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Understanding Baking: How
Yeast Works
By Dennis R Weaver
Did you ever wonder why flour
tastes like sawdust but a French or Italian bread
made with that same flour and little else has a
pleasant, sweet taste?
Bread wouldn't be bread without yeast and yeast
can't work without sugars. Yeast is alive—living
organisms—and living organisms need food for fuel,
in this case, simple sugars. But flour is mostly
starch and table sugar (sucrose) is too complex for
the yeast before fermentation. Amylase and invertase,
enzymes present in the flour or created by the
yeast, break down the starch molecules into sugars.
Some of these simple sugar molecules become food for
the yeast; others create the sweet flavor we find in
a fine bread—even a French bread where there is no
sugar added.
As the yeast feeds on the sugar, it creates two
digestive byproducts—alcohol (ethanol) and carbon
dioxide. The carbon dioxide is what leavens the
bread—carbon dioxide gases filter through the dough
creating loft. The alcohol is evaporated in baking.
The biological and chemical actions taking place as
the bread ages and rises are called fermentation.
Generally, a long, slow fermentation makes for
better flavor, texture, and moisture retention. Many
fine breads call for “retarding” or slowing down the
growth of the yeast with refrigeration. If dough is
refrigerated, the yeast grows more slowly.
Fermentation still takes place as the amylase
enzymes work within the dough and sugar is released
albeit at a slower rate. When the dough is warmed
and the growth of the yeast takes off, there is
plenty of sugar present for the yeast and an excess
of sugar to sweeten the bread.
When yeast grows more slowly, we find the richer,
fuller flavor of breads made with retarded dough. In
the previous article, we discussed a focaccia that
uses refrigeration to slow down the growth of the
yeast and create the desired crumb and flavor. Is it
a good bread without retarding? Yes, but retarding
does give it desirable flavor overtones and a more
open crumb.
Read on for the printable version of How Yeast Works
>>
This article was taken from
About Baking: Ingredients and How They Work and is
available free for download.
©
The Prepared Pantry
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