Allen Cohn asked Bob,
>Are/were you feeding all these starters with the same flour? Perhaps
>it's not the same air that's making them all start to taste the
>same, but rather the same flour. The literature I've read says that
>all flour has some microorganisms attached...so perhaps in time the
>organisms in your flour come to outnumber whatever different strains
>used to be in your world tour of starters.
I've thought about this topic a lot, and done more than a bit of
research on the matter. If you look at the romance of starting a
starter, many people feel that you catch a starter from the
air. More recent information suggests that while it is not
impossible to do this, it is very unlikely. The concentration of
yeast and bacteria on flour is much, MUCH higher than what is in the
air. Dr. Ed Wood wanted to catch a :"real" Egyptian starter, so he
had some flour sterilized by having it irradiated. When he put out
containers of water and flour, he had a very high failure rate. When
some people in rec.food.sourdough wanted to replicate this, the
poured boiling water on flour to have a poor man's
sterilization. And they found that they had over a 90% failure rate
in starting starters, where normally they took success for granted.
So, the critters ARE on the flour, and will most likely be the source
of a starter.
Similarly, the concentration of critters in an active and well
maintained starter is many orders of magnitude higher than on
flour. It is unlikely that the critters in the flour will take over
a culture. Cultures tend to be, if well maintained, very stable over
long periods of time.
So where do changes in flavor come from? There are two major areas
where change can come in. If you, like most people, have a natural
starter you started with flour and water, it is a blend of different
strains of yeast and bacteria. (In Germany, it is common practice
for a baker to order the exact strains s/he wants from a bakery
supply house and have a very pure culture.) In the natural culture,
over a period of time one strain of yeast and one strain of bacteria
will become dominant by orders of magnitude. The rest are still
there... biding their time. If you change the conditions under which
you maintain your starter, the dominant strains can become minority
strains, and the starter will change. An all too common example of
this is when strains that produce lots of proteolytic enzyme take
over a culture. Proteolytic enzymes break down protein. A little of
this is not a bad thing, it makes the dough extensible. A lot of
this is very bad, it turns the dough into soup. These bacteria
become dominant when the starter isn't fed enough and the critters
that can eat protein instead of starches have an advantage. (As an
aside, starters that go down this path are best discarded. You can
partially rehabilitate them, but the next time you skip a few
feedings, the balance will change and the proteolytic enzyme
producing bacteria will be back in the drivers seat.
If we assume good starter management, where do changes in taste come
from? Hunters prize boars that have been feasting on acorns - it
gives the meat such a nice taste. (Or so I am told. If anyone can
send me care packages so I can try this treat myself, please send me
an email. And French farmers feed their geese special herbs to give
the birds livers a great taste that will be in the pate the livers
will be used in. If you have ever nursed a baby, or lived with
someone who has, you have probably noticed the baby is sensitive to
what mom eats. What mom eats is expressed in her milk. And the baby
may decide not to feed until the baby is really hungry or that taste goes away.
If what a large organism eats can affect the taste of the organism,
or its products, in a fairly short time frame, we shouldn't be too
surprised that what a sourdough culture is fed will affect its taste.
Flour is a commodity, but it is not as standardized as salt or sugar.
There are differences from brand to brand, season to season and mill
to mill. So, even though the sack has the same name on it, the flour
may not really be the same. If you want to see a dramatic example of
the differences flour can make, switch your flour to, or from, whole
grain flours. In just a few feedings, you'll see and smell amazing
differences. The differences between brands of white flour will be
more subtle, but they will be there. An independent confirmation of
this is the baker's folk wisdom that says if you want to duplicate
another baker's bread, don't try to steal his sourdough culture, find
out what kind of flour he is using. Flour is the biggest part of
bread, so this isn't a big surprise.
Mike
Mike Avery mavery at mail dot otherwhen dot com