Allen Paul W. Industrial Fermentations
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BREAD-MAKING 141
The manufacture of bread in 80% of large commercial bakeries
is by the straight dough method. It is a very different process from
maMng bread in the home. Each step is standardised as to tempera-
ture,
time and amounts. The objeot is economy of operation, economy
of material, fuel, labor and space. The resulting bread, however,
must sell and therefore must be of good quality. Yeast and flour act
differently in large quantities. Large ovens bake differently than
small ones. Continuation of operations for the purpose of economy
has to be considered in large bakeries. Baker's bread is the result of all
these considerations. An art of bread-making on a large scale by
Bg
ootrtetff
of
Jabwy
Pro*,
Tha.
18.—Mechanical dough divider.
machinery has been developed. Many bakers advertise "bread which
has never been touched by human hands."
In building a large bakery, the interior is arranged to fit the process
of bread-making. The bread constituents often go from the top floor
by gravity to the mixers. The dough from the mixers also moves
by gravity on through the process until the finished product is wrapped
by the wrapping machines and dropped into shipping baskets. Storage
of flour for the purpose of ageing it is practiced by most large bakeries.
The top floor is often used for this purpose. The flow of materials
through the process from flour to finished product is often as follows:
Ageing, sifting, blending, mixing, fermenting, dividing, rounding,
proofing, moulding, baking, oooling, sealing.
142 INDUSTRIAL FERMENTATIONS
What goes on while flour is ageing is a matter of
By
eovrtety
of
Amerlem Oven and
UOOMM
Company.
Fra. 19.—A battery of dough mixers.
of the wheat and the baoterial enzymes are acting slowly in the
direction of preparing the gluten for the breaking down process.
The sifting and blending of flour have no biologioal significance.
PIG.
20.—Ovens of Whiteaide Bakery, Louisville, Ky.
The mixing of the water, flour, yeast, salt and flour-improvers is
an important step from the standpoint of yeast action in bread-making.
Whether the "straight dough" or "sponge and dough method" iB
used, mixing is very important and few bakeries mix thoroughly enough
to get the best results. The yeast cell aggregates are broken up best
by thorough mixing. Most bakers dissolve the yeast in tempered
BREAD-MAEJNO 143
water before adding it to the dough. The pains taken in thoroughly
dissolving the yeast in the water is well repaid by improved results.
The yeast cells should enter the bread, divided into aa small groups
as possible, and preliminary dissolving and shaking up of the yeast
cake aids this cell separation greatly. Mixing thoroughly gives further
breaking up and also disseminates the yeast cells throughout the dough.
Each yeast cell produces gas from the sugars of the dough, and gener-
ates the gas as small bubbles in the dough. The smaller the aggregates
of yeast cells the smaller the gas bubbles will be. The gas from large
aggregates of "cells collects in large bubbles. Where the yeast cell
aggregates have not been properly broken up and disseminated the
gas bubbles oollect and cavity formation in the finished loaf is often
the result.
After fermentation the dough is passed through the divider to cut
it into proper amounts for loaf making. These pieces then go to the
rounder which rounds them so that proofing w^ll take place uniformly
in each bunch of dough. From the rounder the balls of dough are
conveyed into the enclosed proofer where they are carried back and
forth until they have raised properly. When the dough balls have
doubled hi volume in the proofer the molder takes them and molds
them into loaves and drops them into pans for the oven.
The automatic wrapping machine along with the other automatic
bakery machinery above mentioned has made it possible for the
baker te guarantee to the public bread which contains no disease
germs.
The richness of bread is directly associated with the fermentation
of the dough. The rich bread flavor is supposed to be due to "split-
protein products" produced during fermentation. The flavor of flour
is a very different thing from the flavor of rich bread. The bread flavor
is something very complex and delicate as shown by the fact that any
small change in manipulation changes the flavor of the bread.
Bread made from dough, not fully fermented, is hard and horny
while bread made from dough over-fermented is crumply. In the
first case the gluten is not sufficiently broken down and in the latter
it is broken down to suoh a point that it no longer holds the bread
constituents together, that is, it has lost its elasticity.
Lactic and acetic bacteria develop in dough from the start of fer-
mentation and play some part in giving bread its flavor. If bread
dough is fermented too long these bacteria produce so much acid
that the bread is sour.
In fermenting straight doughs, four and one-half hours is the
most commonly used fermentation period. As the dough comes from
the mixers its temperature is usually 82 degrees F. in winter and 79
degrees F. to 80 degrees F. in summer. The amount of yeast used is
usually one and one-half per cent. The dough should be about 58
per cent water, and one and three-quarters per cent salt, one and one-
half per cent sugar and one and one-half per cent malt. In addition,
bread generally contains milk or milk powder, and shortening.
