Studies on the digestibility and nutritive value of bread at the University of Minnesota in 1900-1902

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Title:
Studies on the digestibility and nutritive value of bread at the University of Minnesota in 1900-1902
Series Title:
Bulletin / U.S. Department of Agriculture, Office of Experiment Stations ;
Physical Description:
52 p., 3 leaves of plates : ill. ; 23 cm.
Language:
English
Creator:
Snyder, Harry, 1867-1927
University of Minnesota
Publisher:
G.P.O.
Place of Publication:
Washington
Publication Date:

Subjects

Subjects / Keywords:
Bread   ( lcsh )
Genre:
federal government publication   ( marcgt )
non-fiction   ( marcgt )

Notes

Bibliography:
Includes bibliographical references.
Statement of Responsibility:
by Harry Snyder.

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Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 022023965
oclc - 09667132
lccn - agr09002662
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AA00014536:00001


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HARRY SNYDER, B. S.,
Professor of Chemistry, Cllege of Agriculture, University of Minnesota, and
Chemist, Agricultural Experiment Station.


WASHINGTON:
GOVERNMENT PRINTING OFFICE.
1903.


U. S. DEPARTMENT OF AGRICULTURE.

mOFl OF IXP.RIMENT STATIONS-BULLETIN NO. 126.
A. C. TRUE, Director.






STUDIES ON THE DIGESTIBILITY AND

NUTRITIVE VALUE OF BREAD


AT



THE UNIVERSITY OF MINNESOTA


IN



1900-1902.


BY


I.


































OFFICE OF EXPERIMENT STATIONS.

A. C. TRUE, Ph. D., Director.
E. W. ALLEN, Ph. D., Assistant Director and Editor of Experiment Sation Record.
C. F. LANGWORTHY, Ph. D., Editor and Expert on Foods and Animal Production.

NUTRITION INVESTIGATIONS.

W. O. ATWATER, Ph. D., Chief of Nutrition Investigations, Middletown, Cnn.
C. D. WOODS, B. S., Special Agent at Orono, Me.
F. G. BENEDICr, Ph. D., Physiological Chemist, Middletoun, Conn.
R. D. MILNER, Ph. B., Editorial Assistant, Middletown, Conn.
2




























".I














LETTER OF TRANSMITTAL.


U. S. DEPARTMENT OF AGRICULTURE,
OFFICE OF EXPERIMENT STATIONS,
Washington, D. C., February 15, 1903.
SIR: I have the honor to transmit herewith, and to recommend for
publication as a bulletin of this Office, a report of investigations on
the digestibility and nutritive value of bread carried on at the Uni-
versity of Minnesota in 1900-1902 by Harry Snyder, professor of
chemistry in the State university and chemist of the agricultural
experiment station. The studies were conducted under the imme-
diate supervision of Prof. W. O. Atwater, chief of nutrition investi-
gations, and Prof. Charles D. Woods, and form a part of the investi-
gations on food of man conducted under the auspices of this Office.
Thanks are due the Northwestern Consolidated Milling Company, of
Minneapolis, Minn., for specially grinding samples of hard wheat,
and to the Goshen Milling Company, of Goshen, Ind., and the Christian
Breisch Milling Company, of North Lansing, Mich., for similar favors
with respect to soft wheat.
The results of these investigations are in accord with those obtained
in former studies, and indicate that fine patent flours from both hard
and soft wheat are more digestible than corresponding coarse flours,
though they contain somewhat less protein and mineral matter pound
for pound. The investigations also show that all flours are quite
thoroughly digested, and furnish experimental proof of the generally
recognized fact that wheat flours of all grades are among the most
important articles of diet.
Respectfully, A. C. TRUE,
Director.
Hon. JAMES WILSON,
Secretary of Agriculture.



































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e '
















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CONTENTS.


Introduction....----..----.................---.....-.......------....------------
Methods of sampling and analysis..--..---............----.--..------....----
Description of samples of food materials. .............................-----
Composition of samples of food materials................. ..-----------...--------
Composition of feces and urine obtained in digestion experiments.........------..
Experimental methods ..........-....---.....--------..... ---...---------
Details of the digestion experiments with bread from different grades of hard
spring wheat flour...............--.................. ------.............
Digestion experiment No. 242. .....................-.........-----.....
Digestion experiment No. 243.........................................
Digestion experiment No. 244 ............................... ........--
Digestion experiment No. 245......................................---------
Digestion experiment No. 246..........-..........................----
Digestion experiment No. 247.......................-...............
Digestion experiment No. 248 ..........-.......- .....................
Digestion experiment No. 249............--...............--......-...
Digestion experiment No. 250-........................................
Summary of results obtained with hard spring wheat products...........
Details of the digestion experiments with bread from different grades of soft
winter wheat flour....................................................
Digestion experiment No. 309...-................-...-.................


Digestion experiment
Digestion experiment
Digestion experiment
Digestion experiment
Digestion experiment
Digestion experiment
Digestion experiment
Digestion experiment
Digestion experiment
Digestion experiment
Digestion experiment
Digestion experiment
Digestion experiment


Page.
7
8
10
12
17
18


No. 310..........................................
No.311.......-......-...........................
No.312..........................................
No. 313 ........ .................... ..............
No.314..........................................
No.315 .................... ......... ............
No. 316 ................................ .........
No.317..........................................
No. 318............................. ............
No.319 ......... ................................
No.320..........................................
No. 321 ..........................................
No.322..........................................


Digestion experiment No. 323 .....-..................................
Summary of results obtained with soft winter wheat products....-...-...
General summary of results and conclusions -................-.............
5





I1:


ILLUSTRATIONS.


PLATE I. Fig. 1.-Flour particles from straight patent flour No. 240. Fig. 2.-
Flour particles from entire-wheat flour No. 241..................
II. Fig. 1.-Flour particles from graham flour No. 243. Fig. 2.-Feces
from bread from straight patent flour ....................---....
III. Fig. 1.-Feces from bread made from graham flour. Fig. 2.-Feces
from bread made from entire-wheat flour ----.-----------------
6


48

48
481


.X
*. I


S "m















STUDIES ON THE DIGESTIBILITY AND NUTRITIVE
VALUE OF BREAD.


INTRODUCTION.

The investigations reported in this bulletin, which were carried on at
the University of Minnesota in 1900-1902, are a continuation of the
experiments on the digestibility and comparative nutritive value of
bread made from different grades of flour reported in previous bulle-
tins of this Office,a and include two series of digestion and nitrogen
metabolism experiments with healthy men on a diet of milk and bread
made from different grades of wheat flour, namely, straight patent,
entire wheat, and graham. In the first series, which included 9
experiments carried on in 1900-1901 (pp. 20-31), the different grades of
flour used were all ground from the same lot of hard Scotch Fife spring
wheat. In the second series, which included 15 experiments, carried
on in 1901-2 (pp. 32-50), the flours were ground from soft winter wheat.
The standard grades of flour produced by the modern process of
milling are discussed in detail in a former bulletin6 and also in later
pages of this bulletin. Briefly stated, by graham flour is meant the
product obtained by grinding the entire wheat kernel. Entire-wheat
flour is the product obtained by removing about one-half of the coarse
bran before grinding. This flour is finer than graham, but not as fine
as the patent grades of flour. In milling the patent flour all of the
bran is removed. Several grades of patent flour are produced, but
the one most commonly found on the market, known as "standard
patent," "straight patent," or "straight grade" consists of the first
and second patent and first clear grades combined. By ordinary proc-
esses of milling a little over 72 per cent of the total wheat is recovered
as straight or standard patent flour and about 2.5 per cent as low grade
and red dog" flours, the remaining 25 per cent being returned in the
form of bran, shorts, and other offal.
During late years the relative food valwe and merits of these differ-
ent kinds of flour have been the subject of extensive discussion; but
an examination of the literature on bread and flour shows that but few
digestion experiments which are really directly comparable have been
aU. S. Dept. Agr., Office of Experiment Stations Buls. 67 and 101.
bU. S. Dept. Agr., Office of Experiment Stations Bul. 101, pp. 7,8.
7
C:









made with the different kinds of flour. Wheat ranges in protein con-
tent from about 11 to 17 per cent; therefore, in order that the results of
experiments may be comparable, the three kinds of flour should be
milled from the same lot of wheat. In the former report it was shown
that when the three different kinds of flour were ground from the same
lot of hard spring wheat the graham and entire-wheat flours contained
a little more protein and gave a slightly higher fuel value than the
straight patent flour; but the coarser graham and entire-wheat flours
had a lower coefficient of digestibility than the finer straight patent
flour. Hence the straight patent flour furnished the body more
nutritive material per gram or per pound than either the graham or
entire-wheat flour. Because of the importance of the subject and the
extensive use of wheat as a human food it was deemed desirable to
repeat the work, and in so doing to extend the periods of the digestion
experiments over a longer time than in the case of the experiments
previously reported, in which they were only two days each. The
experiments of 1900-1901 were therefore practically a repetition of
those of 1899-1900, except that the digestion period in each case was
twice as long, i. e., four days.
In 1901-2 experiments were made similar to those of 1900-1901, but
with soft winter wheat, which is somewhat different in character from
the hard spring wheat, in order to determine whether the results would
be the same with flours ground from different sorts of wheat.
In connection with both series of experiments a number of analyses
were made of the varieties of wheat studied and of their milling products
as well as of the milk which formed a part of the diet in the digestion
experiments. The necessary analyses were also made of the feces and
urine to secure data for use in computing the.digestibility of the food"'
and the balance of income and outgo of nitrogen.

