| It's All ABout The Yeast!
by Liv Hanley
The most important ingredient in brewing was the last one discovered, because yeast is a single-celled organism
that is invisible to the naked eye. Still, brewers have long known that some unseen agent turned a sweet liquid
into beer. Long ago, the action of yeast was such a blessing, yet so mysterious, that English brewers called it
Modern brewers usually brew with purified strains of yeast that give exactly the result they want. Some yeast
strains are fairly neutral, creating alcohol and little more. Others add a whole range of complex side flavors that
make beer more interesting.
How does yeast work? When it is added to a sugar-rich solution, it immediately begins to consume the sugars and
create more yeast. But from the brewer’s point of view, the important thing is not the growth of more yeast, but the
waste products of yeast metabolism: alcohol and carbon dioxide, that gives beer its fizz.
As the food supply runs down and the alcohol levels rise, the environment becomes literally toxic to the yeast,
which becomes dormant. The brewer may draw off some of the yeast for the next cycle of brewing.
With the majority of beer’s flavor and style created by yeast, it’s no stretch to say that yeast is a large part of
what puts the “craft” in craft brewing. What’s exciting for craft brewers is that the emerging revolution in brewer’s
yeast means even more intriguing variations in craft beer styles and flavors, as well as improved quality control
and consistency, are shortly on the way. With more breweries operating in the United States now than at any time
in its history, and amid an ever-increasing consumer appetite for diversity in craft beers, the industry is about to
get a helping hand from the oldest and most traditional of ingredients. A new golden age of yeast is upon us.
Yeast has unwittingly been used by people for millennia as an essential ingredient in foods and beverages such
as bread, wine, beer and cider. However, up until now we’ve been realizing only a fraction of yeast’s intrinsic
potential. In fact, it’s only in the last 150 years that we have even begun to understand yeast’s valuable
biodiversity — although this hasn’t always been capitalized on, as evidenced by the fact that only a handful of
commercial yeast strains are responsible for the vast majority of the beer produced globally.
During that time, these dominant strains have been gradually selected for easy-to-quantify and industrially
advantageous traits: temperature tolerance, neutral flavor profiles, attenuation and flocculation and ultimately the
ability to consistently produce and deliver large quantities of beer. Unfortunately, this has often been at the
expense of diversity.
Given yeast’s long-established position in the beverage industries, it’s easy to take this microbe for granted and
assume it’s a simplistic ingredient. In fact, the opposite is true. The impact yeast has is truly transformative — just
think about the difference between wort and beer. It is ultimately yeast that is responsible for turning hopped wort
into beer with all the power and subtlety, boldness and nuance we know it can have.
However, with yeast traditionally being pigeonholed as a workhorse ingredient — applied principally in large,
commodity-type applications such as baking and brewing — it’s hardly surprising that less than 1 percent of
commercially viable yeast strains are currently in production. While this might be desirable from an industrial
efficiency viewpoint, it does limit the variety of the end products that can be developed and produced
commercially at any scale.
That needn’t be the case. What we’ve failed to capitalize on fully to date is the enormous range of natural
biodiversity and interesting traits inherent in the wider yeast population. Similar to barley or hop breeding
programs, recent improvements in yeast technology — particularly in the areas of classical breeding and directed
evolution, in which natural diversity can be utilized to unlock and optimize traits of interest — have led to some
truly remarkable advances in commercial strain development.
Correcting a desirable but otherwise malfunctioning trait through adaptive evolution is one such technical
advance. Another involves introducing a new trait into an existing strain through breeding, all the while
maintaining the background strain’s functional performance and strengths. In fact, these classical techniques are
now a preferred method of choice when it comes to complex or multiple traits (such as flavor and aroma).
Advances in this area are being used to generate strains that brew as normal or, better yet, produce enhanced
flavor and aroma profiles.
So, with all of the opportunity offered by applying new technology to classical yeast biology, what is the future of
brewer’s yeast? The answer: better, exciting new functionality and traits. Given the ongoing need of craft
breweries to address consumers’ insatiable desire for new flavors, the advances in strain development should be
welcome news to brewmasters and their customers. Indeed, the future can look forward to yeast not only as it is
now, but also how it could be: delivering on its promise to open up a world of new tastes for the global craft
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