144 INDUSTRIAL FERMENTATIONS
During fermentation
the
dough
is
usually given three "punches."
The first comes
at the end of
three hours when
the^
dough
is
high
in
the fermenting trough.
To
determine
the
proper time
to
punch
re-
quires long bating experience.
The
second punch
is 30
minutes later,
and
the
third
is
thirty minutes after
the
second.
Bread Improvers.
The four fundamental constituents
of
bread
are:
flour, water,
salt
and
yeasty
All
bread contains these
and
moat bread contains
one
or more
of a
long list
of
substances known
as
bread improvers.
The
quantity
of
these four fundamental constituents used
by all
bread-
makers
is
about
the
same.
The
manufacture
of
yeast
has
become
so standardized that
the
product
is
uniform, giving
the
same results
from
day to day and
year
to
year.
The
grading
of
flour
is
perfected
to
the
extent that standard brands
of
flour
can be
counted
on to
give
satisfactory results although there
is
some variation which becomes
important when bread
is
made
on a
large scale.
The
water
of
different
localities makes considerable difference
in
bread.
Bread improvers consist
of
substances whioh, added
to the
four
fundamental bread constituents mentioned above, will improve
the
bread. These bread improvers
are
added
to
perfect
the
bread
in one
or more
of the
following ways': color, bloom, size
of loaf,
shape
of
loaf,
grain, texture, velvetiness
of
crumb, taste, flavor, aroma, zest
of
loaf,
length
of
time required
for
staling, economy
of gas
production
in dough,
or
water absorption capacity.
The largest users
of
bread improvers
are the
bakeries where
hun-
dreds
of
thousands
of
loaves
of
bread
are
produced
per day. The use
of certain improvers
in
bread might
not be
found
of any
great value
from
the
standpoint
of
profits
to the
small bakery with
an
output
of
a few
hundred loaves
per day but
when figured
on an
output
of
thousands
of
loaves
per day, the
saving becomes considerable.
The
introduction
of
many bread improvers
has
been
due to the
struggle
to improve
the
loaf
and at the
same time
cut
costs.
Many
of the
bread improvers
are
compounds
or
products whioh
have
an
advantageous effect
on the
yeast
in
bread making. Yeast
attacks
the
Bugars
of
bread
and
converts them into alcohol
and
oarbon
dioxides, thus aerating
the
bread dough. Also
due to the
enzyme, endo-
tryptase made
by
yeast,
it
acts
on the
proteins
of
dough, breaking
them down into simpler compounds^ which
is
spoken
of as the
ripening
of
the
dough. Compounds which stimulate
the
yeast
to
greater enzyme
production
aid in the
ripening
of the
dough. There
are
several such
compounds
on the
market.
Not
only
do
they affect
the
yeast
as to
enzyme production
but as to
speed
of
reproduction
and as to
kinds
of
biologic products created. They have
to do
with
the
flavor
of the
finished bread.
Malt
is
very extensively used
as a
bread improver.
Its
action
in
bread
is
varied
It not
only oontains diastase
but
several proteolytic
BREAD-MAKING
enzymes important
in
bread-making, both from
the
standpoint
of
yeast food
and
gluten splitting.
Some bread improvers
are
made
of
modified starch, some
of
certain
chemicals which stimulate yeast activity,
and
some contain shortening
materials.
Concerning
the use of
flour improvers Wahl
and
Wahl,
in
Bakers'
Helper
say: "The
common interpretation
of the
word 'improver*
in
the
baking industry
is
1
'some substance which, when added
to the
dough will effect
an
improvement, either
in the
economic production
of
the
bread
or in the
bread
itself.' For
instance, improvers
may in-
crease
the
water absorbing power
of a
flour
or
lessen
the
time
of
fermentation,
or
effect
a
saving
in the
amount
of
yeast. Other
im-
provers produce much greater color
of the
crust,
or
whiteness
in the
crumb
or
effect
a
larger volume
per
weight
of
bread,
or may
cause
an improvement
in the
flavor.
"Thus,
it is
convenient
to
classify those various items, which
in-
fluence direotly
the
economic production
of the
bread
and
which
may
be altered
by
added improvers,
and it is
also convenient
to
classify
those properties
of the
bread itself which
may be
effected
by
added
improvers.
The
points
to be
considered
in the
economic production
of bread
are as
follows: 1st—Time
of
dough fermentation; 2nd—
Amount
of
water absorbed; 3rd—Amount
of
yeast required; 4thr-
Amount
of
wheat flour necessary; 5th—Amount
of
fermentation losses.