METHODS OF SAMPLING AND ANALYSIS.
The analytical methods employed in these investigations were prac-
tically those recommended by the Association of Official Agricultural
Chemists,a a few modifications suggested by experience being intro-
duced.
A sample of each loaf of bread used during the separate digestion
experiments was analyzed. One hundred grams of bread was reserved
for the dry matter determination, and proportional parts of the dry
matter of the bread from various loaves were united to form a com-
posite sample, which contained a part of each loaf of bread propor-
tioned to the size and moisture content of the loaf.
A composite sample was made of the milk in the experiments of
1900-1901 by saving, in a bottle containing 100 milligrams of potas-
a U. S. Dept. Agr., Division of Chemistry Bul. 46, revised.



.... il








S' sium bichromate, 25 cubic centimeters of the milk used at each meal.
SIn the experiments of 1901-2 the amount of milk reserved at each
meal was 50 cubic centimeters. The temperature of the drying oven
was kept at.about 600 C. in all cases of the determination of moisture
in the feces. The bread was also dried at this temperature. Nitrogen
was determined by the ordinary Kjeldahl process. In the case of
wheat and its milling products and bread, protein was obtained by
multiplying nitrogen by the factor 5.7. In the case of protein in the
milk and the feces the factor used was 6.25. No attempt was made to
separate and determine the amount of metabolic nitrogen of the feces.
Carefully purified ether was used for determining ether extract in
the bread and feces. The results obtained for the fat in the feces
were not satisfactory in many cases, although the determinations were
made in duplicate by the method generally followed and considered
reliable. The fat in the milk was determined by the Adams gravi-
metric method. The ash was determined by combustion at a low tem-
perature. The carbohydrates were estimated by subtracting the sum
of the protein, ether extract, water, and ash from 100.
The determination of the ether extract in the feces necessarily
involves an error, owing to the metabolic products present. Another
source of error is in the protein determination. While the determi-
nation of the total nitrogen is satisfactory, the factor for converting
this nitrogen into protein is not perfectly reliable, and in many cases
is very unsatisfactory. It is well known that not all of the nitrogen
of a food is in the form of proteid compounds. In the case of the
food materials used in these experiments, namely, bread and milk,
over 97 per cent of the total nitrogen is in the form of proteids, and
the error from nonproteid nitrogen in the food is therefore small. In
the case of the feces, however, the kinds, proportions, and composi-
tion of the nitrogenous ingredients are not well understood, and the
estimate of protein is at best very crude. The errors involved in
the determination of carbohydrates, by difference, are too well known
to require discussion. Notwithstanding these imperfections of analyt-
ical methods, which are not peculiar to these investigations but are
common to all similar experiments, the results obtained in determining
moisture, ash, total nitrogen, and heat of combustion are believed to
be reasonably accurate, and the deductions drawn from them are
.regarded as reliable.
The calorific value or heat of combustion of the various samples of
food, feces, and urine was determined in the usual way by means of
the bomb calorimeter. In the case of the milk and urine, weighed
blocks of cellulose were employed to absorb the liquid. The absorp-
tion block was saturated, carefully dried, weighed, and again satu-
rated with a weighed quantity of material. After drying at a tem-
perature of 650 C. the block was burned in the calorimeter in the







10


usual way, a correction being made in the results for the heat of com-
bustion of the block employed.

DESCRIPTION OF SAMPLES OF FOOD MATERIALS.

In the milling of the hard spring wheat great care was taken to
secure representative samples. As in the former work, the milling
was carried on under the supervision of Mr. C. E. Foster, of Minne-
apolis, in one of the large flouring mills of that city. Two hundred
pounds each of the three different kinds of flour were obtained from
the mill. As soon as the samples were received at the laboratory
smaller samples were drawn for analysis.
For the experiments with soft winter wheat difficulty was experi-
enced in securing samples of soft-wheat flours that were comparable
with the grades of flour used in former work with hard spring wheat.
The samples of hard wheat used in 1899-1901 were exhaustively
milled and very little flour was left in the bran and middlings.
The samples of soft wheat used in 1901-2 were, as is the custom with
such wheats, less exhaustively milled and more flour was left in the
offals. For this work sets of samples were obtained from two differ-
ent milling companies, and in each case the different grades of flour
were from a single lot of wheat.
A description of the different sorts of wheat used in the experiments,
and of the different grades of flour and milling products made from
them, is here given. These are the samples the analyses of which are
reported in Table 1.
In addition to the various milling products mentioned, which are
standard grades, other grades may be obtained by subdividing a grade
or by mixing or blending two or more grades. Many of the flours
which are placed upon the market are mixtures of two or more stand-
ard grades of flour.
No. 153. Hard Scotch Fife spring wheat, weighing 60 pounds per bushel; screened
but not scoured. This wheat is representative of the hard spring wheat grown in the
Northwestern wheat regions of the United States.
No. 154. Entire-wheat flour from hard spring wheat No. 153. This is the product
obtained by removing a portion of the bran and grinding the remainder of the grain.
It includes the germ and other parts of the offal products which are'excluded from
the patent grades of flour. This flour is coarser in texture and darker in color than
the patent and clear grades. The presence of fine bran particles prevents perfect
granulation. Such "entire-wheat" flour is sometimes called "pulverized graham"
or natural flour."
No. 155. Graham flour from hard spring wheat No. 153. This consists of the
entire wheat kernel including bran, germ, and offal, ground into meal. Graham flour
is practically wheat meal; no sieves or bolting cloths are employed in its manufacture,
and coarse particles of bran, etc., may be observed in the flour.
No. 156. Straight patent flour from hard spring wheat Nc. 153. This includes the
first and second patent grades and the first clear or bakers' grade of flour described
below. Ordinarily about 72 per cent of the screened wheat is recovered as straight
patent flour.







11

No. 157. First patent flour from hanl spring wheat No. 153. This is the highest
grade of patent flour manufactured. Ordinarily about 56 per cent of the screened
wheat is recovered as first patent flour, provided no straight flour is made. All of
the patent grades of flour include the middlings which, by the former processes of
milling, were not reduced to flour but were included in the offal products. The
presence of the granular middlings gives a relatively high protein content to the
patent grades of flour.
No. 158. Second patent flour from hard spring wheat No. 153. This is similar to first
patent, but the bread made from it is a little darker in color and the gluten does not
possess quite so high a power of expansion. The division of the flour into first, second,
and straight patent grades is based entirely upon mechanical processes. In the higher
grades of patent flour the gluten is distinctly different from that in the lower grades.
The higher the grade of flour, the greater the power of expansion. It is this quality
which enables the flour to absorb a large amount of water and as a result produce a
large-sized loaf, and one of good physical properties.
No. 159. First clear flour from hard spring wheat No. 153. After the first and second
grades of patent flour are removed in milling about 12 per cent of first clear grade
is obtained. This grade has a high protein content, but the gluten is different in
character from that of the first and second patent grades of flour. As already
explained, when the first and second patent grades and the first clear grade are
blended as one product, the blend is called straight or standard patent flour.
No. 160. Second clear or low-grade flour from hard spring wheat No. 153. After the
removal of the first and second patent flours and the first clear flour about 5 per cent
of the original wheat can be obtained as second clear or low-grade flour. This flour
is much darker in color than the patent and first clear flours. It contains gluten,
with a low power of expansion, and therefore is not so valuable for bread making as
the higher grades of flour. Second clear flour is characterized by a high protein
content, but for bread making this protein possesses poor physical properties.
No. 161. Red-dog flour from hard spring wheat. This is the lowest grade of flour
manufactured. It is sometimes used for feeding animals, and occasionally for human
food. It is obtained largely from the parts adjacent to the germ or embryo, and is
characterized by a high protein content, this protein, however, having different
properties from that in the higher grades of flour. It possesses but little power of
expansion, and the bread made from this grade of flour is dark in color and poor in
quality, at least as regards its physical properties. In the process of milling the
wheat germ is not included in the higher grades of flour, because its protein is not
composed of gliadin and glutenin. Furthermore, the germ ferments readily, and
thus when present in flour has a tendency to render it unsound. Ordinarily from 5
to 8 per cent of the screened wheat is excluded as germ. This is utilized for the
preparation of breakfast foods, for blending with other cereal food products, and for
other purposes. Frequently, however, the wheat germ finds its way into the shorts
and is used for cattle feed.
No. 162. Wheat shorts or middlings from hard spring wheat No. 153. About 11.5
to 12 per cent of the cleaned wheat is recovered as shorts, which consist of the fine
bran that has been more or less completely pulverized. When the wheat germ is
recovered with the shorts, the product is known as middlings. Such middlingss"
must not be confused with the middlings obtained when wheat is milled by the old
process. As previously stated, the material termed middlings in the old process is
now reduced and recovered in the various grades of patent flour.
No. 163. Bran from hard spring wheat No. 153. This consists of the coarsely ground
episperm or outer covering of the wheat kernel. Ordinarily from 13 to 15 per cent
of the cleaned wheat is recovered as bran.








