In the days before commercial yeast, the most common riser was
sourdough. You can start your own sourdough starter the way the
first bakers did. Mix flour and water and let nature take its
course. As an aside, the concentration of yeast on the flour is much
higher than in the air, so despite the romance starters are more
often started from the yeast and bacteria on the flour than from the
air. Historically, cultures were carefully maintained since the
people didn't know entirely what the mechanism behind creating a
starter was. Better to save it than have to start over.
The next most common source of yeast was fermenting beer. This is
called barm. Barm is NOT a sourdough process. Barm is the
anti-sourdough. If you get sourdough bacteria in your beer, you
won't like the beer much. Early brewers learned that if you took
some of the last batch of beer and poured it into the current batch,
it would start fermenting faster. Over time, there was a selection
for the yeasts that worked.
In general, if you start a flour water culture, and if you maintain
it and keep feeding it and using it, it will turn into a sourdough
culture sooner or later. Usually sooner.
For more details, you might check out my web page
<http://www.sourdoughhome.com>
Mike
*Bake With Mike <http://www.bakewithmike.com>*
Mike Avery
A Randomly Selected Bread Saying Of The Day:
"I understand the big food companies are developing a tearless onion.
I think they can do it--after all, they've already given us tasteless bread."
-Robert Orben