"Any decrease
in the
time
of
fermentation will effect
the
economio
production
of a
loaf
of
bread inasmuch
as it
lessens
the
amount
of
labor required
and
decreases
the
time
of use of the
various dough
apparatuses, thus allowing
a
larger bread production with
the
same
equipment. Certain substances
may be
added
to the
bread dough
which will ripen
the
gluten
of the
flour
in
less than normal time, thereby
conditioning
the
dough
for the
baking thereof
in a
muoh shorter than
normal time
and
would
in
that case lessen
the
economic production
of
the
bread, giving
the
added substance value accordingly.
"The economic production
of
bread
is
greatly influenced
by the
amount
of
water incorporated into
the
dough,
a
large proportion
of
which
is
retained through
the
baking stage
and
remains
in the
bread,
Bread sold
by
weight will
in
this case
be
much more economically
pre-
pared than
if
less moisture were contained
in the
bread. Several
sub-
stances'
may be
added
to the
dough
to
allow
a
greater addition
of
water, either
by its
influence upon
the
water absorbing oapacity
of
wheat flour
or by the
greater water retaining oapacity
of the
added
substance
iteelf.
"Yeast
not
alone aerates
the
dough through
the
evolution
of
carbonic acid
gas, but it
also excretes
a
substance, termed
by the
biochemist, 'endotryptase,' which acts
on the
glutenous substances
of
the dough
in
such
a
manner
as to
modify
it in the
direction
of
greater
elasticity, that
is, to
'ripen'
it."
It
has
long been known that fermentation cannot
go on
without
more
or
less loss
to the
substance fermented.
146 INDUSTRIAL FERMENTATIONS
Bread-Making Losses.
Kohman says, "In making bread with yeast it is found that best
results are obtained when the dough is allowed to rise from 1 to 4
times depending upon the strength of the flour previous to moulding
into loaves. During this period of fermentation which generally
ranges from 5 to 8 hours in the 'straight dough' process of making
bread, various chemical and physical changes take place which render
the gluten more elastic and better suited for the production of light
bread. These changes are chiefly: (1) The formation of alcohol and
carbon dioxide from the sugars; (2) the production of soluble carbo-
hydrates as sugars and dextrins,i from insoluble forms as starch;
(3) the production of various organic acids such as lactic, acetic, and
at times butyric; (4) a partial solution of the proteid compounds
in the flour: (5) the formation of amid and ammonium compounds
from insoluble proteins; and various' other changes that are only
incompletely understood. Inasmuch as many of the substances formed
during the processes of fermentation are either gases or are volatile,
appreciable losses of dry matter occur during the fermentation, and
baking of bread."
The loss of dry bread substance during bread-making has been
given by different authors as between 1.5 per cent to 11 per cent. As"
a general rule the loss increases the longer the fermentation.
Kohman, Hoffman, Godfrey, Ash, and Blake have studied the
use of certain yeast nutrients in bread making. They say, "One of
the important problems studied in our bread investigations was the
effect of certain mineral salts (such as commonly found in natural
waters) upon the fermentative activity of the yeast in bread-making.
It was found necessary by the Ward Baking Company (who operate
bakeries in several cities) to change the quantity of yeast as well as
the fermentation period of their dough batches in the different cities,
in order to produce a standard product, or nearly so, even though all
the raw materials used were identical (being purchased through a
central office). Upon investigation it was found that variations in the
activity of the yeast were due to the differences in the mineral content
of the waters used for making bread in these cities.
"The carbonates are especially common in natural waters and as
a class are objeotionable in bread, since they neutralize the acids of
the dough and thus
1
interfere with the progress of the fermentation.
More particularly, the carbonates of magnesium and the alkali metals
should be considered as being detrimental to the fermentation of the
yeast."
They say, "Like many other acids, glutamic acid matures or ages
the_
dough and, in addition increases the gas production of the yeast.
This accelerating effect upon the yeast was observed in bread and like-
wise in fermentating cane sugar, dextrose, and malt extract.
"In fermentation of this kind other acids failed to increase the
fermentation as did glutamic acid hydrochloride, so we were led to
BREAD-MAKING 147
believe that it was not a matter of acidity but that the glutamio acid
hydrochloride owes ite accelerating effect to its nitrogen content."