12

No. 164. Entire-wheat bread. This was made of the flour from which sample No.
154 was taken.
No. 182. Graham bread. This was made of the flour from which sample No. 155
was taken.
Nos. 199 and 217. Straight patent flour bread. In making this bread flour was
used from which sample No. 156 was taken.
Nos. 165, 181, 198, and 216. Milk. Mixed milk, used in the digestion experiments.
No. 218. Cleaned soft winter wheat, from Goshen, Ind., prepared for milling, of
good quality, and weighing 60 pounds per bushel. The sample analyzed was ground
in the laboratory in a Maercker mill.
No. 221. Mixed-grade flour, ground from soft winter wheat No. 218, and consisting
largely of straight flour with some lower grades and a little germ. As already
explained, with exhaustive milling about 72 per cent of the screened wheat is recov-
ered as straight flour, the grade most extensively used for bread making. If a lower
percentage of wheat is recovered as flour, the sample is ranked, commercially, as a
higher grade of patent flour because of its lighter color and other characteristic phys-
ical properties. This sample, No. 221, was not strictly a straight grade flour, but
was more properly a blend.
No. 222. Entire-wheat flour, ground from soft winter wheat No. 218, after remov-
ing a small amount of bran. This sample was different from the entire wheat used
in former work with hard wheat; it had more of the characteristics of graham. It
was, however, more finely pulverized than the graham flours used in the experi-
ments made in 1899-1901.
No. 267. Middlings obtained in the milling of the straight-grade flour No. 221,
from soft winter wheat No. 218. Middlings include the fine particles of bran and
germ, and, in case the wheat is not exhaustively milled, a small amount of the low-
est grades of flour.
No. 268. Bran, from soft winter wheat No. 218.
No. 237. Soft winter wheat, of good quality, from North Lansing, Mich., weighing
59 pounds per bushel, cleaned and prepared for milling.
No. 240. Straight grade or standard patent flour, milled from soft wheat No. 237.
From the analysis of the flour and the appearance of the offals, it would seem that
this flour contained somewhat less than 72 per cent of the original wheat. It should
be classed as a high grade rather than as a straight-grade flour. It possessed good
bread-making qualities, but required more thorough mixing and kneading than
hard-wheat flours.
No. 238. Middlings, from soft winter wheat No. 237, obtained in milling flour No. 240.
No. 239. Bran, from soft winter wheat No. 237, obtained in milling flour No. 240.
No. 241. Entire-wheat flour, prepared from soft winter wheat No. 237.
No. 242. Graham flour, obtained from soft winter wheat No. 237.
No. 223. Mixed-grade flour bread. This was made of the flour from which sample
No. 221 was taken.
No. 231. Entire-wheat flour bread. This was made of the flour from which sample
No. 219 was taken.
No. 244. Straight patent flour bread. In making this bread flour was used from
which sample No. 240 was taken.
No. 251. Entire-wheat flour bread. This bread was made of the flour from which
sample No. 241 was taken.
No. 260. Graham-flour bread. The graham flour used was the lot from which
sample No. 242 was taken.

COMPOSITION OF SAMPLES OF FOOD MATERIALS.

In Table 1, which follows, are given the results of the analyses of
the wheat samples, of the flours and other products made from the
::









13


wheat, of the bread made from the flours, and of the milk consumed
in the digestion experiments.

TABLE 1.-Composition of wheat, fouru, and offal4 and of bread, and milk used in diges-
tion experiments with hard and soft wheat breads.


Whence obtained.


Hard wheat:
Wheat.....................
Entire-wheat flour .........
Graham flour..............
Straight patent flour .......
First patent flour.........
Second patent flour.......
First clear flour...........
Second clear flour.........
Red dog flour.............
Middlings..............
Bran ......................
Bread made from-
Entire-wheat flour......
Graham flour.........
Straight patent flour...
Do.................
Soft wheat:
Wheat from Indiana......
Entire-wheat flour.........
Mixed grade flour.........
Wheat from Michigan......
Middlings................
Bran.........................
Straight patent flour ......
Entire-wheat flour ........
Graham flour...............
Middlings..................
Bran......................
Bread made from-
Mixed grade flour......
Entire-wheat flour.....
Straight patent flour..
Entire-wheat flour......
Graham flour..........
Milk, composite sample.........
.....do .......................
.....do.. ....................
.....do......................
.....do.......................
.....do.........................
.....do......................
.....do.......................
.....do.... ...................


Sample
No.


Protein.a Fat.


Water.



Per cent.
10.41
13.51
13.21
12.38
12.16
12.09
11.92
10.40
10.26
10.17
11.47
40.97
42.68
38.77
37.37
8.09
9.60
10.30
10.25
7.86
8.74
10.97
11.01
11.23
9.76
10.94
39.56
39.50
36.87
37.62
38.12
87.81
87.27
87.59
87.14
87.00
86.56
87.34
87.67
86.50


Per cent.
15.50
13.72
14.21
13.60
13.31
13.05
17.73
20.00
21.83
18.64
17.10
9.32
9.54
9.63
9.74
13.16
12.80
12.30
12.34
17.91
14.96
10.92
12.01
12.24
18.34
16.72
8.01
8.53
7.59
8,33
8.36
3.25
3.13
3.04
3.38
3.31
3.32
2.99
3.00
3.25


Per cent.
2.28
1.69
2.01
1.30
1.21
1.37
1.98
3.17
6.10
6.04
4.23
.19
.29
.04
.26
1.52
1.54
.93
1.35
5.18
4.41
.50
1.53
1.41
4.65
4.42

.60
1.02
.38
1.08
.87
3.80
4.00
3.82
4.15
4.38
4.67
4.09
3.85
4.45


Carbo-
hydrates.



Per cciil.
69.88
70.10
68.56
72.04
72.93
73.03
67.37
64.24
57.72
50.72
59.89
48.75
46.10
51.06
52.12
75.38
74.40
75.94
74.23
65.09
65.78
77.15
74.17
73.27
64.05
61.20
51.32
49.49
54.67
51.70
51.20
4.34
4.71
4.81
4.57
4.52
4.68
4.81
4.75
5.03


a In all samples except milk, protein is N x5.70;


in milk it is Nx 6. 25.


The hard Scotch Fife spring wheat selected for the experiments
(sample No. 153) was characterized by a very high protein content,
namely, 15.5 per cent. In an earlier publication of this Department
showing the average composition of a large number of American feed-
ingstuffsa the protein content of wheat is given as 11.9 per cent. The
highest percentage of protein there recorded is 17.2 per cent and the
lowest 8.1 per cent. It will be observed that the wheat from which
these flour samples were obtained contained nearly this maximum
amount of proteid material. In the investigations with hard wheat

Previously reported,b the wheat employed contained 12.65 per cent
protein. The average amount of protein in the same variety of wheat

aU. S. Dept. Agr., Office of Experiment Stations Bul. No. 11, p. 17.
BU. S. Dept Agr., Office of Experiment Stations Bul. No. 101.


153
154
155
166
167
158
159
160
161
162
163
164
182
199
217
218
219
221
237
. 238
289
240
241
242
267
268
223
231
244
251
260
165
181
198
216
224
232
243
258
259


Heat of
combtui-
A.h. tion per
gram,
deter-
mined.

