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Understanding Baking: How Yeast Works
by
Dennis Weaver
Did you ever wonder why flour
tastes like sawdust but a French or Italian
made with that same flour and little else has
a pleasant, sweet taste?
Bread wouldn't be
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
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
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
without retarding? Yes, but retarding does give
it desirable flavor overtones and a more open
crumb.
Copyright 2003-2007,
The Prepared Pantry (http://www.prepraredpantry.com
). Published by permission in the Article
Directory: http://www.articlecube.com
Dennis
Weaver is a baker, a recipe designer, and a writer.
He has written many baking guides and How
to Bake, a comprehensive baking and reference
e-book--available free at The
Prepared Pantry which sells baking and cooking
supplies and has a free online baking library.
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