The fate of caloium compounds added to bread dough is explained
by these authors (Kohman, Hoffman, Godfrey, Ash, and Blake) as
reacting with the phosphate of the wheat. They say, "It has been
shown by Teller that the phosphorio aoid in flour exceeds by ten times
the calcium and it may be safely said that even by the use of the new
process, the bread contains several times as much phosphorio acid as
is required to combine with the oaloium. Under these conditions, the
potassium phosphate of the wheat undoubtedly interaots with the
caloium sulphate, as it does in wort in accordance with the following
equations:
+ CaSO* = CaHPO* + KHSO,
SO*
= Ca
8
(POJ
a
+ K
2
SO
4
+ KHSO*
"The increased lime oontent of bread by the use of the new
process is a very happy coincidence even though incidental. Un-
fortunately, in modern methods of milling the greater part of the
mineral constituents of wheat is lost to white flour. As indioated by
Teller seven-eighths of the phosphoric acid, eleven-fourteenths of
the potash and lime of wheat are found in the Btock feed; consequently,
a partial restoration of the lime in white bread must be considered
highly desirable."
Kohman, Hoffman, Godfrey, Ash, and Blake draw the following
conclusions from their work with yeast nutrients in bread-making:
"I.
By the use of minute quantities of ammonium and oalcium salts,
and potassium bromate in bread, from 50 to 65 per cent of the usual
amount of yeast can be saved.
"H Incident to the economy in yeast thus effected, there is a
saving of about 2% fermentable carbohydrates, calculated upon the
total flour UBed, due to the greatly diminished consumption of these
by the yeast.
"III.
The proper
UBO
of nutrient salts for the yeast gives greater
control over the dough batches and aids in the production of better
and more uniform bread regardless of the locality.
"IV. The added salts conserve the inherent qualities of the dough
and consequently maintain its stability and strength to a far greater
degree than by the old process.
"V.
The finished loaves are improved in quality, flavor, texture,
bloom, and uniformity."
Wahl says that bread-making losses are generally due to carbonio
acid gas and to volatile alcohols. He adds, "The more rapid the fer-
mentation phenomenon, and the longer the time, the greater will be
the loss from this cause. Improvers may effect the properties of a
loaf of bread, making it much more readily salable, thus: these proper-
ties may be listed as follows:
"1.
The volume per weight and the shape of bread.
"2.
The color, bloom and softness of crust.
148 INDUSTRIAL FERMENTATIONS
"3.
The color, grain, texture and velvetiness of the crumb.
"4.
The taste, flavor and aroma.
"5.
The zest, palatability and appetizing qualities.
"6.
The wholesomeness and digestibility."
In Bakers' Helper, A. Wahl and R. Wahl say that they have
demonstrated, "That the globuli (gluten) of wheat flour whioh is
insoluble in water, is digested and broken down into a soluble form
during dough ferments. This is accomplished by the activity of pep-
tase in the dough, which is incorporated to a small extent with the
flour
itself,
but more abundantly with the yeast. The peptase which
exists in the interior of the yeast cell is termed 'endotryptase,' and is
excreted by the yeast in order to digest the insoluble protein (gliadin
and ghrtenin) material surrounding the yeast cell to' simple soluble
forms so that they can be absorbed by the yeast as
1
food. The result
of the action of endotryptase of yeast and the peptase of flour is known
to the baker as 'ripening of the dough.' The aotivity of the proteolytic
enzymes (endotryptase and peptase) not alone modifies the gluten in
the direction of greater elasticity (ripening of the dough), but produc-
ing from the peptonization of the globulin (gluten) certain simpler
substances known to the chemist as the albumins
1
and amino bodies.
The latter, nitrogenous substances, are in the best form for yeast
nourishment and consequently act to stimulate and activate the yeast
by affording it increased nutriment which increases the number of
yeast cells and gas evolving power of each cell. The yeast in its en-
livened condition also tends to separate into individual cells and thus
disintegrate the cell aggregations so often formed by bakers' yeast
of to-day. These cell clusters produce irregularity of texture with
oftentimes larger holes. The digestion of the gluten to albumins by
the proteolytic enzymes referred to, aids
1
in forming a flaky texture
since this class of substance coagulates with heat (becomes insoluble
by the heat of the oven). Thus the peptic digestion is beneficial not
alone in that it modifies the gluten in the direction of greater elasticity,
but also produces the albumins, a clasB of proteins' which are so
ohanged by the heat of the oven as to give a flaky texture, thereby
causing a whiter appearance of the crumb (this action is similar to
the change occurring during the boiling of the white of an egg). The
invigoration of the yeast causes the production of a large number of
fermentation gas cells, thereby producing a greater column per weight
of bread, and producing an even, uniform texture.
"Any substance added to the dough containing active peptase will
tend to shortening the time of dough fermentation and to improve
the production of bread or the bread itself in the above directions.