Per cnat. Calories.
1.93 4.023
.98 3.877
01 3.971
.68 3.861
.39 3.960
.46 3.904
1.00 4.072
2.19 4.112
4.09 4.430
5.43 4.314
7.31 4.187
.77 2.535
1.39 2.495
.50 2.594
.51 2.647
1.85 4.090
1.66 4.020
.53 4.010
1.83 4.000
3.96 4.256
6.11 4.108
.46 3.799
1.28 3.860
1.85 3.906
3.20 ..........
6.72 .........
.51 2.710
1.46 2.640
.49 2.610
1.27 2.690
1.45 2.620
.80 .700
.89 .746
.74 .729
.76 .744
.79 .780
.77 .813
.77 .742
.73 .735
.77 .777









14

is found to vary materially from year to year, depending among other
things upon the amount of rainfall and the climatic conditions under
which the wheat has matured. The wheat crop produced in the north-
western United States in 1900 was unusually rich in protein. The
rainfall and climatic conditions seemed to be particularly favorable for
producing wheat and other grains with a high nitrogen content. While
the wheat employed in this investigation contained somewhat more
protein than is found in average wheat, in the author's opinion the
percentage is no greater than in average wheat grown in the north-
western United States in 1900. All of the flour samples from'this
wheat were relatively richer in protein than those in similar investi-
gations with hard wheat in 1898-99, owing to the high nitrogen con-
tent of the wheat. The differences in the protein content of the several
grades of flour ground from the wheat were comparatively small.
There was a higher percentage of fat in the middlings than in the
bran, owing to the presence of the germ in the former. Red-dog flour
is the richest, as regards both fat and protein, of the products ground
from the wheat. In the case of the patent and clear grades of flour,
the heat of combustion as determined was found to agree closely with
the heat of combustion obtained by calculation, using the usual factors,
namely, 9.3 calories per gram a for fat, 5.9 for protein, and 4.2 for
carbohydrates. As pointed out in a previous report,b the percentage
of ash in the various products of wheat was lowest in the first
patent flour and highest in the red-dog flour. Each grade of flour,
beginning with the first patent, was found to contain proportionally
more ash than the preceding grade. In fact, as noted previously, the
grade of flour can be determined from the amount of ash present. In
the analyses reported above the ash content is greater than in-the-
samples employed in the earlier work with hard wheat in this labora-
tory. There appears to be a close relationship between the amounts
of ash and protein present in flour and other milled products of wheat,
any material increase in protein being accompanied by a correspond-
ing increase in mineral matter. This has often been attributed to the
phosphorus associated with the proteids. Late work of Osbornee
indicates that the total amount of phosphorus in wheat proteids is
too small to account for the increase in mineral matter just alluded to.
The distribution of the nitrogen and ash constituents of the wheat
berry has been frequently studied, and it is interesting to note some
comparatively recent American work on the subject, particularly as
the investigations were made with wheats grown in the United States,
which are therefore directly comparable with the wheats used in the
investigation reported in this bulletin.
Mrs. Ellen H. Richards and Miss Lottie A. Braggd studied the distri-
aU. S. Dept. Agr., Office of Experiment Stations Bul. 101, p. 12. Ib., p. 9.
c Connecticut State Station Rpt. 1900, p. 464. cdTech. Quart., 3 (1890), p. 246.








15


button of nitrogen and phosphorus in winter and spring wheat and
their milling products, in both cases the milling products having been
ground from the same lots of wheat. The results obtained are shown
in the following table, which includes also values for protein obtained
by multiplying the figures for nitrogen by 6.25:

TABLE 2.-Nitrogen and phosphorus in wheat and its milling products.


Phos-
Milling r:roducts. Water. phor .

St. Louis winter wheat: Per cent. Per cent.
Whole wheat............................................ 12.85 0.262
Royal patent flour......................... .... .......... .... 13.37 .051
Extra fancy flour ....................................... 12.51 .100
Low-grade flour.......................................... 11.94 .100
Middlings ............................................... 11.21 .225
Bran ..................................................... 12. 15 .828
Minnesota spring wheat:
Whole wheat.......................................... 11.09 .230
Patent flour.............................................. 12.29 .050
Bakers' flour............................................. 12.14 .091
Shorts.................................................... 11.27 .560
Bran ................................................... 11.23 .830


Nitrogen. N' ,,1ei.
"N x 6.25).,

P-r crrt. Pcr cent.
1.87 11.7
1.39 8.7
1.78 11.1
2.08 13.0
2.73 17.1
2.62 16.4
2.24 14.0
2.10 13.1
2.40 15.0
2.78 17.4
2.55 15.9


The figures in the table indicate that, while a larger part of the protein
is recovered in the flour than is the case with the phosphorus, there is,
nevertheless, a parallelism in the proportion of protein and phosphorus
in the different milling products.
At the Arkansas Experiment Station, Teller" made a very thorough
and detailed study of the ash constituents of a sample of locally grown
medium hard winter wheat and its milling products. In milling 3,000
pounds of uncleaned wheat, 1.83 per cent was recovered as screenings
and 0.33 per cent as tailings, the percentage of milling products being
as follows: Patent flour 25.80, straight flour 42, low-grade flour 3.87,
dust room contents,1.17, ship stuff 1.13, and bran 23.80. The loss of
material in grinding-that is, the material unaccounted for-was
therefore only 0.07 per cent.
The principal ash constituents and the sulphur and nitrogen in the
whole wheat and the different milling products were as follows:

TABLE 3.-Ash constituents and nitrogen of winter wheat and its milling products.


Milling products.


Wheat......................
Patent flour ..............
Straight flour.............
Low-grade flour...........
Dust room material.......
Ship stuff.................
Bran .....................


Total
ash.b


Per ct.
1.62
.31
.40
.70
2.50
3.08
5.25


In total ash.


Silica.


Per ct.
1.04
2.33
1.28
.50
1.34
.49
.97


Ferric
oxid.

Per ct.
0.27
.47
.26
.25
.30
.37
.27


Potash. Lime.


Per ct.
29.70
38.50
36.31
32.27
30.85
28.03
28.19


Per ct.
3.10
5.59
5.65
4.51
3.53
2.80
2.50


Mag-
nesia.

Per ct.
13.23
4.39
6.44
9.33
12.90
13.27
14.76


Phos-
phoric
acid.

Per ct.
52.14
48.05
49.32
53.10
49.94
54.62
52.81


Sul- Nitro-
phur. gen.


Per ct. Per ct.
0.13 1.96
.09 1.54
.10 1.75
.16 2.13
.15 2.17
.17 2.78
.21 2.73


aArkansas Station Bul. 42, pts. 1, 2.
bThis sum includes values which are given for alumina, chlorin, zinc, and sulphur trioxid, which
are not quoted in the table. The author regards the values for sulphur present in the different
materials as more reliable than those for sulphui trioxid in the ash, owing to a probable volatilization
of alphur in burning to obtain the ash. The other constituents omitted are not of much importance,
the luimina IadL zic being accidentally present.






16

Teller points out that about 87.5 per cent of the entire phosphoric
acid, 78.5 per cent of the potash, and 37.5 per cent of the nitrogen
present in the wheat berry are recovered in the milling products
ordinarily used as cattle feeds. As will be seen from the above table,
the percentage of phosphoric acid increases as the grade of four
decreases, being least in the patent flour and greatest in low-grade
flour, the proportion present in the latter being greater than in any of
the milling products except ship stuff; in other words, as shown by these
figures, the phosphoric acid content, generally speaking, increases in
passing from the center of the wheat berry to the outer layer, the
inner portion yielding the fine flour and the outer portion the bran.
The table also shows that in the various milling products the propor-
tion of nitrogen (and hence that of protein, since the latter is computed
by multiplying nitrogen by a constant factor) varies in practically the
same way as the phosphorus.
The parallelism between protein and phosphorus, which was spoken
of above, is borne out by the analytical data quoted, though it does
not necessarily follow that the phosphorus present occurs in the true
proteids.
As a whole, it has been the aim in the experiments conducted at the
University of Minnesota to include standard types and varieties of
hard and soft wheat flours, milled under different conditions. The
differences in the percentages of flour recovered from the wheat used
necessarily make slight differences in the composition and character-
istics of the grades of flour obtained. The soft wheat products were
of different character from the samples of similar products from hard
wheat. The hard wheats had been exhaustively milled, as is the
usual custom, in one of the large mills of Minneapolis, while the soft,
winter wheats were ground by mills of smaller capacity using some-
what different milling systems, and, as is the general commercial prac-
tice, were less exhaustively milled.
In general, the flours from soft wheat were somewhat similar to,
though not in every respect like those from, hard wheat, because of
the differences in the kinds of wheat used and percentages of flour
recovered. The graham flour contained the largest percentage of pro-
tein, fat, and ash, while the patent grades of flour contained the small-
est amounts of these ingredients. A noticeable difference in the
mechanical composition of the three grades of soft wheat flour was
observed. With the process of milling followed, some granular mid-
dlings were left in the offals which would have been recovered in the
straight and other grades of flour with more exhaustive milling. This
results in a straight-grade flour containing slightly less protein than
the product of exhaustive milling, as the granular middlings are rich
in this nutrient. The particles or granules of the graham flour were






I:


much larger than those of either the entire-wheat or the straight-grade
flour. The comparative sizes of granules from graham, entire-wheat,
and straight-grade flours ground from soft wheat are shown in the
micro-photographs reproduced in Plate I, figs. 1 and 2, and Plate II,
fig. 1, p. 48.


COMPOSITION OF FECES AND URINE OBTAINED IN DIGESTION
EXPERIMENTS.


The composition of the dry matter of the feces from the digestion
experiments is given in Table 4, while Table 5 records the amount,
specific gravity, and percentage of nitrogen of the urine.
A description of the samples of feces and urine follows:

Nos. 178, 199, 180, 195, 196, 197, 213, 214, and 215 represent the feces which were
obtained in the digestion experiments with hard spring wheat products.
Nos. 225, 226, 227, 233, 234, 235, 245, 246, 247, 252, 253, 254, 261, 262, and 263, the
feces which were obtained in the digestion experiments of 1901-2 with soft winter
wheat.
Nos. 166-177, 183-194, and 200-212, the urine from the digestion experiments with
hard spring wheat products.
Nos. 228, 229. 230, 236, 237, 238, 248, 249, 250, 255, 256, 257, 264, 265, and 266, the
urine obtained in the experiments with soft winter wheat.


