>Hey listen, Roy,
I am all ears Dick
>Over there at http://groups.yahoo.com/group/=ACSourdough/ they are
>explaining to one another how to make barm. Why don't you jet
>yourself over there and teach them some rocket science?
Maybe some other time Dick,

>Below is a recent posting (given there as a non-attributed quotation).

>I thought it might have been due to Jeff Renner (a historic r.f.s.
poster)
>but I wonder if he would have exactly said some of those things.
Thanks for that Dick!
>Roy, I would like you to critique the article, and tell us, and them,
if you
>feel that any corrections could be usefully made. The article is by a

>beer maker, and, as you know, next to rocket scientists, they know
>the most.
Hmmn .....let's see...
"How are the sourness and leavening of starters related?
>There have been several posts over the last little while asking the
>same question in different ways - how are the sourness and leavening
of
>starters related? Some starters seem too sour, or not sour enough, or
>have lost their sourness, or are sluggish or too active (not a problem

>for most) and folks want to know how to manipulate this. It also has
>been pointed out that lactobacilli are anaerobes, but this needs
>expansion. Here are some thoughts on this.
>I am a homebrewer, and have read a good bit about yeast growth. Baking

>and brewing yeast are just different strains of the same species, but
>wild yeasts are different species, and some are even different genera,

>so this may not apply to all, but I suspect it does.
He is right the same specie what we call Saccharomyces Cereviseae is
the name for bakers, brewers, wine and distillers yeast but with a
subspecie that specifies the particular strain.
Brewers yeast varies: if its top fermenting of ale yeast that is called
saccharomyces cereviseae that is the ancestor of our bakers yeast.
This answers the question that wild yeasts that is present in
sourdough can contain also the hardy and acid tolerant type of
saccharomyces cereviseae in combination with Candida Millerie in some
sourdoughs starter cultures.
The other yeast known as lager yeast or bottom fermenting yeast is
called by the name Saccharomyces uvarum, which was nicknamed by the
Carsberg beer as Saccharomyces carbergensis.
>Cultured yeast needs oxygen to reproduce, so once it has depleted the
>oxygen in a starter/sponge/dough, it has pretty much reached the
>population it's going to have. After this, it shifts its metabolism to

>anaerobic. Assuming that wild yeast are much the same, this means that

>letting a starter or sponge sit longer is not going to result in much
>more yeast, and therefore will not increase its leavening power. It
>will become more sour (see below).
Yes, I think most yeasts can act both as an aerobe and anaerobe. The
use oxygen for growth but does not need it for fermentative activity .
>Lactobacilli are facultative anaerobes (as opposed to obligatory
>anaerobes), so they will continue to metabolize and reproduce *either
>with or without oxygen*.
Yes
>However, they only produce lactic acid once
>the oxygen is depleted, resulting in a more sour starter/sponge/dough
>the longer you let it sit. I don't think you need to worry about
>excluding air - the surface above the sponge or whatever is full of
CO2
>from the yeast, so very little oxygen is going to diffuse into the
>sponge, especially if you have it covered, and this will keep it from
>drying out, too.
Hmnn in some point he is right but partially ,,,,, he is thinking only
of the homofermentative microbes that produces only lactic acid, he
missed out the heterofermentative cittters which are significantly more
important in sourdough which can produce aside from weak acid lactic
but also a stronger acid , acetic acid as well
>What does this all mean? If you want a maximally active culture, whip
>all the air you can into it each time you build it. I add the water
>first and whip this thin batter to a froth with an electric mixer,
then
>mix in the flour. This results in maximum yeast reproduction. Then, as

>soon as it has used up all this oxygen, I build it again. Of course,
>it's hard to tell just when this is, but I generally let a sponge go
>until it just begins to fall. If you want a more sour bread, let
either
>the starter/sponge/dough go longer. I find that with high protein
flour
>such as bread or hard whole wheat, the dough can withstand two full
>rises before shaping into loaves, resulting in more flavor (not just
>more sourness, but that, too).
Yeah, ...That is the logic why certain bakeries that use Liquid
starters refresh their culture only once a day( like I mentioned in my
previous post in this NG) which is contrary to most of the hobbyist
experience as they have to refresh their starter twice or even thrice
a day!.
But unfortunately he missed to apply his reasoning on the economic
feasibility of one day refreshment if he can only managed the
fermentation rate properly by temperature control just like what I
elaborated in my previous posts.
They are virtually wasting flour and their time by not economizing on
the available nutrients that are still present in the substrate. An
occasional aeration can go a long way in enhancing the yeast activity!
Some sourdough and fermentation scientists may disagree on this
scanty refreshment technique ,but they have to visit those bakeries
who has been practicing these technique for years and see it with their
own eyes , simulate those techniques in their laboratory, scale it up
the tests and statistically analyze the data ( and by all means
)humbly reconsider rewriting their ideas about the still undocumented
technique related to sourdough fermentation=20
Roy