From: dadams@cray.com (David Adams)
Subject: Re: more on the biology of sourdough
Reply-To: dadams@cray.com
Organization: Cray Research, Inc.
Date: 25 Aug 92 11:39:14 CDT


Thanks to delwiche@sunflower.bio.indiana.edu (Charles Delwiche) who writes:


| There is,
|however, good evidence that wild taxa can and do invade sourdough
|starters.  For example Loenner et al. (Current Microbiology 20: 201
|1990) found that "during fermentation of bakery sour dough, strains
|other than the inoculated starter gradually became dominant in the
|microflora". 

This is of interest.  It would stand to reason that sometimes this
can work the other way too.  I wonder if there have been any studies
or concerns that importing a new culture to an area might disrupt
the local "balance" of microflora.  After all the concern might
be that some strains or flavors of sourdough might be whiped out.

| This article is also of interest because it studied the
|plasmid content of bacteria in sourdough starter (if you know what
|that means, you might want to look at the paper).  

Can you give us any idea of what it means?

|
|Other studies have looked at fair numbers of starters, and compared
|their microfloras.  Galli et al. (Microbiologie-Aliments-Nutrition
|6:345 1988) looked at 20 starters and found a pretty wide variety of
|lactobacilli and yeast.  In all the cultures they looked at,
|lactobacilli outnumbered the yeast.  Sourdough is like most other
|microbiologically produced foods in that the fermentation is complex,
|with each batch going through an ecological succession of different
|taxa.  In other words some critters start early, but get wiped out
|later on by other more slowly growing critters.  

I have wondered if this is part of the explaination for how the Russian
sourdough culture from SI (which comes from within 25 miles of Moscow)
behaves so differently from batch to batch.  Sometimes it would be
mild and sometimes very sour.  It seemes to go through cycles.  It
does indeed seem to be complex.

|
|For those of you who read German (not me), there is a lot out there
|for you to read.  There is a book that sounds great: Handbuch
|Sauerteig.  Biologie, Biochemie, Technologie [Sourdough Handbook.
|Biology, biochemistry, technology], by G. Spicher and H. Stephan
|(1984), ISBN 3-922528-37-6.  If anyone finds that in English (or
|Spanish) I'd like to have it. 
|

I wonder if you would be able to tell us which of these articles are
most likely to be readable by someone without a graduate degree in
microbiology.  I really wish someone would write a text at the 
introductory level for "Kitchen Microbiology".   I think the subject
could help to get people interested in biology etc.

|I have done a partial literature search, and have two or three hundred
|references on academic studies of sourdough, but I hate to post such a
|thing to the net.  It wasn't at all hard to find these references; I
|basically just went to a CD ROM and typed "sourdough" and "sour
|dough", and up popped enough references to keep me busy.  If you don't
|have access to the appropriate databases, and you want to get serious
|about the sourdough scientific literature, send me direct email, and I
|will upload and email what I have to you.

I did a literature search at the University of Minnesota once on "sourdough"
and I got hundreds of references.  Almost all of them were about the
history of Alaska and the Yukon and on the sourdough wars.  None of them
had anything to do with the making of bread.  I say that your listing
is worth posting, especially if it is actually about the microbiology or
about making bread etc.


|One practical thing I gleaned from the literature:  be really careful
|with the salt concentration in your starter and dough.  The salt
|concentration can have an enormous influence on the leavening
|capabilities of your sourdough (see Galal et al., _Cereal Chemistry_
|55:683 1978).  If you are trying to cut down on your salt, better not
|do it by leaving the salt out of your dough.  At least that is what
|the literature says, and it is consistent with my own baking
|experience.  What have other people found?

I had read that salt helps to regulate the growth of yeast.  Laurel's
Kitchen Bread Book discusses the difficulties of making bread without
salt.  (And that is with active dry yeast.  I can imagine that things
might be more difficult with more complex cultures.)


|----------------------------------------------------------------------------
|Charles F. Delwiche, Dept. of Biology        |"We admit no more causes...
|Indiana University, Bloomington, IN 47405    |than such as are both true
|                                             |and sufficient." I. Newton




--David C. Adams  Statistician  Cray Research Inc.  dadams@cray.com
___________________________________________________________________
       member--Minnesotans for Global Warming.

Newsgroups: rec.food.sourdough