TABLE 4.-Composition of dry matter of feces from digestion experiments with hard and
soft wheat breads.


Whence obtained.


Experiments with hard wheat:
Experiment No. 242.................
Experiment No. 243.................
Experiment No. 244.................
Experiment No. 245.................
Experiment No. 246.................
Experiment No. 247.................
Experiment No. 248.................
Experiment No. 249.................
Experiment No. 250 .................
Experiments with soft wheat:
Experiment No. 309.................
Experiment No. 310 ..................
Experiment No. 311.................
Experiment No. 312.................
Experiment No. 313..................
Experiment No. 314.................
Experiment No. 315.................
Experiment No. 316................
Experiment No. 317...................
Experiment No. 318.................
Experiment No. 319.................
Experiment No. 320.................
Experiment No. 321.................
Experiment No. 322 ..................
Experiment No. 323.................


19047-No. 126-03-2


Protein
(N x6.25).



Per cent.
30.25
28.37
25.00
23.25
23.31
21.67
29.94
28.56
23.94
14.10
21.83
26.75
14.31
16.76
20.06
22.61
23.13
25.34
17.94
21.00
18.67
19.50
17.86
19.13


Fat.



Per cent.
12.26
7.45,
7.44
8.70
5.61
6.41
17.46
11.44
9.30
17.04
15.84
9.10
5.36
10.32
4.32
8.58
13.13
15.26
5.31
11.65
6.00
6.44
13.98
8.25


Heat of
combus-
Carbo- Ash. tion per
hydrates. gram
deter-
mined.

Per cent. Per cent. Calories.
34.42 23.07 4.63,
35.37 28.81 4.070
41.35 26.21 4.351
50.16 17.89 4.415
47.59 23.49 3.960
50.48 21.44 4.170
25.02 27.58 4.720
26.42 33.58 4.265
36.47 30.29 4.654
45.15 23.71 5.030
38.92 23.41 5.300
39.40 24.75 4.400
60.48 19.85 4.340
55.98 16.94 4.420
56.51 19.11 4.160
43.99 24.82 5.050
38.92 24.82 5.160
32.59 26.81 5.360
56.28 20.47 4.290
46.38 20.97 4.410
51.76 23.57. 3.990
57.06 17.00 4.220
51.14 17.02 4.470
52.68 19.94 4.170


Sample
No.


178
179
180
195
196
197
213
214
215
225
226
227
233
234
235
245
246
247
252
253
254
261
262
263




r


18

TABLE 5.-Amount, specific gravity, and nitrogen of urine from digestion experiments wif
hard and soft wheat breads.

a leSubjectTotal
SampleSuN t Whence obtained. amout g mNIt e.
No. voided. grvity.

Experiments with hard wheat:
Experiment No. 242- Grams. PerC t.
166 1 First day ................................ 1,368.0 1.06 LU
169 1 Second day.................................. 1, 350.0 LO 45
172 1 Third day .................................... 1,463.5 1. 02 W
175 1 Fourth day................................... 1,326.0 1.029 L74
Experiment No. 243-
167 i 2 First day ..................................... 1,805.0 1.016 .8
170 2 Second day................... ...... ....... 2,112.0 1.015 .96
173 2 Third day.................................... 2,298.0 1.015 LO
176 2 Fourth day................................... 2,248.0 1.017 .98
Experiment No. 244-
168 3 First day...................................... 1,991.0 1.00 1.3
171 1 3 Second day....................... ....... 1,720.0 1.021 1.41
174 3 Third day...........-...-.........-.......... 1,679.0 1.06 172
177 3 Fourth day................................... 1,947.0 L028 L45
Experiment No. 245-
183 1 First day....................... ........... 1,270.0 1.090 1.8
186 1 Second day.................................. 1,210.0 1.030 1.79
189 1 Third day ................................. 1,212.0 1.030 1.84
192 1 Fourth day................................. 1,102.0 1.028 1.88
Experiment No. 246-
184 2 First day .................................. 1,943.0 1.015 LO
187 2 Second day......... -....... ........... 1,732.0 1.015 IO1
190 2 Third day ..................................... 2,188.0 1.015 .95
193 2 Fourth day................................... 2,368.0 1.014 -.90
Experiment No. 247-
185 3 First day .................................... 1,851.0 1.024 1.39
188 3 Second day.................................. 1,581.0 1.025 172
]91 3 Third day .................................. 1,614.5 1.027 -176
194 3 Fourth day................................. 1,338.0 1.027 1.94
Experiment No. 248--
200 1 First day ................................... 1,124.0 1.027 1.77
204 1 Second day .................................. 1,077.0 1.031 2.10
207 1 Third day .......................-............ 1,068.0 1.090 L90
210 1 Fourth day......................................1,110.0 1.029 2.01
Experiment No. 249--
201 2 First day ................................... 1,943.0 1.014 1.02
205 2 Second day..................................i 1,698.0 1.015 .00
208 2 Third day ................................. 2,2.0 1.01 .97
211 2 Fourth day................................ 2,023.U 1.014 .97
Experiment No. 250--
203 3 First day .................................... 1,123.0 1.028 1.8
206 3 Second day.. ................................. 1,242.0 1.026 1.81
209 3 Third day ..................................... 1,601.0 1.022 1.56
212 3 Fourth day................................. 2,463.0 1.016 1.07
Experiments with soft wheat:
228 1 Experiment No. 309............................... 6,023.1 1.016 1.10
229 2 Experiment No. 310 ............................... 4,296.2 1.020 LS0
230 3 Experiment No. 311............................... 4,486.2 1.019 1.31
236 1 Experiment No. 312............................ 5,652.9 1.019 1.21
237 2 Experiment No. 313............................... 5,201.7 1.020 1.41
238 3 Experiment No. 314............................... 4,115.6 1.022 .L4
248 1 Experiment No. 315 .............................. 7,317.4 1.016 1.19
249 2 Experiment No. 316.............................. 6,556.6 1.019 1.41
250 3 Experiment No. 317 ............................. 4,747.6 1.020 1.3
255 1 Experiment No. 318............................... 7,889.1 1.016 1.07
256 2 Experiment No. 319................................ 6,910.1 1.020 1.47
257 3 Experiment No. 320............................... 5,476.6 1.021 1.61
264 1 Experiment No. 321 .............................. 5,210.1 1.020 1.41
265 2 Experiment No. 322............................... 4,532.0 1.020 1.16
266 3 Experiment No.323........................ ....... 4,508.8 1.022 1.80


EXPERIMENTAL METHODS.

The methods followed in all of the experiments here reported are
practically identical with those described in detail in the previous
publication a already referred to, and need only be briefly outlined.
The bread from the different sorts of flour was eaten with milk; the
amount of either was not limited, but the quantities eaten at each meal
were recorded. The separations of the feces were made by means of

a U. S. Dept. Agr., Office of Experiment Stations Bul. 101.






19


charcoal taken with a meal of bread and milk, which giies feces of a
characteristic color and consistency. The digestibility of the nutrients
of the diet as a whole was taken as the difference between the amounts
in the food and those in the feces, no attempt being made to determine
the metabolic products of the feces.a
In order to compute the digestibility of the nutrients of the bread
alone, it was assumed that 97 per cent of the protein, 95 per cent of
the fat, and 98 per cent of the carbohydrates of milk were digested.
The undigested nutrients of the milk as calculated by the use of these
factors subtracted from the nutrients of the total feces give the esti-
mated undigested nutrients from bread, which, subtracted from the
total nutrients of the bread, give the digestible nutrients in bread.
The latter, divided by the total nutrients in the bread, give the coeffi-
cients of digestibility of bread alone.
The values used for the digestibility of the nutrients of milk have
been deduced from the results of. a large number of digestion experi-
ments with milk. Even if, in the experiments here reported, the diges-
tibility of the milk nutrients varied from these assumed coefficients,
the figures for the digestibility of the nutrients of the different kinds
of bread are still strictly comparable because the same factors for
milk were used in all cases.
As has been already explained,b the energy of the estimated feces
from bread alone was computed by proportion from the energy of the
total feces. The ratio of the heat of combustion of the bread feces
as computed by factors to the actual energy was assumed to be the
same as the ratio of the computed energy of total feces to the heat of
combustion as determined.
Although the energy of the urine was determined, in the calculation
of the availability of the energy of the" total food and of the bread
alone, it was assumed, for the sake of uniformity with experiments
previously reported, that 1.25 calories of energy would appear in the
urine for every gram of digestible protein in the total food or in the
bread alone. For the sake of making an approximate estimate of the
available energy in those experiments where the digestibility of the
bread fat could not be computed, it was assumed that 90 per cent of
alt should be observed that the results thus obtained do not represent actual
digestibility. The true digestibility could be found by subtracting from the ingredi-
ents of the food the corresponding ingredients of the feces that come only from undi-
gested portions of the food. But no satisfactory method has been found for separating
these from the metabolic products in the feces, which consist largely of the residues
of the digestive juices that have not been reabsorbed. These latter represent the
cost of digestion as expressed in terms of food ingredients. What the results of these
experiments do represent, therefore, is the proportions of the food, or of the several
ingredients, that are available to the body for purposes other than digestion itself.
In n accordance with common usage, however, the term digestibility, which indicates
Sthe apparent digestibility, has been employed here; the term availability is some-
j:imes used to express the same idea.
SbU. S. Dept. Agr., Office of Experiment Stations Bul. 101, p. 22.







