Long Technical Post 4

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Daniel Wing

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May 25, 1998, 3:00:00 AM5/25/98
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Since many people new to natural leavens would like to bake San Francisco
sourdough, Desem bread, or German rye bread, let's look at some of their
characteristics, as determined by their leavens, ingredients, and
processes.
**

The microflora of German rye sour and Sanfrancisco sourdough is (almost)
identical. The difference is raw material and production process. Prof.
Hammes thinks that L. sanfranciscensis isolated from wheat or rye may have
different properties (e.g. degradation of arginine to ornithine, see
comment No3, or proteolytic activity (see comment No2: wheat has less
proteolytic activity by itself than rye). He still has to prove his point,
though.
-----------------------------------------------------------
That yeast is also resistant to a natural antibiotic made by the bacteria.
**

The most “antibioticł compound in sourdough is acetic acid. Although I
mentionned earlier that Candida milleri from Böcker Reinzucht Sauer (The
Saccharomyces exiguus described by Kline and Sugihara has been renamed to
Candida milleri as well) is more sensitive to acetic acid than the
lactobacilli, it certainly is much more resistant than bakerąs yeast.
Gobbetti says that L. sanfrancisco produces other organic acids that may
inhibit yeast growth, but I donąt know wheter or not the concentration in
the dough is high enough to make a difference. As far as I know, no other
antimicrobial compound in dough has been characterised.
-----------------------------------------------------------
Most German rye bread has at least 30 percent rye
**

I have the figures: 60% is “mixed rye breadł containing both rye and
wheat, but more of the former. As far as the bread goes, rye only about as
important as wheat only. The situation is different for bagels, pretzels,
and so on. There is increasing interest in wheat sourdoughs: the 1 - 5%
addition of sourdough, which is sometimes replaced by a dried and “deadł
sourdough works, but not quite as well as it could. Which is why industry
is funding flavor research at the Universities of Hohenheim and Munich...
----------------------------------------------------------
Vollmar and Meuser showed that the rate of bacterial reproduction after
inoculation is self-regulated, within limits: if you add a small inoculum,
the bacteria will multiply faster than they will if it is larger, so the
static population (say 1,650 million cells/cc) is reached at the same time
in either case, about three and one-half hours.
**
The Vollmar and Meuser sourdough machine is not a very good example: as
pointed out in comment No1, it operates with an inoculum of 50%, which
makes the dough so acid from the beginning on the the lactobacilli donąt
like to grow fast. Between 1 and 20% inoculum, lactobacilli grow at the
same speed (giving rise to the dependency of fermentation time and
inoculum size explained earlier). The Vollmar and Meuser machine also has
a rather high yeast content (if youąve read their publication in Cereal
Chemistry; yeasts are above 100 million or more than 10% or the total cell
counts, while “normalł starters such as the Sanfrancisco starter of the
Böcker Reinzucht Stater have only around 10 million or about 1% of the
total cell count.
--------------------------------------------------------
When cultures are fermented at higher temperatures, non-pathogenic
acid-tolerant contaminants such as Pediococcus (makes too much lactic
acid) and Acetobacter (makes to much acetic acid) can intrude and
dominate, affecting taste.
**

Pediococcus is probably less acid tolerant than L. sanfranciscensis, but
it grows at higher temperatures (as mentionned above, sanfranciscensis
does not like more than 35 - 37°C. Acetobacter is of no importance in
sourdoughs: it strictly requires oxygen for growth, and sourdough becomes
anaerobic (=without oxygen) very quickly due to the metabolism of yeasts
and lactobacilli. If youąve ever seen a vinegar fermenter you will notice
that several hundred liter of air are pumped through a liter of vinegar
during an hour: it is almost impossible to aerate sourdough in such a way.
--------------------------------------------------------------
Dr. Sugihara, who participated in the characterization of the flora of San
Francisco sourdough and several other cultures, was asked whether natural
sourdough cultures could be contaminated with commercial yeast. His reply
was no, not if you have a stable culture that is continuously maintained
with the same conditions and ingredients.
**