The volume per weight and shape of a loaf of bread depends largely
on the size and number of fermentation gas cells and on the thickness
of the walls of these cells. The quality and quantity of the elastic
material in the bread dough is largely responsible for the conditions
of these cells, and any material added to the dough whioh will modify
the glutenous
1
substances of the dough in the direction of greater
BREAD-MAKING
elasticity, so as to allow the production of a large number of small
thin-walled fermentation gas cells will cause an improvement in the
volume and shape of the bread. The number and size of the fermenta-
tion gas cells is also largely dependent on the number and activity of
the individual yeast cell groups existing in the dough and any principle
which tends to increase the distribution of the invigorated and aotivated
yeast as
1
to make it separate into individual cells or very small clusters
would effect a similar improvement in the bread.
"The color and bloom of the crust is dependent largely upon the
amount and kind of oaramelizable sugars existing in the bread dough
at the time of baking. Wheat flours contain very little natural sugar
of this kind and various substances containing this principle may be
adde.d to bread doughs which will give a deeper color to the crust of
the resulting bread than would be obtainable by the use of cane
sugar alone.
"The color of the crumb of a loaf of bread is influenced largely
by the way light strikes the texture and upon the physical condition
of the starch and nitrogenous material after baking. During the
baking of the dough, the soluble albumins coagulate into white flaky
masses. Certain substances added to bread dough either act in such
a manner as to render the starch and nitrogenous material white in
appearance or effect the production, of a comparatively large amount
of albumins' in the dough."
Bread Diseases.
"Sticky" or "Slimy bread" is a bread disease which often occurs"
during hot weather. After eight or ten hours the bread affected
gradually becomes slimy, until at the end of two or three days it
After
EimUr.
Fia.
21J—Potato
bacillus oaumng "rope" in bread.
may be pulled into strings. The bread takes on a faint sickly odor)
and finally brown spots appear. This disease is due to bacterial*
growth. Vogel in Germany found "ropy" bread to be due to the
growth of potato bacilli, B. panis viscosuer I and B. panis viscosus II.
Watkins in the Journal of the Society of Chemical Industry, 1906,
says that in bread held at 18 degrees C. ropiness did not occur but in
150 INDUSTRIAL FERMENTATIONS
bread at 25 to 30 degrees C, ropiness developed readily. He found
that .1% acetic acid prevented ropiness in bread and that lactic
acid had the same effect. The organisms stood boiling for 30 minutes
on three conefecutive days. He found these organisms often on
wheat and in flour.
Experiments at Wisconsin Experiment Station (Wisconsin Re-
port 1898, page 110) showed that the bacillus entered the bread
with the yeast. It also was shown that the bacillus could survive
the heat of baking.
RnmTnp.rH.in Bakers? Weekly gives the following method of con-
trol of rope in the bakery:
"The best method of procedure is to use up all raw materials on
hand. These are very likely to be contaminated- To prevent the
development of rope in bread made from the ingredients in stock a
small quantity of some organio acid should be added to the doughs.
Both lactic acid, the acid of sour milk or buttermilk, and acetic
acid, the acid of vinegar, are found to be satisfactory. Acetic acid
seems to be somewhat more active in suppressing the trouble but
its flavor is undesirable in bread. Lactic acid, on the other hand, is
odorless and does not produce so disastrous an effect upon the gluten.
It is found neoessary to use more lactic acid than acetic acid to produce
the Bame effect. While these acids do not kill the organism, still
they prevent its growth.
"One should not use more than 0.3% or one-third pint, of acetic
acid per 100 lbs. of flour, or 0.5% or one-half pint of lactic acid
per 100 lbs. flour. Greater amounts will disintegrate the gluten,
weaken the dough and a loaf of small volume will result.
"In order to entirely eliminate the rope bacteria one should
fumigate the shop with formaldehyde candles, or spray the floor,
walls,
ceiling and all pieces of machinery with a 10% solution of
formaldehyde.
"If fumigation is practiced all walls and floors should be first
wet down with Water and all cracks tightly sealed. The rooms
should be left closed from six to twelve hours after fumigation.
"In open air shops, snoh as are found in army baking, rope has
been checked by using a piece of old dough in each newly made
dough. This old dough will contain enough lactic and acetic acids
to prevent the development of the rope bacteria in the finished
loaf."
Chromogenic Breads.
Micrococcus prodigiosus sometimes causes blood red stains in
bread; however this bread trouble does not occur very often. Other
chromogenio organisms give bread other colors.
Sour Bread.
During fermentation bread dough sometimes becomes abnormally
sour due to the excessive growth of lactic and butyrio acid bacteria.