A happy yeast is a productive yeast


The fermentation process is where the yeast does the heavy lifting.

By Jim Witmer

If brewing yeast could talk, you might hear them saying, “We have to do all the work around here.”

Yeast strains involved in the brewing process have the critical task of turning sugars into flavor, alcohol, and, ultimately, the beer we all love. Without yeast doing its thing, beer would just be a hoppy, sugary solution devoid of anything truly enjoyable.

Despite all the work they do, they seem to have the most fun in the brewhouse—short-lived as it might be—as they wake up and go to work. This microscopic scenario has been likened to a delirious frat party. As soon as a brewer can create the sugary liquid from the malted grains and cool it down to a temperature that yeast like the best, they start feasting and gorging, copulating and multiplying, all the while expelling gas
and alcohol.

Eventually, these single-celled organisms are doomed by their intense partying. Making alcohol is what will eventually kill them, or at least make them go dormant. Depending on the strain of yeast, the range of alcohol produced by beer yeast can be from 4.5 percent to 18 percent, and in most cases the toxicity can’t be tolerated. Brewers come to the rescue and pull them out of the toxic environment they created and nurse the survivors back to good health so that they can get back to having more fun in another batch of brew.

Beer yeast (Saccharomyces) has the responsibility of defining the two main families of beer styles—lagers and ales. Ales ferment best in warm temps and lagers in cooler temps. But while hops get all the glory these days, yeast has the potential to create the most unique and delicious flavors possible, as long as things go as planned. But if the yeast is unhappy with some of the conditions, such as temperature or the workload (too much sugar to eat), it becomes stressed out and will throw off unpalatable flavors and aromas. They often have a chronic sense of entitlement, and that’s why good brewers like to keep them happy.

When beer yeast is happiest and in a warm environment, subtle flavors and aromas that the yeast impart from fermentation (called esters) are banana, pear, apple, clove, and honey, and you’ll find them in ales originating in the European continent. By contrast, American ale yeast is “cleaner,” which lets the hops take center stage, quite by design. Lager strains, on the other hand, produce even less esters and are loved by many drinkers across the globe for their crisp, clean, dry character, and the exquisite lack of overwhelming flavors.

Every style of beer is the result of yeast defining what character it will bestow and ultimately its classification. Take a German hefeweizen (wheat) for example. Because Germans do not fool around with adding other ingredients besides yeast, water, hops, and grains, how else would it be possible to get the distinct character of banana, clove, bubblegum, and apples in a beer? It’s all about the yeast strain interacting with the wheat during metabolism in a complicated biotransformation, but the production of this beer celebrates the inherent yeast by leaving it in suspension. German wheat beers aren’t suitable for everyone’s palate, and can have a strange and quirky essence to those who are unfamiliar. These flavors, known as phenolics, are representative of various genres. If you like German Wheat beers, you probably also like Belgian beers.

Belgian beers have a unique, unmistakable character that is solely derived from the yeast. It’s the spicy clove, peppery, archetypical liquid that some people love, but others might loathe. While Belgian brewers are often found supplementing their beers with fruit and spices, their yeasts are already fruity by nature.

But to further push the boundaries of yeast, sour and tart beers are the paradoxical members of the family. The peculiar character that these uncultivated ales bring to the table has turned the U.S. craft beer world on its head. Brett (Brettanomyces) is the principal wild yeast used in sour beer production. The range of flavors, aromas, esters, and phenols ranging from tropical fruit to horse blanket that make this style compelling, typically take a much longer time to complete the job, but in turn can be
highly rewarding.

The famous British beer writer Michael Jackson described the behavior of lager and ale yeast in a brewery as a figurative pet dog—well behaved and reliable—but the yeasts used in sour beer are like a wild cat—unpredictable and might scratch you if
handled improperly.

Until the invention of the microscope in the early 1700s, yeast’s important role in the fermentation phase of brewing was not even considered. Brewing folklore speaks of magic brewing sticks that were passed through generations that actually contained the bewitchment of microscopic cells we know as yeast. Of course, today there are hundreds and hundreds of different types engineered and cultured. In many cases, they are a mega-brewery’s highest proprietary holdings and involve pentagon-like security measures to protect their esoteric value.

So the next time you are fortunate enough to pour a glass from a bottle of conditioned beer, take note of the yeast layer clinging loosely in the bottom, then swirl it around and add it to the top of the head for even more flavor and a dash of B vitamins, protein, and minerals, and be reminded that they worked hard for your gratification.

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Reach DCP beer writer Jim Witmer at JimWitmer@DaytonCityPaper.com

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