Dr. Sugihara is certainly right here. There was an experiment done by a
Dutch group: bakerąs yeast didnąt survive more than two refreshments. I
think that itąs the acetate that kills the yeast as its less acetate
tolerant than sourdough yeasts.
And to the margin note right next (CONCERNING THE ABILITY OF BACTERIAL
FERMENTATION TO RAISE A LOAF OF BREAD, WITHOUT YEAST): Weąve done the
experiments, it works quite well without yeast. The volume is somewhat
smaller, though. Markus Brandt has estimated the contribution of yeasts
and lactobacilli to gas production in a “normalł sourdough: about 50%
comes from lactobacilli and yeasts each. The yeasts are fewer in numbers,
but larger in size.
--------------------------------------------------------
Bakers are interested in the acids produced by leaven microbes because
much of the distinctive flavor produced by leaven microbes comes in the
form of organic acids that are products of fermentation.
**

The production of lactic acid in dough in determined mainly by the
buffering capacity of the flour, i.e. the ash content. Dough yield and
temperature are much less important; as far as Spichers investigations go,
I think that the higher lactic acid concent of doughs with higher
temperatures or higher dough yields he measured is due mainly to the
faster fermentation at these conditions. (this holds true if you calculate
the lactate produced on the amount of flour in the dough: this ratio is
fairly constant). The amount of acetic acid produced is controlled mainly
on the availability of fructose. L. sanfranciscensis produced lactic acid
and ethano (and carbon dioxide) from maltose or glucose. If the organism
wants to produce the more oxidized end product, acetic acid, another
substrate must be reduced. L. sanfranciscensis reduced 2 moles of fructose
to mannitol per mole of acetic acid formed. The ratio of mannitol to
acetic acid in dough os about 1.8, fairly close to the theoretical value
of 2 if fructose was the only co-substrate that is reduced. During
fermentation, L. sanfrancisco starts to produce lactic acid and acetic
acid first, and forms lactic acid and ethanol only if the fructose is
depleted. There is a lot of fructose in dough, but not all of it is
available for the lactobacilli. Yeasts liberate some of the fructose bound
in glucofructans that thus becomes available for the lactobacilli (there
is some nice work that has been done by the Sugihara group, Saunders et
al., cereal chemistry, 1972 or 1973). If you to too high with the
temperature, you slow down yeast growth, and the acetic acid levels in the
dough decrease. For bakers, an easy way to increase the acetic acid
content is to add sugar 8that is sucrose,a consisting of glucose and
fructose). This wonąt increase the total titrable acidity, though, as that
is determined by the buffering capacity. Sugar addition (not too much, 1
or 2%) may speed up fermentation in white wheat flours: as mentionned
above, in contrast to whole wheat flour and rye flours, the enzyme
activities and thus the sugar concentrations are rather low and may limit
microbial metabolism.
As far as the influence of acetic acid and lactic acid on flavor go:
lactic acid has no influence on aroma, only on taste, while acetic acid is
an aroma volatile. So, I think it is not so much the ratio of lactic to
acetic acid, but more simply the acetic acid content that matters.
------------------------------------------------------------
Natural leavens should be actively fermenting and reproducing when they
are incorporated into a dough
**
Yeasts in dough donąt have to rely on oxygen for growth: if that were the
case, they woudną t be there.
----------------------------------------------------------------------
The more accepted and consistently successful way to store a culture for a
month or so is to make a fresh and very stiff storage leaven, put it in a
well covered vessel ...
**

Such leavens may keep up to almost three month (my sister had a baby in
March and didnąt use her starter for almost three month. It was stored the
way you described here, and did come out well upon refreshment. The Böcker
Reinzuchtsauer is also distributed as stiff, refrigerated product. I think
the company does not guarantee storage stability of more than 4 weeks,
though.)
----------------------------------------------------------------------
Still there may be someone out there who does need to start a leaven
because of some terrible misfortune--
**

