Editor's note: This story about White Labs appeared in The
San Diego Union-Tribune on Jan. 21, 2000. Peter Rowe, the author,
writes a monthly feature for the newspaper called "Brewery Rowe."
Yeast is beer's unsung hero
By Peter Rowe
The San Diego Union-Tribune
You know what they say about beer's ingredients. "It's the water."
"The finest hops."
"The choicest barley malt."
You know what they don't say. "It' s the single-celled fungi."
In the kingdom of beer, yeast is Cinderella before the ball. After slaving away,
the homely little ingredient is expected to fade into the wallpaper -- easy to do
when you' re microscopic -- and let the glamour pusses take the bows.
"Sometimes yeast doesn't even get mentioned," said Chris White, a professor
of biochemistry at UCSD and the proprietor of White Labs in Mira Mesa.
"All you hear about is malt, water, hops."
Yeast, though, plays a crucial role -- some say the crucial role -- in brewing.
These microscopic characters are the stars of a fabulous yarn, which zig-zags
from medieval European monasteries to a 19th century Parisian laboratory. A
truly romantic saga, it' s all about chemistry.
Let' s start with a shamelessly sketchy explanation of brewing. Malted barley
and hops are boiled in a large kettle, cooled, then drained into a fermentation
vessel. Here, yeast is added, or "pitched." The fluid is thick with sugars, which
the yeast feasts upon, producing alcohol and carbon dioxide in the finished
For centuries, this chemical process was a mystery. Beer drinkers owe a lot
to Europe' s monks -- hops were first cultivated by Christian brothers in the
eighth century, and monastic orders devised one classic beer style after
another -- but even they were baffled by yeast. They understood, though, that
when fermenting liquids were briefly exposed to the heavens, something
"God is good," the monks pronounced.
What was happening? "Yeast is in the air," explained White. In the air and on
every surface. At this moment, thousands of yeast cells are thriving on your
skin. "There' s more in your gut," he added.
Those wild yeasts are unsuited for brewing, though, even if you were
concocting a batch of, say, Peeling Skin Pilsner. Brewers' yeast evolved from
the work of Louis Pasteur, the French scientist who, in 1866, peered through
a microscope and saw that yeast caused fermentation. Fifteen years later,
Emil Jansen, a chemist with the Danish brewery Carlsberg, discovered that
yeast came in various species.
Today, two main species are used in brewing. Saccharomyces Cerevisiae is
employed primarily in ales, and Saccharomyces Uvarum in lagers. Each offers
brewers countless strains.
"Only certain types of strains will make good beer," White warned.
And each strain has its own character. Brewers look at a yeast' s
"attenuation," or how efficiently it consumes sugars, and its "flocculation," or
how quickly it drops from suspension.
Beermakers also consider the more than 600 flavor and aroma compounds
that issue from yeasts. A California ale yeast, for instance, is almost tasteless,
allowing the natural properties of hops and malts to shine. An English yeast,
though, adds apple-and plum-like textures. Because it is less attenuating than
the California strain, the English produces a sweeter beer.
The exact yeast used in a specific beer is often a trade secret. White Labs,
which provides yeast to 700 American commercial breweries and more than
1,100 home-brew shops, guards its customers' orders.
"Our relationship with a brewery is kind of like your relationship with your
priest or doctor," said Chris Mueller, White's vice president.
In fact, yeast is treated like a burn patient. When you care for either, what's
the overriding concern? "Three words: sanitation, sanitation, sanitation," said
Marty Johnson, brewing manager for Karl Strauss Brewery.
"That's the whole ballgame. You've got to create a pure yeast strain."
Mueller agreed. "Yeast is really easy to grow. Pure yeast -- single-strain yeast
-- is extremely hard and very technical."
Mueller calls his firm "a biotech company," and touring White Lab's
warehouses, you see what he means. There are cryogenic vaults, where yeast
is stored at minus-80 degrees Celsius. There' s an autoclave, a large pressure
cooker that sterilizes beakers and other containers at temperatures of 250
White started this company in 1993, selling yeast to the Home Brew Mart
while he completed work on a Ph.D in biochemistry at UCSD. In 1997, he
met Mueller, then a marketer for Genentech. They clicked; sales soared.
"In one month," Mueller said, "we tripled our business."
In the mid-1990s, White served roughly 1 percent of U.S. brewers. Now, the
figure is around 50 percent. The clientele includes most of San Diego County's microbreweries; the Rock Bottom chain; California upstarts such as Russian
River, Anderson Valley, Sudwerk and Twenty Tank; Colorado' s Wynkoop;
Montana' s Spanish Peaks; Old Dominion in Virginia, Dock Street in
Pennsylvania, Frederick in Maryland and many more.
Locally, Karl Strauss is an exception to this rule, sticking with the German
yeast that launched the minichain 11 years ago.
"Our yeast gives a very fruity, sweet finish to our beers," Johnson said.
To illustrate yeast's versatility, the brewing program at Oregon State
University shipped to White Labs a dozen batches of beer made from a single
recipe. The only ingredient that varied, from batch to batch, was the yeast
White, Mueller and I sampled the brews, finding an astounding range of
flavors. The Irish yeast made for a fruity, yet dry, beer. Burton yeast
produced a sharper beer, with hints of pear and clover honey. East Coast
yeast reminded us of bread. Kolsch yeast, of sulfur.
As we sipped, Mueller told tales. At a beer conference, one story goes, a
ferocious argument rocked the meeting hall. The question: who was the
Finally, one man brought the debate to a close.
"The greatest brewer?" he shouted. "It' s the yeast. You guys are just the