On 10 Mar 2002 at 1:45, Brianjwoody@aol.com wrote:
> The evolution is a result of local airborne yeasts slowly overcoming
> the original. If you start with a San Francisco culture, and live
> there too, it will stay as is for ever (except that local things
> evolve too!). If you start in England with SF, as I did, it will
> slowly change. How slowly depends on how you nurture the culture, but
> change it will. You can freeze some of the original and reactivate at
> intervals, after throwing away the one you have been using. That keeps
> near the original for much longer. Cheers, Brian
There is so much mythology surrounding sourdough that it's often hard to
tell what is going on.
A number of experiments have been done with trying to catch a culture using
sterilized flour. The success rate when using sterilized flour is much
lower than when using plain off-the-shelf flour. Using less processed
whole wheat or rye flours instead of white flour further increases the
chances of success.
This suggests the "culture from the air" theory is likely to be an old
husbands tale. In short, it doesn't seem very likely that yeast or
lactobacillus from the air are that significant.... if starting a culture
from local air is difficult, then there probably isn't enough in the air to
take over a healthy, established culture.
My feeling is that the largest potential source of infection in the culture
comes from the flour added to the starter.
And the greatest chance for the added flour to overwhelm the starter comes
when the starter is not maintained in a healthy condition, or when the
starter is given a very large refreshment.
Under test kitchen conditions starters have remained unchanged for 50
years, and the test isn't over.
So, keep the culture healthy, and don't give it overwhelming feedings.
Mike