All about yeast

All about yeast

By BBBC Quality Manager Jackie Beard

The past three weeks, I’ve been living my best life hosting our HoppyYumYum101 Series at the brewery, where I get to nerd out with our fans about brewing, beer tasting, and raw ingredients.  This past week, we got together between the rows of fermentors to talk about yeast, the little ladies who make the beer, while CO2 bubbled amiably around us.

Let’s be real here: Saccharomyces cerevisiae, also known as ale yeast or baker’s yeast, is FAMOUS.  This is the species that taught humans about microbes. Before Louis Pasteur’s work in the late 1800s, people (chemists) thought that beer just fermented itself (and that diseases could be cured with leeches, but who’s keeping track).  Pasteur’s famous swan neck experiment – where he showed that fermentation needed not just air but also the airborne microbes that come along with it – changed the way people thought about the world.  We suddenly understood that there were truths to the universe that we couldn’t see with our naked eyes, that we might need other tools to measure.  Which opened up a whole technological adventure to understand things beyond our human perception – diseases, DNA, space, the subtle movement of tectonic plates…

All thanks to our little friends the yeast.

We like to call our yeast the hardest working employees in the brewery because they work day and night to turn sugars into alcohol.  It comes easy to them, though – fermentation is just livin’ for yeast.  They eat sugars and pee alcohol (~44%) and fart CO2 (~44%) and make more yeast (~15%) and fart off some other aroma compounds (1%).  These aroma compounds are really what gives beer its taste and are the main things that differentiate yeast strains from one another.

Brewers yeast can generally be divided into three categories: Ale, Lager, and Wild yeasts.  Ale yeast (Saccharomyces cerevisiae) is called top-fermenting yeast because its vigorous fermentations produce lots of CO2 that pushes it to the top of the tank.  It likes warmer fermentation temperatures and tends to produce lots of fruity, spicy, or sweet esters that add lots of flavor to the beer.  Lager yeast (Saccharomyces pastorianus, named for Louis Pasteur, NBD) likes colder fermentation temperatures and tends to produce low, slow fermentations that are less estery and more sulfury – think a burnt match (sulfur dioxide) or farts (hydrogen sulfide).  Wild yeasts are unpredictable and tend to produce lots of phenols – spicy, medicinal, and smoky flavors.  Some well-known wild yeasts are Brettanomyces (common in French wines), Candida, and Pichia.

Here at Bale Breaker, our house yeast is an ale strain known for clean, low-ester fermentations.  We chose it to showcase all the yummy flavors of hops – citrus, tropical, berry, melon, pine, cedar, YUM!  In order to keep the fermentations clean, our yeast needs to be in peak condition.  Our brewers are like athletic trainers, monitoring performance daily and checking on one of the yeast’s strongest-smelling byproducts – diacetyl – three times over the life of each batch.  Like most brewers, we reuse our yeast for 10-12 generations, and we need to keep it in tip-top shape during that whole time: keeping it from getting too hot or too cold as the situation demands, giving it plenty of nutrients, oxygen, and (of course) lots and lots of sugar to ferment into sweet, sweet alcohol. 

We’re not boring, though.  We like to experiment with other yeast strains and funky microbes in our Imagination Station, the 5-barrel test kitchen that is an exact replica of our 30-barrel production system, where creativity rules.  Right now in our taproom, we are pouring a beer brewed with three different yeast strains – Kölsch (a German ale strain with lager-like characteristics), Belgian Trappist (an ale strain from Belgium with banana and clove-like esters), and Brettanomyces (a wild yeast that produces white wine-like fruity esters and smoky phenols) – called Strange Days Brett Ale.  Come check it out and all the other zany beers from the Imagination Station, which change weekly!

Posted February 22, 2019

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