I think it does not matter when the first batch of a new sourdough stinks
- the good bacilli will come out eventually, and they may come faster if
fermentation is done around 25 - 30°C (as mentionned earlier, the
temperature optimum of L. sanfranciscensis is 32 - 33°C). There has been
nice work done in Rudi Vogels lab on the microflora of a freshly started
sourdough: first, there are Enterobacteria (Escherichia coli, Salmonella,
Enterobacter), highly undesirable organism that stink terribly, then there
are homofermentative lactobacilli (good, but no gas production), then
acid-tolerant, heterofermentative lactobacilli. I think, this took about
48 hours at 30°C. The stink at the beginning does not matter as the
organisms will be diluted out or die eventually. No L. sanfranciscensis,
though, these will occur only after repeated refreshments. Peter Stolz of
the Böcker company told me that it takes about two weeks of repeated
inoculations to get a good “sanfranciscensisł sourdough. I donąt know
whether or not this process was sped up in his case as, due to his
workplace, his skin is all covered with L. sanfranciscensis.
-----------------------------------------------------------------
My biggest disagreement with her, though (NANCY SILVERTON), is about the
amount of material one should use in a starter.
**
I agree with you: one g of dough is one billion lactobacilli and 10
million yeasts: more than enough. In the lab, Iąm doing most experiments
on a 1/10 ml scale, for dough refreshments at home, it does not get much
smaller than 10 g: itąs difficult to handle smaller amounts.
-------------------------------------------------------------
If leaven refreshment intervals are excessive
**

The main criterion of sourdoughs containing L. sanfranciscensis is the
repeated, frequent refreshment (not counted the storage in the
refrigerator). Peter Stolz said that one every 24 hours will suffice, if
intervals are much longer than that (lets say more than 3 days),
different, more acid tolerant organisms may evolve (e.g. L. pontis as
found in the Vollmar and Meuser Breasd maschines: these are refreshed
frequently, but with a very high inoculum).
---------------------------------------------------------------------
Refreshment schedules are always dependent on temperature.
**

See my earlier comment on the temperature dependency of growth of L.
sanfranciscensis and Candida milleri. Most of the typical sourdough yeasts
resemble C. milleri with respect to the temperature sensitivity (i.e. no
growth at 37°C).
-------------------------------------------------------------
Acidity can be expressed as flavor (an acid flavor), as pH, or as total
acidity.
**

That a good explanation of the total titrable acidity concept. (I find
students almost done with their degree still have difficulties with this
concept).
-------------------------------------------------------------------
At any given temperature the thinner starter will ferment faster and reach
a lower pH; but will not contain as much acid.
**

If you calculate the amount of acid produced on the weight of the flour
rather than the dough weight, the outcome -lactic acid per g flour -
should be pretty independent on dough consistency (not if very stiff
doughs are produced: the combined salt and acid stress leads to a
decreased acid production). Markus Brandt observed this in doughs (rye
flour, TA 180) if more than 2% salt were added.
-------------------------------------------------------------------
Together, caramels and Maillard products are responsible for much of the
flavor and aroma of fresh yeasted bread, although of these two, Maillard
products are moch more intensely aromatic.
**

This is right for both yeasted breads and sourdough breads, however, it is
important to note that whatever chemicals are reacting with each other
during baking must be formed during dough fermentation. (Schieberle in
Munich has done several nice studies: he supplied doughs with amino acids
and demonstrated that the levels of aroma compounds in the bread were
increased). So, formation of aroma precursors during dough fermentation is
crucial for the Maillard reaction.
==================
The end of this set of posts-- DCW

--
Dan Wing
Wag...@connriver.net

Dick Adams

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May 29, 1998, 3:00:00 AM5/29/98
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About 4 installments posted 4/25/98 entitled "Long Technical Post"
(1-4) by Dan Wing <wag...@connriver.net>:

Having been duly inspired and mystified by the subject report, I
should like to ask Dan Wing if he will suggest some ways in which
Professor Gänzle's wisdom can be applied in practice to
recreational sourdough bread making.

>...Since many people new to natural leavens would like to bake


>San Francisco sourdough, Desem bread, or German rye bread,
>let's look at some of their characteristics, as determined by

>their leavens, ingredients, and processes...

It would be valuable to have that information summarized as to
pertaining to SF type white sourdough bread, on the one hand, to
German rye bread on the other. (Desem does not seem to be a big
subject at r.f.s.)

I have been particularly amazed by the news that one of Professor
Gänzle's colleagues is apparently counting microorganisms in
dough. To me, that seems like making a census of monkeys and
snakes in the bush (from an aircraft).