20

the fat of the bread was digestible. The results thus found would
probably be below rather than above what was actually the case.
As in the preceding experiments, the balance of income and outgo
of nitrogen was learned by determining the daily amounts ingested
in the food and excreted in the urine and feces. In the experi-
ments with soft winter wheat in 1901-2 determinations were also made
of the phosphoric acid in the samples of food, feces, and urine. Such
data, however, are reserved for further study.
The particular difference between the digestion experiments given
here and those formerly reported is in the length of the experimental
period, this being four days long here and only two in the earlier
experiments. The longer experimental period is believed to be pref-
erable, because it is generally considered that there is less danger
of error due to uncontrollable factors that may vitiate the results in
a short digestion period.
As is well known, the results obtained from a digestion experiment
are not absolute, but only relative. But inasmuch as in the diges-
tion experiments reported in this bulletin the object is to deter-
mine the relative rather than the absolute digestibility of three
different kinds of bread, it is believed that the results obtained are
satisfactory for this purpose, because whatever error may be intro-
duced in one experiment is introduced alike in all of any given series,
since the conditions were kept uniform throughout the series. While
the results of a single digestion experiment are open to criticism, the
results obtained from a series of experiments are much less so and are
of value in determining whether one food is more digestible than
another under similar experimental conditions. Hence in discussing
the results obtained from these digestion experiments they are con-
sidered in relation to one another rather than alone.
DETAILS OF THE DIGESTION EXPERIMENTS WITH BREAD FROM
DIFFERENT GRADES OF HARD SPRING WHEAT FLOUR.
The details of the digestion experiments with hard wheat products
are given in the following pages. Nine digestion experiments, each of
four days' (or twelve meals') duration were made with three different
subjects. In every case the diet consisted of bread and milk, and all of
the experiments were conducted in the same manner, except that bread
made from a different kind of flour was used in each series. In making
the bread no shortening or milk was used, but simply yeast, flour, salt,
and water.
The subjects were university students who spent from three to four
hours each day at light muscular work out of doors. All had served
as subjects in former digestion experiments and were thoroughly
familiar with the requirements of such work.
The experiments were practically made in triplicate-that is, the
same kind of an experiment was made with each of three subjects at







21

the same time. The order in which they were conducted was as follows:
The first series of experiments (with entire-wheat bread) extended
from April 17 to April 20, inclusive; the second series (with graham
bread) from April 23 to April 26, inclusive; and the third series (with
bread from standard patent flour) from May 1 to May 4, inclusive.
The experiments were taken up in this order because of the difficulty
experienced in previous experiments with a graham bread and milk
diet. It was believed that the investigation could be conducted to
better advantage by having the graham bread experiment between the
others, rather than at the beginning or close of the series. The four
days' diet of graham bread and milk caused a slight irritation of the
digestive tract and a slight attack of gastritis with two of the subjects.
The following tables, Nos. 6 to 14, and the accompanying data show
the kind of food consumed, the subject experimented upon, the body
weight at the beginning and at the close of the experiment, and the
date and duration. Then follow statistics of the total nutrients in
the food and the feces, and the heat of combustion of each, and after
each of the tables statistics are given of tlajncome and outgo of
nitrogen during the experiment.

DIGESTION EXPERIMENT NO. 242.

Kind offood.-Milk, and bread made from entire-wheat flour.
Suject.-University student No. 1, 22 years old, employed about
four hours per day at manual labor.
Weight.-At the beginning of the experiment, 168 pounds; at the
close, 168 pounds.
Duration.-Four days, with twelve meals, beginning with breakfast
April 17, 1901.
TABLE 6.-Results of digestion experiment No. 242.

SWeight r Heat of
Sample Protein. Fat. Crbo Ash. combus-
No. material, hydrates. tion.

Food consumed: Grams. Grams. Grams. Grams. Grams. Calories.
164 Bread .................... 3,550.0 330.9 6.7 1,730.7 27.3 8,998
166 Milk..................... 9,950.0 323.4 378.1 431.8 79.6 6,965
Total ................... ........ 654.3 384.8 2,162.5 106.9 15,963
178 Feces (water free).............. 214.0 64.7 26.2 73.7 49.4 992
Estimatedfeces from food other
than bread ............................. 9.7 .......... 8.6 ....................
Estimated feces from
bread.............. .... .......... 55.0 .......... 65.1 ................
Total amount digested ........ .......... 589.6 358 6 2,088.8 57.5 14,971
Estimated digestible nutrients
in bread ................. ... ......... 275 9 .......... 1,665.6 ...................
Coefficients of digestibility of Per cent Per cent. Per cent. Per cent. Per cent. Per cent.
total food ................... .......... 90.1 93.2 96.6 53.8 93.8
Estimated coefficients ot diges-
tibihty of bread ...................... 83.4 .......... 96.2 .......... a93.0
Proportion of energy actually
available to body:
In total food............ .... .................... ........ .. ...........88.2
In bread alone ....... ........ ..... ........ ....a 89.1
I a. Estimated on the assumption that 90 per cent of the fat in the bread is digestible.









22


During this experiment the subject eliminated 5,508 grams urine,
containing 88.42 grams nitrogen. The average nitrogen balance per
day was therefore as follows: Income in food, 27.47 grams; outgo in
urine, 22.10 grams and in feces, 2.59 grams, implying a gain of 2.78
grams nitrogen, corresponding to 17.4 grams protein.


DIGESTION EXPERIMENT NO. 243.

Kind offood.-Milk, and bread made from entire-wheat flour.
Subject.-University student No. 2, 22 years old, employed about
four hours per day at manual labor.
Weight.-At the beginning of the experiment, 156 pounds; at the
close, 155 pounds.
Duration. -Four days, with twelve meals, beginning with breakfast
April 17, 1901.

TABLE 7.-Results of digestion experiment No. 243.


OR


Food consumed:
Bread ............. ........
Milk............ ........
Total .....................
Feces (water free)............
Estimated feces from food other
than bread ..................


Weight
of
material.i


Protein.


Fat.


Grams. Grams. Grams.
3,101.0 289.0 5.9
12,310.0 400.1 467.8
.......... 689.1 473.7
180.0 51.1 1 13.4
.......... 12.0 ..........


Carbo-
hydrates.


Grams.
1,511.8
534.3
2,046. 1
63.7


10.7


Heat of
Ash. eombnf,-
tlon.


Grams.
23.9
98.5
122.4
51.9


- 1I 1


CaOoria.
7,860
8,617
16,477


bread...... ... ............... .. 39.1 .......... 53. ........
Total amount digested ......... .......... 638.0 460.3 1982.4 70.6 15,744
Estimated digestible nutrients 03 1,927
in bread................... ......... 249.9 ..........1,458.8 ....................


Coefficients of digestibility of
total food....................
Estimated coefficients of digest-
ibility of bread ...............
Proportion of energy actually
available to body:
In total food ...........
In bread alone .............


Per cent.
... .......


Per cent.
92.6
86.5


Per cent. Percent.
97.2 96.9
.......... 96.5


a Estimated on the assumption that 90 per cent of the fat in the bread is digestible.

During this experiment the subject eliminated 8,463 grams urine,
containing 80.95 grams nitrogen. The average nitrogen balance per
day was therefore as follows: Income in food, 28.68 grams; outgo in
urine, 20.24 grams, and in feces, 2.09 grams, implying a gain of 6.35
grams nitrogen, corresponding to 39.7 grams protein.


Sample
No.


Per cent.
57.6
..........


..........


Per can
96.6
a90.4

90.7
a.9.0








23

DIGESTION EXPERIMENT NO. 244.

Kind offood.-Milk, and bread made from entire-wheat flour.
Subject.-University student No. 3, 24 years old, employed about
four hours per day at manual labor.
Weight.-At the beginning of the experiment, 161 pounds; at the
close, 160 pounds.
Duration.-Four days, with twelve meals, beginning with breakfast
April 17, 1901.

TABLE 8.-Results of digestion experiment No. 244.

Samp, Weight Carbo- Heat of
hmp1le of Protein. Fat. hdras. Ash. combus-
No. material, races tion.

Food consumed: Grams. Grams. Grams. Grams. Grams. Calories.
164 Bread ....................... 3,760.0 350.4 7.1 1,833.1 28.9 9,530
165 Milk ....................... 14,843.0 482.4 564.0 644.2 118.8 10,390
Total...................... .......... 832.8 571.1 2,477.3 147.7 19,920
180 Feces (water free) ............. 215. 1 53.8 16.0 88.9 56.4 936
Estimated feces from food other
than bread ................... .......... 14.5 .......... 12.9 .......... ........
Estimated feces from
bread.................. ..... ... 39.3 ......... 76.0 .....
Total amount digested ........ ......... 779.0 555.1 2,388.4 91.3 18,984
Estimated digestible nutrients
'in bread ................. ....... ..... 311.1 .. ..... 1,757.1 .......... ..........

