When considering the flavors in craft beer, it’s easy to be enamored by the hops. Hops are hyped, worshipped, and are even included in the names and label designs of many craft beers. But there’s another ingredient that you should pay attention to: yeast.
Without yeast, there would be no beer (or alcohol, for that matter). During the fermentation process, the microorganism eats sugar and creates alcohols and carbon dioxide as a by product. It’s a required ingredient just like sugar is a required ingredient. It’s also, however, an ingredient that affects flavor — just as much, if not more so, than hops.
VinePair caught up with Jason Oliver, the brewmaster at Devils Backbone in Virginia, to understand why you should care about your beer’s yeast as much as you care about your beer’s hops.
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Yeast adds fruit flavors to your beer
“Without the yeast contribution, beer would be very boring and one dimensional,” Oliver says. The fruit flavors from esters are just one dimension you’d probably miss without yeast.
Unless fruit is actually added to beer during the brewing process (which seems to be happening more and more these days), fruit notes come from a reaction between acid and alcohol. The reaction produces a chemical compound called an ester. Ale yeast, called Saccharomyces cerevisiae, is different from lager yeast, called Saccharomyces pastorianus. In terms of flavor, ale yeasts generally produce stronger fruit notes.
“A mild fruity ester might have hints of apple or pear, like in a lager, which is just barely perceivable compared to big esters that smell like banana or bubble gum that you’d find in a Belgian or hefeweizen,” Oliver says.
Strong banana flavors from Belgian yeast strains define Belgian-style beers. A yeast’s fruit notes can guide a brewer on the final tastes that will be highlighted in a beer in other styles as well, though. Oliver used a yeast strain for a lager that smelled like apple and pear, so he developed the entire beer around the esters from the yeast. The resulting Pear Lager is a crisp and evenly balanced fruity session beer.
One strain of yeast can provide an array of different flavors
The strain of yeast matters when it comes to flavor (there are literally hundreds of strains of ale yeast), but the way the yeast is treated matters as well. After all, there are more variables with yeast than there are with malt and hops, Oliver tells me. The same strain will produce different characteristics as you change the strength of the beer, the temperature while brewing, and the amount of sugar.
“Each strain behaves differently,” Oliver says. Devils Backbone, an AB InBev owned brewery, has access to a wide array of commercial yeasts, but “even in the best of times, yeast can throw you a curveball,” Oliver says. “What you try to do with fermentation is create an environment that is beneficial for yeast to grow and ferment and produce the flavors that you desire.”
Yeast’s genetic variety is underappreciated
Saccharomyces cells are incredible microorganisms. The genus name, which comes from Greek, translates into “sugar fungus.” They exists naturally all over the world, and each one creates sometimes subtle, sometimes drastic differences when fermenting sugar into alcohol.
Today, brewers are presented with an overwhelming number of yeast options. You can find a partial list broken down by style on the Brew magazine website, which lists strains like American Ale 1056, which, according to Brew is “well balanced. Ferments dry, finishes soft.” There are also strains like the Fermentis US-05, which is “clean with mild flavor for a wide range of styles.”
There are also more radical methods of obtaining yeast. At Urban Artifact in Cincinnati, Ohio, the brewers went out and collected wild yeast from a nearby monastery. They set up yeast traps, narrowed down the samples to a single strain, and brewed a Belgian-style quad called St. Anthony’s Quad. It tasted, of course, wildly yeasty.
Yeast has a long and cherished history
Brewers didn’t always have options that brewers have today. Yeast wasn’t fully understood until the early heyday of microbiology in the 19th century. Prior to that, brewers simply knew that something was making their sweet liquid turn into delicious beer. They called it, according to a Middle English dictionary at the University of Michigan, “goddes god,” or “God’s gift.”
Yeast is deemed important enough to be one of the four ingredients included in the 500-year-old Reinheitsgebot, or German Purity Law, (as soon as yeast was discovered, at least). Pilsner Urquell, the famous pilsner that defined a style, has used the same yeast strain for 173 years. It’s called the H-strain. Selling yeast was how a young Anheuser-Busch stayed open during the dry days of Prohibition.
Today, hops get most of the credit. But look to history and look to science, because you should care about your beer’s yeasts just as much as you care about your beer’s hops.