---
Dick Adams


defau...@domain.com

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Jun 2, 1998, 3:00:00 AM6/2/98
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Dick Adams wrote

> About 4 installments posted 4/25/98 entitled "Long Technical Post"
> (1-4) by Dan Wing <wag...@connriver.net>:
>
> Having been duly inspired and mystified by the subject report, I
> should like to ask Dan Wing if he will suggest some ways in which
> Professor Gänzle's wisdom can be applied in practice to
> recreational sourdough bread making.
>

The mystic may arise from the fact that the "long technical post" was
written as part of a personal communication and not for a large
"audience": things may have gotten a little bit out of context. As far
as the applicaion to recreational sourdough bread baking goes, it should
contain information as to how acid production in sourdough is
controlled, and how the sourdough starter can be treated to keep the
lactobacilli happy. As the organisms are pretty much the same in white
wheat sourdough and rye sourdough, this information relates to either
one. (To my thinking, the differences in taste between "San Francisco
Sourdough Bread" and other breads are more likely to result from the
different raw material, fermentation and kneeding process and baking
than from the differences in the sourdough starter). As far as other
subjects go - influence of sourdough fermentation and raw material on
aroma and texture - I don't have much more to offer than the fact that
sourdough bread usually tastes better than "straight yeast" bread (which
most of you probably know), and a few working hypotheses.

(By the way, you're a little bit ahead of time as far as my academic
merits go.)

>
>
> I have been particularly amazed by the news that one of Professor
> Gänzle's colleagues is apparently counting microorganisms in
> dough. To me, that seems like making a census of monkeys and
> snakes in the bush (from an aircraft).
>
> ---
> Dick Adams

The counting is a simple method used in every microbiology lab: One
gram of sourdough contains about 2 billion of lactobacilli
(microbiologically spoken, a few hundred million more or less don't
matter). To count, the sourdough is diluted 1 in 10 million ( 7 one in
ten dilutions) and poured in an agar plate. Each of the about 100 cells
of the dilution starts to grow and is visible as a colony a few days
later. Or, to translate to the census of monkeys in the bush: Distribute
the monkeys evenly i n the bush (making sure that they can't mix
afterwards) and wait until the "families" produced by each (pair of)
monkeys is big enough to be visible from the aircraft...


Michael Gänzle

gan...@uni-hohenheim.de


Dick Adams

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Jun 3, 1998, 3:00:00 AM6/3/98
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Michael Gänzle <> wrote in message
<35743CD9...@domain.com>...

>(By the way, you're a little bit ahead of time as far as my
academic merits go.)

Sorry, couldn't wait. We need a Professor right now!

>The counting is a simple method used in every microbiology lab...

So it seems like we can count on Markus' counts.

What I hope for most is a temperature time plot (or other such
instruction) to determine how times should be adjusted for varying
temperatures to get optimum ( culture feeding interval | sponge
development time | rise time ). The data presented seem to give
a few points on such curves, quite similar (in shape and slope on
semi log plots) for yeast and bacteria.

It was interesting to observe that yeast growth relative to
bacterial growth is retarded towards the high and low temperature
limits. So when Andreas tells us the bacteria "like" high
temperatures, he is meaning that they tolerate high temperatures
better than yeast does. No doubt some others will also perceive
that this high, and similar low, temperature behavior may provide
a means to get really sour culture and sponge. (But I can't
imagine why one would need those, since a yeasty culture/sponge
works best, at least for white SD bread.) It also makes it seem
silly that some people advise to "retard" at ~50 F. for
sourness/flavor development, since the effect desired seems to
occur at the practical limits of the temperature time function,
not in the middle of it.

Several things continue to baffle me (well, more than that, but
let's take a few):

If the bacterial generation time is shorter than yeast's
generation time, why doesn't periodically fed starter culture
become all bacteria?

Another baffling thing is the accumulation of acids and other
metabolic products as they may affect growth kinetics. Not only
that, but also the suspicion that bacteria may thrive on yeast
deciduem, which would lead one to suspect that bacterial growth
may accelerate when yeast becomes disadvantaged by its depletion
of its nutrients. These things make it hard to believe that the
compound system may be described by very simple rules.

