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Old 12-09-2006, 05:48 PM posted to
Mike Avery Mike Avery is offline
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Default yeast/bacteria balance

Jeff Miller commented:

My understanding has always been that no matter where the culutre came
within a couple of months, your local microflora will take over in your
starter. If that's true, then that would explain why your cultures change
their flavor characteristics.

Is this true? Or am I repeating a sourdough urban legend here?

A commonly asked question is, "will my starter change when I move it?"
with its corollary of, "When I moved from St. Louis to Poughkeepsie, my
starter changed, what happened?"

There are more old husbands tales surrounding sourdough than almost
anything else I've been involved with, with the possible exceptions of
high-end audio and brewing.

Dr. Michael Gaenzle of the German Cereal Institute studies sourdough
starters and says he has starters that the institute has had for over 50
years that have not changed in that time.

Somehow, I can still hear someone saying, "Yeah, but my starter doesn't
taste or work the same as it did before I moved!"

There are lots of factors at play here, so it's not as simple and
straight forward a topic as you might find in a biologist's lab slants.

Before I get too far into the discussion, I'll preface my comments by
saying that all the comments apply to a healthy culture. And that many
hobbyist's cultures are on the ragged edge of death. Good culture
maintenance is very important.

Almost all cultures, whether a hobbyist culture or a professional
baker's culture are impure cultures. There are around half a dozen
yeasts and three or so lactobacillus strains that can make a viable
sourdough culture. Most of our cultures have many of these in them, but
one strain of yeast and one strain of bacteria are dominant. If we
change how we handle our cultures, we can change which strains are
dominant. And the taste and activity of the culture can change.
Sometimes this is good, sometimes it isn't.

Changes in cultures, absent changes in feeding habits, are unlikely, for
the same reason that most experienced sourdough practitioners discount
the "starter from the air" theory. If you look at the count of yeast
and bacteria in a volume of air, and compare that to the count in a gram
of flour, it's obvious the odds favor the flour being the source of the
culture. Dr. Ed Wood in his "World Sourdoughs From Antiquity" book
recounts an experiment he did for National Geographic wherein he tried
to capture an authentic Egyptian culture from the air. He irradiated
the flour so it would not have anything alive on it. In a lower-rent
fashion, a number of people in tried to get local
cultures by pouring boiling water over the flour to try to sterilize
it. In both cases, the experienced people went from nearly universal
success at starting a culture to a very high failure rate. This
corroborates the idea that most cultures are started from the flour, not
from the air.

Similarly, the yeast and bacteria count in an active starter is much,
much higher than the count in flour. A large part of the stability
researchers, such as Dr. Gaenzle, report in cultures is because the
lactobacillus bacteria produce a number of chemicals to kill would-be
invaders. The acidity of sourdough starter is just the front line of
defense. So, it seems very unlikely that a healthy starter could be
taken over by the yeast and bacteria found in either the air or flour.

Now then, if you've been taking good care of your culture, what could
make the bread made with it taste different? Hunters prize boars that
have been feeding on acorns - it gives the meat a great taste (or so I'm
told - if you want to send me a care package, I'd love to try some!)
French farmers force feed their geese special herbs and spices to give
the pate made from the livers of those geese special tastes. Many
nursing mothers report that when they eat this food or that, their
babies no longer like mom's milk. If more complex organisms change
their taste, or the taste of things they produce, based on what they
have been ingesting, is it any surprise that yeast and bacteria would
also change their taste, and the taste of the breads they produce, based
on changes to their diet?

There are regional differences in flours, even when the brand name on
the sack is the same. Different flours taste different. And it seems
that yeast and bacteria notice differences we don't.

Try converting your starter from white to whole wheat or rye flour.
There are very rapid changes to the aroma and taste of the starter, well
beyond what you'd expect from the changes in the flour.

A number of experienced sourdough bakers have said that the key to
copying another baker's bread isn't getting their sourdough starter, it
lies in finding out what kind of flour they are using.

So, if your starter changes, maybe you need to send back to friends who
didn't move and ask them for care packages of your old standby flour.
Or just get used to the flavors that the flavors in your new home produce.


....The irony is that Bill Gates claims to be making a stable operating
system and Linus Torvalds claims to be trying to take over the world...

Mike Avery mavery at mail dot otherwhen dot com
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