From: dixon@spot.Colorado.EDU (Life is real?)
Subject: Re: sourdough ecology clarification
Organization: University of Colorado, Boulder
Date: Sat, 29 Aug 1992 17:04:47 GMT

In article <BtpM7z.CEL@usenet.ucs.indiana.edu> delwiche@sunflower.bio.indiana.edu (Charles Delwiche) writes:
>In article <1992Aug28.113031.15118@hemlock.cray.com> dadams@cray.com writes:
>>In article u4@usenet.ucs.indiana.edu, delwiche@sunflower.bio.indiana.edu (Charles Delwiche) writes:
>>|Just a quick corection:  I stated, or implied, somewhere along the
>>|line that yeast produce amylase, the enzyme that digests starch and
>>|breaks it down into sugars.
>
>>|Sorry if I confused anyone.
>
>To this David Adams wrote:
>>
>>Well this gives me an added point of confussion, since by my understanding,
>>which may well be wrong as I am a layman here, the grains do not release
>>amylase until the process of germination begins.
>
>I probably should have just stuck with my original argument, but now
>that I have gotten everyone, including myself confused, I went and
>looked it up.  The enzyme in question, alpha-amylase, is apparently
>indeed not produced by _Saccharomyces_, either by _S. exiguus_ or _S.
>cerevisiae_.  David Adams is right; the amylases in grains are not
>generally released until germination has begun.  At least this is what
>one is always taught.  One makes malt by taking barley, moistening it,
>
> [stuff deleted]
>
>None the less, in the San Francisco sourdough process, amylase becomes
>active without germination of the grain (Saunders, Ng, and Kline,
>_Cereal Chem._ 49:86.  1972).  They incubated an *acidified*
>flour/water mixture (pH 5.0) and found a marked increase in maltose
>content.  I wonder if the acidification is essential?  It helps,
>because it inhibits the microorganisms already present in the flour,
>but it *might* also help activate the enzyme (I just don't know).  If
>you tried to do this without acidifying the mixture you would end up
>with a big fungal mycelium, or with a nice sourdough starter, depending
>upon how lucky you were.  I think that the total amount of maltose
>released is small compared to what you get in malted barley, where
>almost the entire endosperm (what we eat) is converted to sugar.
>
>So you can make sourdough without adding sugar because sugar is
>produced during the development of the starter.  The lactobacilli
>don't use up all of the maltose produced, so there is enough to add
>flavor to the bread, and also help the crust brown nicely.  There are
>also enough sugars other than maltose produced that _S. exiguus_ can
>grow.
>
>I don't know to what extent this applies to other kinds of sourdough.
>I'll be looking into that when I have some time.
>
>----------------------------------------------------------------------------
>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

Well, now I'm confused again...Is there or isn't there an active sugar-
producing enzyme in flour?  Can yeast utilize starch at all, or can
yeast only utilize sugars?  You may explain how sourdough works, because
it's acidic, but commercial yeast isn't (is it?) and it feeds on flour
just fine.  If yeast can only utilize sugar and there *is* an active 
sugar-producing enzyme in flour, then where did the enzyme come from if
not from germination?  Or are there other sugars in flour that exist in
the wheat berry *before* germination, thereby allowing the yeast feeding
cycle to begin?

Brian D.
dixon@spot.colorado.edu


Newsgroups: rec.food.sourdough