Coefficients of digestibility of Per cent. Per cent. Per cent. Per ceid. Percent. Per cent.
total food.............................. 93.5 97.2 96.4 61.8 95.3
Estimated coefficients of digest-
ibility of bread ....... ................ 88.8 .......... 95.9 :......... a94.3
Proportion of energy actually
available to body:
In total food .............. ..................... .......... ................ 90.4
In bread alone ...................... ........... ............. .. ..............a90.2

a Estimated on the assumption that 90 per cent of the fat in the bread is digestible.

During this experiment the subject eliminated 7,337 grams urine,
containing 108.24 grams nitrogen. The average nitrogen balance per
day was therefore as follows: Income in food, 34.66 grams; outgo in
urine, 27.06 grams, and in feces, 2.15 grams, implying a gain of 5.45
grams nitrogen, corresponding to 34.1 grams protein.

DIGESTION EXPERIMENT NO. 245.

Kind offood.-Milk, and bread made from graham flour.
Subject.-University student No. 1.
Weight.-At the beginning of the experiment, 168 pounds; at the
close, 167 pounds.
Duration.-Four days, with twelve meals, beginning with breakfast
April 23, 1901.









24

TABLE 9.-Remuits of digestion experiment No. 246.


Sample
No.


18I


182
181


195


Food consumed:
Bread ......................
Milk......................
Total ...................
Feces (water free) ............
Estimated feces from food other
than bread ..................
Estimated feces from
bread..................
Total amount digested........
Estimated digestible nutrients
in bread .....................

Coefficients of digestibility of
total food ..................
Estimated coefficients of digest-
ibility of bread.............
Proportion of energy actually
available to body:
In total food................
In bread alone .............


Weht Protein.
material.

Grams. Grams.
3,342.0 318.8
10,207.0 319.5
.......... 638.3


Fat.


Grams.
9.7
408.3
418.0


Carbo-
hydrates.

Grams.
1,540.7
480.8
2,021.5


Ash. m


Grams.
46.5
90.8
137.3


Oalores.
8,3387
7,614
15, gSl


300.1 69.8 26.1 150.5 58.7 1,25
.......... 9.6 20.4 9.6 .......... 93

......... 60.2 5.7 140.9 .......... 1,02


.......... 568.5 391.9
.......... 258.6 4.0

Per cent. Per cent. Per cent.
.......... 89.1 93.8
.......... 81.1 41 2


.......... I ---------- ----------


1,871.0
1,399.8

Per cent.
92.6
90.9


88.6


Per cent.
60.9
..........


----------


14,i26
7,814

Per cea.
91.7
87.7

87.2
88.9


During this experiment the subject eliminated 4,794 grams urine,
containing 87.79 grams nitrogen. The average nitrogen balance per
day was therefore as follows: Income in food, 26.74 grams; outgo
in urine, 21.95 grams, and in feces 3.79 grams, implying a gain of 1
gram nitrogen, corresponding to 6.3 grams protein.

DIGESTION EXPERIMENT NO. 246.

Kind offood.-Milk, and bread made from graham flour.
Subject.-University student No. 2.
Weight.-At the beginning of the experiment, 154 pounds; at the
close, 152.7 pounds.
Duration.--Four days, with twelve meals, beginning with breakfast
April 23, 1901.


TABLE 10.-Results of digestion experiment No. 246.


Sample
No.

Foot consumed:
182 Bread...................
181 Milk......................
Total ....... ............
196 Feces (water free)..............
Estimated feces from food
other than bread .............
Estimated leces Irom
bread......... ........
Total amount digested .......
Estimated digestible nutrients
in bread ....................


Weight Carbo- I
o0 Protein. Fat. h rb .
material hydrates.

Grams. IGrams. Grams. I Grams.
2,855. 0 272.4 8.3 1,316.2
10,568.0 330.8 422.7 497.8
.......... 603.2 431.0 1,814.0
259.0 60.4 14.5 123.3
........... 9.9 .......... 10.0

I .....


Ash.


Grams.
39.7
94.1
133.8
60.8
..........


..........1 50.5 .......... 113.3 ........
.......... 542.8 416.5 1,690.7 73.0
221.9 .......... 1,202.9 ..........


Heat of
combus-
tion.

Calories.
7,123
7,883
15,006
1,026


........

13,980









25

TABLE 10.-Results of digestion experiment No. 246-Continued.


Coefficients of digestibility of
total food................
Estimated coefficients of diges-
tibility of bread ..............
Proportion of energy actually
available to body:
In total food...............
In bread alone .............


a Estimated on the assumption


Weight Caro-Heat of
of Protein. Fat. h rats. Ash. combus-
material. s tion.

Per cent. Per cent. Per cent. Per cent. Per cent. Per cent.
......... 90.0 96.6 93.2 54.6 93.2
.......... 81.5 .......... 91.4 .......... U88.9

.......... ................... .......... .......... 88.6
.......... .......... ... .....8 ........... a 5.1

that 90 per cent of the fat in the bread is digestible.


During this experiment the subject eliminated 8,231 grams urine,
containing 81.73 grams nitrogen. The average nitrogen balance per
day was, therefore, as follows: Income in food, 25.16 grams; outgo
in urine, 20.43 grams, and in feces, 2.94 grams, implying a gain of 1.79
grams nitrogen, corresponding to 11.2 grams protein.


DIGESTION EXPERIMENT NO. 247.


.mind of food.-Milk, and bread made from graham flour.
Subject.-University student No. 3.
Weight.-At the beginning of the experiment, 161 pounds; at the
close, 157 pounds.
Duration.-Four days, with twelve meals, beginning with breakfast
April 23, 1901.


TABLE 11.-Results of digestion experiment No. 247.


Food consumed:
Bread .....................
M ilk.......................
Total ............ ........
Feces (water free).............
Estimated feces from food other
than bread ..................
Estimated feces from
bread..................
Total amount digested .......
Estimated digestible nutrients
in bread....................

Coefficients of digestibility of
total food.....................
Estimated coefficients of diges-
tibility of bread ..............
Proportion of energy actually
available to body:
In total food...............
In bread alone.............


Weight
material.

Grams.
3,440.0
12,475.0


Protein.


Grams.
328.2
390.5


Fat.


Grams.
10.0
499.0


Carbo-
hydrates.

Grams.
1,585.9
587.6


----I I I-- -1


267.7


718.7 509.0
58.0 17.2
11.7 ..........

46.3 .........


2,173.5
135.1
11.7


Ash.


Grams.
47.8
111.0


158.8
57.4


123.4 .........


_________________ __________________ __________ I I


Per cent.
..........


660.7 491.8
281.9 ..........

Per cent. Per cent.
91.9 96.6
85.9 ..........


2,038.4
1,462.5

Per cent.
93.8
92.2


Pec


Heat of
com-
bustion.

Calories.
8,583
9,306
17,889
1,116


101.4 16,773
...... ..........

r cent. Per cent.
63.9 93.8
...... 90.3

......89.2
...... a 86.2


a Estimated on the assumption that 90 per cent of the fat in the bread is digestible.


Sample
No.


Sample
No.


.......... .
.......... .. .. .








26

During this experiment the subject eliminated 6,385 grams urine,
containing 107.13 grams nitrogen. The average nitrogen balance per,
day was therefore as follows: Income in food, 30.01 grams; outgo in
urine, 26.78 grams, and in feces, 2.32 grams, implying a gain of 0.91
grams nitrogen, corresponding to 5.7 grams protein.

DIGESTION EXPERIMENT NO. 248.

Kind offood.-Milk, and bread made from straight patent flour.
Subject.-University student No. 1.
TWeight.-At the beginning of experiment, 164 pounds; at the close,
164 pounds.
Duration.--Four days, with twelve meals, beginning with breakfast
May 1, 1901.

TABLE 12.-Results of digestion experiment No. 248.

mpl Weight Carb Heat of
Sample of Protein. Fat. Carbo- Ash. combus-
No. material, hydrates. tion.

Food consumed: Grams. Grams. Grams. Grams. Grams. Cbl&rie
199 Bread ....................' 2,575.0 248.0 1.0 1,314.9 12.9 6,680
198 Milk.................... 10,583.0 321.7 404.3 509.0 78.3 7,715


Total .............. ......
213 Feces (water free)..............
Estimated feces from food other
than bread ..................
Estimated feces from
bread.................
Total amount digested .........
Estimated digestible nutrients
in bread ....................

Coefficients of digestibility of
total food....................
Estimated coefficients of digest-
ibility of bread ...............
Proportion of energy actually
available to body:
In total food ..............
In bread alone ............


