VOL. LXV
INDIANAPOLIS, JUNE 4, 1910.
NO. 23
Written for the Indiana Farmer:
THE CHEMISTRY OP BREAD.
By  J.   N.   Hurty,   M.   D.,   State   Health
Commissioner.
In marble, chalk and many other
mineral substances, we find wrapped in
strong chemical combination an interesting and most important compound
gas. It is known to the chemist as
carbon dioxide, but Is frequently termed carbonic acid gas. It plays a mighty
part in the animal and vegetable, as
well as in the stones. Two elements
compose it. The solid carbon, (charcoal) and that king of elements oxygen,
unite in the proportion of one of the
first to two of the last to form its molecule. It is colorless, but has a pungent
taste and smell. Inhaled it acts as a
narcotic poison, but when swallowe 1
is harmless, being even grateful to the
stomach. Our breads and cakes, an.l
pastry, owe their porousness,—that is
lightness,—and much of their digestibility to this gas. Yeast is added to
dough that it may through its life process give off carbon dioxide, to the end
that the loaf may be filled with cells
and so made light.
In brisad maiclng we have to deal
mostly with starch, which is associated
With gluten, and a little fat, sugar, salts
and fibre; for these compose wheat
flour. Starch makes up 66 to 75 per
cent of the whole, while the gluten-pro-
teids is a better chemical name—exists
to the extent from 9 to 15 per cent, the
remainder being water 12 to 14 per
cent, fat 0.8 to 1.6 per cent, and mineral matter in about equal proportions
0.7 to 1.6 per cent. When properly
wetted and worked flour forms a plastic dough. The gluten is the sticky element, the one that causes the other
ingredients to form into a mass. If
we bake this unleavened dough, the
same chemical changes will occur that
attend the usual baking of bread, but
the physical results are widely different. The unleavened bread is somewhat unpalatable and not easy of digestion, while the leavened baked loaf
is most toothsome and quickly digested.
These differences are not chemical, but
physical; yet a chemical knowledge of
the ingredients of flour leads us to an
understanding of the situation. Let
us return then to a chemical consideration of stareh and gluten.
The last named is a nitrogenous body
present in nearly all cereals. It may
be obtained by washing flour ln a muslin bag. The starch is removed bj the
running water, and the gluten remains
behind in the bag. This crude substance is a mixture of three or four
distinct bodies, to which the following
names have been given:
(a) Gluten casein
(b) Gluten fibrin
(c) Muceiden
(d) Glaiden
It is very tenacious and sticky and may
be drawn out into strings. It is this
property which renders it so valuable
in bread making. Five elements enter
into its composition; they are:
Carbon, 52.8 per cent
Hydrogen, 6.9 per cent
Nitrogen,  16.8  per cent
Oxyge , 21.7 per cent
Sulphur, 1.8 per cent.
Gluten is insoluble in water, but may
be eonverted into a soluble form known
as peptone by the action of pepsin and
certain other ferments.
The chief nutritive function of the
proteids, to which class gluten belongs,
is to build up the wasting nitrogenous
tissues. If proteids are withdrawn
from the diet the animal dies of nitrogen starvation.
Starch is found in the form of small
bodies, called "starchgrains," which are
stored up in various parts of plants.
They vary exceedingly as to shape and
size according to the plant from which
they are taken. Under the microscope
they appear to be made up of a number
of layers, surrounding a nucles termed
the hilum.
The starch granule has an interesting structure. It appears from chemical analysis to consist of two distinct
From the composition of wheat,
when compared with the composition
and nutritive needs of the human body,
it is a plain conclusion that the whole
wheat berry is a typical food. AU of
our high .grade flours, en account of the
refined methods of manufacture, are
not true representatives of the food
value of wheat. They exclude the bran
in great part, and as therein lies the
phosphates and other salts, much of
the life of the food is lost.
The germ of the wheat is also thrown
out in "fine flours," and thus is lost the
fat, but this is not of so great moment
as the loss of the phosphates, for we
have learned to put into the loaf lard
or milk, and our bread is spread with
butter, and so the needed fat Is restor-
Farm Home of W. O. Ballard, Crawford County.
bodies, the inner one being the true
starch, which is surrounded by an envelope, termed Amylocellulose. Starch
is composed of the three elements, carbon, oxygen and hydrogen, but it differs
very much from the fat, inasmuch as it
contains a smaller percentage of carbon, and the hydrogen and oxygen always exist in the proportion to form
water. It belongs to the class known
as "carbo-hydrates," in which class
sugar also is placed.
Acted upon by heat, starch is changed into dextrin which, unlike the former, is soluble in water and has a faintly sweet and gluey taste. In boiling
water the starch granule bursts, and its
structural condition is wholly destroyed, while part becomes soluble. Starch
is quickly and easily converted into glucose by boiling in dilute hydrochloric or
sulphuric acid, and starch paste may
be instantly turned into maltose (a
form of glucose) by malt liquor, or by
ptylin the amylolytic ferment of the
saliva.
