Stepper is the technical mind behind this gleaming, sterile microorganism farm. As he leads me from the front reception area to the lab, he gives me a hairnet and a series of instructions: You’re entering a laboratory environment; don’t touch anything unless you’re invited to do so.

As the doors to the lab open, the hum of machinery rises, and Stepper begins a swift and efficient briefing on the yeast-growing process. “So this is a laminar flow head here … that’s giving us a space to work on for initial isolation,” and there are slants and supernatant and streak plates and on and on. But by and by, it comes together.

The initial yeast strains — the mother cultures — are all kept in a minus-80 Celsius freezer, frozen in genetic time. Once a year or so, Imperial takes a tiny sample of each strain to work from and keeps them in little vials half filled with agar gel. From these, they take a minuscule scrape of yeast — a seed — to grow into enormous batches of yeast slurry. So, in that sense, it is like farming.

It’s a gradual process. The samples are first grown up in the lab. “Our day-to-day culture starts here,” Stepper explains, “then it goes into a tube, tube goes into a flask. So it has to be stepped up, incrementally.”

Then, the flasks go into gleaming stainless-steel tanks on the main production floor, which is basically a high-tech brewery. “This is a one barrel,” he says, pointing to a 31-gallon tank. He then points to increasingly massive tanks: “two barrels, four, ten, and twenties.” Clear hoses from the tanks burble violently into water-filled buckets. It looks like the “blow-off” setup a homebrewer might use to allow carbon dioxide and foam from the rapidly fizzing wort to escape. I assume that’s what’s happening here.

But here, brewing beer and growing yeast part ways. Yeast can metabolize sugars both aerobically and anaerobically (which is fermentation), but it vastly prefers the former, as it produces far more energy. So to grow the maximum number of yeast cells, to make them reproduce and keep them healthy and vigorous, the yeast farm aerates the nutritional “medium” with a steady flow of pure oxygen, which bubbles out through the tubes.

Again, though, the yeast-growing process ends like brewing. When the nutrient solution has reached “terminal gravity”— closer to the density of pure water than sugar water — the process is complete. They harvest the yeast into plastic containers, pour off the “supernatant” — which is essentially beer — and add sterile water.

What makes this process “organic” is, unfortunately, mostly proprietary information. The growth medium — what brewers call wort — is made of organically grown cane sugar and malt powder and a nutrient blend. The nutrient blend represents the year Stepper spent working at the lab bench trying to grow yeast that is sufficiently vital and vigorous, without using substances obtained through artificial synthesis.

“There’s been organic malt on the market for a while,” says Stepper. “There’s been organic hops on the market for a while. There was no organic yeast option. So if we could, it felt like we should.”

That “if we could, we should” approach is echoed by cofounder Owen Lingley, who handles the business and marketing side of Imperial. But, sitting in his office, with a conference table surrounded by whiteboards and a mini-fridge full of beer in the corner, he’s reluctant to go much into the “organic” angle of the business.

“We’re fighting that perceived stereotype,” he says. “People say, ‘Oh, it’s organic, it’s expensive.’”

But because yeast farming is an inherently expensive business, the organic certification and additional costs don’t really subtract much from the overall bottom line. In fact, Lingley says, “By cell, we’re the cheapest lab in the country. Nobody touches us. We’re the cheapest liquid lab.” To his point: 80 percent of Imperial’s business is to the commercial industry, and of that, only about five percent are organic breweries.

Instead, Imperial focuses on “pitch rate” — the amount of yeast needed to optimally ferment a batch of wort into beer. To the homebrewer, Imperial sells handsome (and recyclable) cans of yeast that contain 200 billion cells each, which they figure is optimal for five gallons of beer.

Commercial brewers, meanwhile, do what they’ve been doing for centuries: harvest and “re-pitch” their yeast into successive batches of wort. After several generations, the yeast will eventually be deemed to have “drifted” from its original genetic makeup, and they’ll order a fresh batch from the lab.

Lingley says that in his previous job as a representative for a competitor lab, he regularly came across the complaint among brewers that their beer tasted best by the second or third generation of an order of yeast. What was going on, he realized, was that they weren’t pitching enough yeast in the first batch, which was affecting the quality of the beer.

Whereas life at the yeast farm is idyllic, yeast cells go to work at the brewery, and this is hard work. Like sprinting faster than you can breathe, fermentation doesn’t leave the cell with enough energy to reproduce while being slowly poisoned by its own waste: alcohol and carbon dioxide. If each cell has too much to do, the stressed yeast starts producing undesirable flavors. In the worst case, they just give up altogether. So, great beer starts with enough cells to get the job done, without overworking them.

Does it work, or is this just marketing fluff of another stripe?

One of Imperial’s commercial customers, a big, friendly Scot named Alex McGaw, invited me down to his taproom, Two Kilts Brewing Co. in Sherwood. Over a pint of clean and malty Scottish ale, McGaw says he came to Imperial by way of Stepper, a regular customer at the taproom. Changing yeast providers is extremely risky for a brewery, so when Imperial started up, Stepper offered a complimentary pitch of Scottish ale yeast — what they call A31 Tartan — to entice McGaw to switch.

Within two years, McGaw had won his first two major beer awards for this very Scottish ale. It’s not even organic.

Mike Allen has been slowly retiring from professional cooking and butchery for years. He can be found at the crossroads of food, craft, and the environment, and at

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