In response to my previous posting Breadmaker Jewish Rye Bread, SeaBee asked:
Shouldn't there be some sugar involved somewhere?
Now, I'm not sure if this is a specific questions because SeaBee thinks that Jewish Rye Bread should be sweet(er), or a more general question like:
I notice in your posting on Breadmaker Jewish Rye Bread there is no sugar. I thought that yeast needs sugar to digest in order for the bread to rise. How can a bread recipe work if there is no sugar in it?
I have chosen to answer the second question.
You are right that yeast digests sugar and produces carbon dioxide and alcohol, both of which contribute to the rise on bread. And, yes, many recipes use sugar (white or brown) or honey or some other sugar to feed the yeast, but that is not the only source of sugar.
By weight, bread flour is about 72% starch, 12% protein, and 13% water. The rest is made up of some sugar, minerals, fiber and other matter. All-purpose will contain a slightly higher proportion of starch, and cake flour even more. Starch is nothing more than a long chain of sugar molecules joined together in a string to make one larger molecule.
Wheat flour also contains two important enzymes, amylase and diastase, that convert starch to sugars that the yeast can digest, so even without adding sugar it is possible to get the bread to rise. Many bread recipes such as traditional baguette and pizza are made simply with flour,water, yeast and salt, and no sugar at all. Other recipes add diastatic malt, which contains diastase to encourage a faster breakdown of starch to sugar.
Many commercial bread flours contain added enzymes to encourage the breakdown of starch to sugar.
As explained in Raising Bread, recipes made without sugar usually take longer to rise and tend to develop more complex flavors than doughs made with sugar.