The fat in wheat resides almost entirely in the germ, and as the germ is
rejected in the milling process for fine
flour, this grade therefore carries the
minimum of fat. In whole-wheat
flour, the fat is all retained.
The flour fat plays no part in the
chemistry proper of bread, but gives
richness and flavor. It is a neutral
body during fermentation, and is not
materially changed by the baking, but
like the fibre and mineral matter, has
important dietary considerations.
The mineral matter found in wheat
flour is principally phosphates of potassium and magnesium. The phosphates of sodium and calcium are
found in the ash to the extent of 5 to
6 per cent, while oxide of iron and
silica make up the remainder.
ed.
Given flour, the basis and great ingredient of bread, and of the chemical
composition now understood, we may
proceed to make our loaf.
The first step is the making of the
ferment. This consists of potatoes,
boiled and mashed with water into a
moderately thin liquor. To this is added yeast and the fermentation allowed
to proceed for some time before the
next step is taken. The sponge is next
made by mixing flour with the ferment
until a slack dough is produced. A
second fermentation goes on, and when
it commences to subside more flour is
added to make the dough. The dough
is kneaded in order to thoroughly mix
in the air, and thus give additional
lightness and a whiter loaf. Baking, of
course, finishes the process.
Yeast is a plant, the products of its
growth in dough being carbon dioxide,
alcohol, and a little glycerin. Saccinie
acid is also formed in small amount.
After the true yeast botanical name,
Saccharomyces Cerevisiae, has done its
work, other yeasts or plants may grow,
and then other products are formed, as
lactic and lacetic acids, which make the
1 read sour.
The baker's skill is shown in so conducting the fermentation as to prevent
ali other kinds of fermentation, save
the alcoholic.
The chemical action of yeast transforms both the starch and the gluten
in part. It seizes upon some of the
cooked starch, changes lt Into sugar,
and then breathing lt In, exhales the
gas which mixes with the doughy mass
"raising lt" and giving the necessary
lightness.
The process is silent and marvelous,
and our wonder is excited by a con-
temt'ation  of  the  fact  that,  a  micro-
ortjarism so small that high powers of
the microscope are required to disclose
it to us, performs a work so necessary
for our existence. The yeast feeds
somewhat upon the gluten, transforming the little it uses into many pleasantly flavored but complex compounds;
and the gas penetrating the remaining
gluten makes it porous and digestible.
The phosphates too, have added to tha
strength and life of the yeast, but they
still remain as phosphates. The total
result of the fermentation then appears
to be—slight chemical changes in the
gluten, a considerable chemical change
in the starch, and a pronounced physical change in the dough.
In the oven, the heat brings about
further chemical changes of a most
complex nature. The heat kills the
yeast and the fermentation isjstopped,
the starch grains are burst, the gluten
develops delicious flavors, much of it
becomes soluble and all is made into digestible substances.
In the crust resides much that is best
in the loaf of bread. The change of
starch into dextrin takes place mainly
in the crust, and in it is also developed
most toothsome flavors, and its digestion is very easy.
"White bread and graham bread, o.
bread from whole wheat flour, have
been much discussed, but the subject
has not been exhausted. It has been
shown that white bread alone is in-
capablaof supporting a healthy life,and
is not strong among the foods which
are richest in mineral matter. Those
who partake of white bread should
take care to supplement It largely with
other foods, in order to make up for
the lack of lime. If they do this, no
ill results are likely to follow; but it is
distinctly injurious to the body if it
forms *he staple food, and is not supplemented by other foods richer in
lime. On no account should it enter
largely into the diet of children, unless
other foods are added, such as milk and
meats, or meat juices, rich in lime and
phosphates, for the young require especially calcium phosphate to form
their bones and teeth, and to promote
the growth of new tissues. Many hy-
gienists unequivocally condemn the use
of white bread, but when it only forms
a small part of the diet, and if the individual partakes moderately of fresh
meat, or other foods which are rich in
salts, the use of white bread is not detrimental to a vigorous life, and eaters
of white bread need not alarm themselves about a deficiency of phosphates
so long as they have a variety in their
diet. With those, however, who live almost entirely upon bread the case Is
very different. It is known that the
children of the very poor are raised
very largely upon a poorly made white
bread and a cheap unwholesome molasses. With tissues and bones imperfectly constructed from white bread,
these children grow into manhood, and
as a consequence are lazy and shiftless,
and then it ls In order for those who
enjoy a superabundance to defend
themselves in the accident of their
possessions and greater strength, by
pointing out and condemning this laziness. The preference of the poor for
the poorest grades of bakers' white
bread, is accounted for when we know
that the inferior loaves are larger in
appearance, although they weigh the
same as the better bread.
At the groceries, we find many differ-