How Does Baker's Yeast Work?

The magic microbe that makes bread rise and beer alcoholic is yeast -- often, the species Saccharomyces cerevisiae. Learn how it works in this episode of BrianStuff, based on this article: https://recipes.howstuffworks.com/tools-and-techniques/yeast.htm

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Episode Transcript

Speaker 1 (00:01):
Welcome to brain Stuff, a production of iHeart Radio, Hey
rain Stuff, Lauren bogobam here. If you're making a raised
baked good, there are a few ways you can achieve
that height. Quick breads like muffins use chemical leaveners like
baking powder. Cookies, bars, and cakes often use whipped eggs

(00:21):
or creamed butter and sugar with tiny pockets of air
carefully beaten in. But many breads and rolls use a
living ingredient to get that rise. Yeast. This single celled
organism is integral too many a baking process, transforming a solid,
dense ball of dough into a soft, risen loaf. But

(00:44):
not all yeast is the same. There are more than
one thousand, five hundred recognized species of yeast in the world,
with the first known types dating back hundreds of millions
of years. Today's primary baking yeast species is Sacchara mices
sera vizier. It's responsible for two of the tastiest yeast
related food products out there, bread and beer. But how

(01:07):
can a tiny organism only visible with the microscope create
two of the world's most beloved meal time staples, and
is baking with yeast as intimidating as it seems. Let's
back up a step. A yeast is a single celled
fungus related to mushrooms. Yeast used by bakers, s seravisier

(01:28):
is known as a sugar eating fungus. Simple sugars like sucrose, fructose, glucose,
and maltose helped the yeast thrive, and once metabolized, the
sugars ultimately lead to risen bread. The process is known
as alcoholic fermentation. When you mix flour, water, and yeast together,

(01:48):
the yeast eats these simple sugars in the flour and
poops alcohol, carbon dioxide bubbles and molecules that we consider
flavor into the doughy mix. The carbon dioxide bowls can't
escape the elastic dough, so instead they cause it to rise.
When you bake that dough, you're firming up the matrix
of proteins like gluten in the dough around those air bubbles,

(02:12):
resulting in what we know as fluffy, tender yeast leavened bread.
There are two primary types of baker's east on the market.
Active yeast and instant yeast. Both come to you dried
and granulated in small packets, but each brings something slightly
different to the table. Active yeast must be activated with

(02:32):
warm water before using instant yeast can go straight into
your dough and get to work. The fermentation process with
active dry yeast takes longer than with instant yeast. This
can lead to subtly different flavors and breads made with
active yeast over instant. For the article this episode is
based on, has to Work, spoke of Kelly Olson, a

(02:54):
representative for the company Red Star Yeast. She said, when
yeast has more time to work the dough, more flavor
and a better texture is developed, and so there's some
benefit to the more moderate active dry yeast. But then
there are other products where instant yeast is very favorable
as well. Instant east is more shelf stable than active

(03:15):
yeast and provides more consistent results over time, which is
great when you're baking in bulk or when you're looking
for a more mildly flavored baked good. But you don't
technically have to buy yeast. You can make your own.
When people made bread in ancient times right up through
the mid eighteen hundreds, they may not have known what
they were doing, but they were making their own yeast.

(03:39):
The same goes for you making a sour dough starter today,
you simply mix equal parts filtered water and flour and weight.
If conditions are right, naturally occurring yeasts that live in
the air around us, we'll get to work and grow
a colony that you can then use to make bread.
Often throughout history, bread makers would get a little help
from beer brewers. Sometimes these workers were one and the same.

(04:03):
Baker's used balm the frothy east colony left over from
brewing beer as a starter to raise their breads. Brewers
at the time we're capturing wild yeasts as well by
letting their beers ferment in open containers. But these wild
yeasts are different from the packets of Baker's east available
in stores. Olsen said. A commercial yeast is made from

(04:26):
a pure strain of Saccaro Mices seravisier. When you try
to make your own yeast, you're actually getting wild yeast
that's not necessarily from sacaramceas servisier. You're not getting pure yeast,
and you're not necessarily getting something that's consistent or that
will perform the same as commercial yeast. That unpredictability, both

(04:47):
with wild yeast and even with store bought yeast is
one reason why yeast can intimidate bakers, but Olson, who
feels numerous calls for Red Stars East customers, says Baker's
East isn't a scary as it seems. She explained that
it really comes down to watch in your dough while
it rises, versus sticking solely to your recipes timetables. She said,

(05:09):
I always encourage people to go by the look and
feel of the dough. I use the recipe as a guide,
but realize that things can vary from batch to batch,
and so it's best to go by what the dough
is doing. And yes, brewers and winemakers also use s
Seravisier and other yeasts to create alcoholic beverages. In beer,
yeast eats the sugars in malted barley to create alcohol,

(05:32):
carbon dioxide bubbles and flavors. S. Sarahvisier is the go
to for ale style beers, while another species, Sacchara Mices pastorianis,
is typically used in laggers, and recently brewers began experimenting
with wild yeasts again. In wine, yeast is already present
on grape skins, but most winemakers also add a pure

(05:54):
culture like s seravisier to ensure that their fermentation occurs reliably.
The yeast is very particular and easy to kill. In
temperatures of a hundred and twenty degrees fahrenheit or forty
eight point eight celsius or higher will start killing it,
but the cultures can go dormant and then be rejuvenated
down the road, even if that road covers five thousand years.

(06:17):
One egyptologist uncovered yeast microbes in ceramics from over five
thousand years ago. He and his team extracted the yeast
then baked bread with it, resulting in a successful sweet
sour dough. Today's episode is based on the article yeast
is the Magic microbe that makes Bread Rise on how

(06:39):
stuff works dot com, written by Stephanie Vermillion. Brain Stuff
is production of iHeart Radio in partnership with how stuff
works dot Com and is produced by Tyler Klang. Four
more podcasts my heart Radio, visit the iHeart Radio app,
Apple Podcasts, or wherever you listen to your favorite shows.