My practice of maintaining my starter culture (with bi- or tri
weekly feedings ) in the refrigerator appears to defy logic (since
yeast, by Markus' numbers, does not seem to grow at refrigerator
temperatures, though bacterial growth may only be impeded). But I
guess one could assume that my organisms have ( adapted | mutated
| changed | whatever ). SDI's reported practice of maintaining
their cultures in the refrigerator with semiannual feedings seems
perhaps a bit off base. Carl G. seems to have the right idea, as
well as the majority of home SD bakers who incubate their cultures
at warm temperatures after feeding and before returning the
culture to the refrigerator for short, like weekly, intervals.

A third baffling thing is the relationship between number of cells
and activity. It would be nice to be able to assume that the
concentration of microorganisms predicts their activity
(leavening, flavoring, etc.). If one were to attempt to predict
practical parameters from cell count data, some assumptions about
that relationship would seem to be necessary.

Be assured, my esteemed Professor, that there is a world of
difference, in my case, between serious confusion and desire to
pick nits.

(Here in USA, all vat is needed to be a Professor iss to talk a
little bit funny). (Umlauts are good, too.)

---
Dick Adams

P.S. I have still not found the keystrokes for the little
superscript 0 that designates degrees.


so...@spamlesssoleassociates.com

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Jun 3, 1998, 3:00:00 AM6/3/98
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"Dick Adams" <dick....@bigfoot.com> wrote:
»
»P.S. I have still not found the keystrokes for the little

»superscript 0 that designates degrees.

Try ALT-0186 for Dº

--
-Kenneth

If you email please remove the "SPAMLESS."

nos...@auerbach_at_unity.ncsu.edu

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Jun 3, 1998, 3:00:00 AM6/3/98
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In <6l3sm2$j...@bgtnsc02.worldnet.att.net>, on 06/03/98
at 12:11 PM, "Dick Adams" <dick....@bigfoot.com> said:

<- It also makes it seem
<- silly that some people advise to "retard" at ~50 F. for
<- sourness/flavor development, since the effect desired seems to occur
<- at the practical limits of the temperature time function, not in the
<- middle of it.

I would love to know how the technical underpinnings of retarding. The
data are that retarding improves flavor. The question is how? As Dick
now admits, the interaction effects are complication so the old 10
degree/doubling rule tells a minsicule part of the story.

--
Regards,
David


"What would life be without arithmetic, but a scene of horrors?"
-Rev. Sydney Smith, letter to young lady, 22 July 1835

Check out http://www.nyx.net/~dgreenw/sourdoughfaqs.html
for sourdough FAQs

-----------------------------------------------------------
David Auerbach nospam@auerbachatunitydotncsudotedu
fix the above for the real address
-----------------------------------------------------------

Dick Adams

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Jun 3, 1998, 3:00:00 AM6/3/98
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nospam@auerbach_at_unity.ncsu.edu wrote in message
<35759339$3$nhreonpu$mr2...@news.duke.edu

>As Dick now admits, the interaction effects are
>complication so the old 10 degree/doubling rule
>tells a minsicule part of the story.


I admit nothing! I will use the old rule until something better
comes along. Anyway, it is not a rule, but a means of estimating.
The Brandt numbers crudely fit a 5 or 6 degree (ºC.) rule through
a usable range. I am betting on a 8º "rule". These kinds of
rules are for lumping everything, even that which surpasses human
understanding.

---
DickA


nos...@auerbach_at_unity.ncsu.edu

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Jun 3, 1998, 3:00:00 AM6/3/98
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In <6l45fu$p...@bgtnsc02.worldnet.att.net>, on 06/03/98
at 02:38 PM, "Dick Adams" <dick....@bigfoot.com> said:


<- nospam@auerbach_at_unity.ncsu.edu wrote in message
<- <35759339$3$nhreonpu$mr2...@news.duke.edu

<- >As Dick now admits, the interaction effects are
<- >complication so the old 10 degree/doubling rule
<- >tells a minsicule part of the story.


<- I admit nothing! I will use the old rule until something better comes
<- along. Anyway, it is not a rule, but a means of estimating. The
<- Brandt numbers crudely fit a 5 or 6 degree (ºC.) rule through a usable
<- range. I am betting on a 8º "rule". These kinds of rules are for

As I said. The question is "estimating" what? The What that is
estimated is a miniscule part of the story, as we both know.

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