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On Yeast: A Brief Note

Have you ever given much though to yeast? Do you know what it is? Besides being a leavening agent for the best kinds of bread, I didn’t know much else, myself. When I set out to do a brief study on it, I was not prepared for the firehose of information. As an avid baker and hopeless worldbuilder, I thought it would be good to grasp at least a basic understanding of this mysterious agent and its history. After all, if I want to write food into my books, it’d be good to be accurate, right? Right??

Research, y’all. Research is a rabbit hole.

So what, exactly, is yeast? In a sentence, yeasts are eukaryotic, single-celled organisms of the fungus kingdom. (Eukaryotic is a fancy word that means their cells have a nucleus). Neat, huh? Yeast is fungus. Like mushrooms. But different.

The word ‘yeast’ is derived from the Old English ‘gist’ or Middle German ‘gest’ , which means ‘dregs’ or ‘dirt’, ‘jest’, which means ‘foam’, Old High German ‘gesan/jesan’ meaning ‘to ferment’, and likely the Indo-European root ‘yes-‘ , which means ‘boil’, ‘foam’ or ‘bubble’. In a nutshell, yeast was named after what it looked like and what it did: ferment!

Fermentation is the process of yeast converting carbohydrates/sugars to carbon dioxide and and alcohols (like ethanol!) These wee organisms gobble up the sugars and blow those bubbles that make our bread light and poufy instead of dense weapons for culinary bludgeoning. (The gases smell really good, but evaporate during baking, so do not fear!)

When you think of yeast, chances are your brain immediately jumps to bread baking (mine does, too), but there are over a thousand recognized species of yeast that exist, live, and work in all kinds of environments for all kinds of purposes. Some good (fermented foods & beverages (including kombucha & Kiefer), digestion, etc.), some not so great (i.e., infections). But in regards to bread baking, the primary target of my focus, there are a few neat things I learned.

• Yeast has been used to leaven bread across the Old World for thousands of years before people put it under the microscope and gave it a Latin classification.

• Yeast wasn’t really commercialized until the 1700s, and then it was largely for brewing, which is interesting because,

• For a loooooong time bakeries and housewives used the yeasty foam/scum—barm—left after the fermentation for beer, wine, and feedstock for distilled spirits to bake their bread, which never crossed my mind before. But it so happens that the species saccharomyces cerevisiae, which converts carbohydrates/sugars into carbon dioxide and alcohols (fermentation), common in brewing, is also what we use for bread baking. (Sourdough is a bit different, since that’s the process of wrangling wild yeasts in a mixture of grain flour and water. These are more diverse and unpredictable in species and entirely subject to environment. But delicious).

• Production of baker’s yeast as we know it today didn’t really begin until the 19th century, and was influenced by the change of brewing methods (from a top ferment to a bottom ferment, which limited the supply of bread making yeast. Terribly rude.)

• Louis Pasteur, that guy who invented the dead milk in our grocery stores, had a hand in advancing methods for culturing pure strains, minimizing and essentially eliminating contaminates (bacteria) found in the yeast goos people had been using for hundreds of years. Around the turn of the century, centrifuges were used to concentrate the yeast, and slurry yeast (yeast cells suspended in a medium) became cream yeast became compact (or cake) yeast, and thus was born modern industrial yeast production.

• Fleischmann’s yeast company developed the granulated active dry yeast (and its subsequent forms) we now commonly see on store shelves during WWII. It doesn’t require refrigeration, has a long shelf life, and rises bread faster than other forms—perfect for the war effort.

Fun Fact: Natural yeast that grows on grape skins will automatically begin fermenting grape juice into wine (that’s why you get drunk hornets on your overripe grapevines. It’s hilarious.) But isn’t that awesome how God designed creation to work that way?

Another interesting note about yeast (from reading, but also experience), is that there are compounds in yeast that are responsible for the aroma and flavor of your bread! The longer you let a yeasted dough sit—the slower you let it ferment—the better your bread will taste (it also improves the texture, that’s why pizza dough is best made a couple days in advance and kept in the fridge).

Y’know, in case you were wondering.

Pretty cool stuff, no? It’s fascinating to learn about how God created our world in such intricate ways that we don’t often think about. My favorite discovery was the use of barm from brewing to leaven bread. Until I read about that, I thought sourdough was the only way! God is so cool, working all that stuff together. Now I want to get my hands on some barm and experiment leavening some bread with it!

Is there anything here you found particularly interesting or helpful? Have you ever heard of barm or worked with sourdough? What’s your favorite bread to eat/make?

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