.......... 569.7 405.3 1,823.9 91.2 14,3 5
152.0 45.5 26.5 38.0 41.9 717
.......... 9.6 20.2 10.2 .......... 30

.......... 35.9 .......... 27.8 ...................
......... 524.2 378.8 1,785.9 49.3 18,678
.......... 212.1 .......... 1,287.1 ..................

Per cent. Per cent. Per cent. Per cent. Per cent. c Pe cent.
.......... 92.0 93.5 97.9 54.1 96.0
.......... 85.5 .......... 97.9 .......... -94.8

........... ... ...... .......... ......... ............ 90.5
............ ............. ........................ 90.5
*eoae


a Estimated on the assumption that 90 per cent of the fat in bread is digestible.

During this experiment the subject eliminated 4,378 grams urine,
containing 85.44 grams nitrogen. The average nitrogen balance per
day was therefore as follows: Income in food, 23.79 grams; outgo in
urine, 21.38 grams, and in feces, 1.82 grams, implying a gain of 0.59
gram nitrogen, corresponding to 3.7 grams protein.

DIGESTION EXPERIMENT NO. 249.

i7nd of food.-Milk, and bread made from straight patent flour.
Subject.-University student No. 2.
Weiqg t.- At the beginning of the experiment, 152 pounds; at the
close, 151i pounds.
Duration.-Four days, with twelve meals, beginning with breakfast
May 1, 1901.










27

TABLE 13.-Results of digestion experiment No. 4f5.


Weight
material.


I I I


Food consumed:
Bread ...................
Milk......................
Total ...................

Feces (water free)..............
Estimated feces from food other
than bread ..................
Estimated feces from
bread..................

Total amount digested........
Estimated digestible nutrients
in bread.....................

Coefficients of digestibility of
total food...................
Estimated coefficients of digest-
ibility of bread..............
Proportion of energy actually
available to body:
In total food...............
In bread alone .............


a Estimated on the assumption 1


Grams.
2,790.0
11,717.0

..........
146.8

..........


Protein.


Fat.


-- I --
Grams. Grams.
268.7 1.2
356.2 447.6
624.9 448.8
41.9 16.8
10.7 ..........


.......... 31.2 ..........


....... .

Per cent.


583.0


432.0


237.5 ..........


Per cent.
93.3


Per cent.
96.3


hydrate.


Grams.


Iltat III
Asth. comlbus-
tion.


Grairs.


Calories.


1,424.6 13.9 7,237
.563.6 86.7 8, 542
1,988.2 i 100.6 15,779
38.8 49.3 626
11.3 .......... .... ......
11.3

27.5 .......... ..........

1,949.4 51.3 i 15,153
1,397.1 ....................


Per cent.
98.1


Per cent. Pr cent.
51.0 96.0


......-... 88.4 .......... 98.1 ........

t. ........90 ..........e.c n ....... ------at ii. b e.
.. . . ... ... .. . .. .-.... .

that 90 per cent of the fat in the bread is digestible.


a95.5

91.4
a91.4


During this experiment the subject eliminated 7,846 grams urine,

containing 77.52 grams nitrogen. The average nitrogen balance per
day was therefore as follows: Income in food, 26.05 grams; outgo in
urine, 19.38 grams, and in feces, 1.68 grams, implying a gain of 4.99
grams nitrogen, corresponding to 31.2 grams protein.

DIGESTION EXPERIMENT NO. 250.


Kind offood.-Milk, and bread made from straight patent flour.
Subject.-University student No. 3.
Weight.-At the beginning of the experiment, 152 pounds; at the
close, 155 pounds.
Duration.-Four days, with twelve meals, beginning with breakfast
May 1, 1901.


TABLE 14.-Resulls of digestion experiment No. 250.


Sample Weight I Carbo- Heat of
No. of Protein. Fat. rate Ash. combus-
material..e tion.
1 ~I


I
Grams. Grams. Grams.
3,080.0 300.0 8.0
13,055.0 441.3 541.8
.......... 741.3 549.8
167.0 40.0 15.5
.......... 13.2 ..........

......... 26.8 ..........

.......... 701.3 534.3
.......... 273.2 .........


Food consumed:
Bread ..............-.......
Milk...... ............

Total ..................
Feces (water free).............
Estimated feces from food other
than bread ...................
Estimated feces from
bread..................
Total amount digested.........
Estimated digestible nutrients
in bread.............. .....


Grams.
1,605.3
596. 6


Gramis.
15.7
99.2


1 I


2,201.9


114.9


60.9 50.6
11.9 ..........


49.0


Calories.
8,152
9,713


17,865
777


2, 141.0 64.3 17,088

1,556.3 .......... ..........


Sample
No.


__


.......... ..........
- - -









28

TABLE 14.-Results of digestion experiment No. 250-Continued.


Coefficients of digestibility of
total food...............
Estimated coefficients of diges-
tibility of bread ..............
Proportion of energy actually
available to body:
In total food...............
In bread alone ............


WeI ht
material.

Per cent.




..........


Protein.


Per cent.
94.6
91.1


Fat.


Per cent.
97.2


Carbo-
hydrates.

Per cent.
97.2
97.0


Ash.


Per cet.
56.0


:.:... .. ':






Heat of
eombut-
tion.

Per cent,
067
a94.5


90.8
a .,


Estimated on the assumption that 90 per cent of the fat in the bread is digestible.

During this experiment the subject eliminated 6,439 grams urine,
containing 94.25 grams nitrogen. The average nitrogen balance per
day was therefore as follows: Income in food, 30.76 grams; outgo in
urine, 23.56 grams, and in feces, 1.60 grams, implying a gain of 5.60
grams nitrogen, corresponding to 35.0 grams protein.


SUMMARY OF RESULTS OBTAINED WITH HARD SPRING WHEAT
PRODUCTS.

The following tables summarize the results of the digestion experi-
ments with hard spring wheat products reported in the foregoing pages.
The results are given for the whole ration in Table 15 and competed
for the different sorts of bread alone in Table 16. For purposes of
comparison, the results obtained in previous experiments in this
laboratory are also included, as well as the average digestibility of
the different kinds of bread as shown by the result of all the
experiments.

TABLE 15.-Summary of digestion experiments with hard spring wheat; digestibility of
nutrients and availability of energy of total food.

Eperi Kind of food. Protein. Fat. Eneg.
ExperN Subject Kind of food. Protein. Fat. Carbo-tery.
meNo. No.hydrates.


Milk and entire wheat bread..............
.....do............................... ..
.....do.................................
Average of 3..........................
Average of 3 (1899-1900)..............
Average of 6 ........................


Per cent. Per cent.
90.1 93.2
92.6 97.2
93.5 97.2
92.1 95.9
89.7 91.7.
90.9 93.8


Milk and graham bread .................... 89.1
.....do....................................... 90.0
.....do...................................... 91.9
Average of 3 ........................ 90.3
Average of 3 (1899-1900)............... 88.2
Average of 6 .......................... 89.3
Milk and white bread (standard patent)... 92.0
.....do..... ................................ 93.3
.....do............................ ......... 94.6
Average ol 3 ........................ 93.3
Average of 3 (1899-1900) ............... 91.4
Average of 6......................... 92.4


93.8
96.6
96.6
95.7
91.1
93.4
93.5
96.3
97. 2
95.7
92.4
91.5


Per cent.
96.6
96.9
96.4
96.6
95.1
95.8
92.6
93.2
93.8
93.2
91.1
92.2
97.9
98.1
97.2
97.7
97.6
97 7


Per ceat.
89.2
90.7
90.4
90.1
88.5
89.3
87.2
88.6
89.2
88.3
86.0
87.2
90.5
91.4
90.8
90.9
90.3
90.6


Sample
No.


swi n


- 1--l-


:_1 I







29

TABLE 16.-Summary of digestion experiments with, hard spring wheat; digestibility of
nutrients and availability of energy of bread alone.


xperi- Subject Kind of food. Protein.
meNo. No
No.


'arbo-Enry
hydrate. Energy.


Per cent. Per cent. Per cent.
242 1 Entire wheat bread .................................. 83.4 96.2 89.1
243 2 .....do ................................................ 86.5 96.5 90.0
i244 3 .....do ............................................... 88.8 95.9 90.2
Average of 3...................................... 86.2 96.2 89.8
Average of 3 (1899-1900) .......................... 80.4 94.1 85.5
Average of 6 ................................... 83.3 95.1 87.6
245 1 Graham bread........................................ 81.1 90.9 83.9
246 2 .....do ................................................ 81.5 91.4 85.1
247 3 .....do ............................................... 85.9 92.2 86.2
Average of 3..................................... 82.8 91.5 85.1
Average of 3 (1899-1900) ......................... 77.6 88.4 80.7
Average of 6.................................... 80.2 90.0 82.9
248 1 White bread (standard patent) ...................... 85.5 97.9 90.9
249 2 .....do................................................ 88.4 98.1 91.4
250 3 .....do ................................................ 91.1 97.0 90.3
Average of 3...................................... 88.3 97.7 90.9
Average of 3 (1899-1900) ........................ 85.3 97.5 90.1
Average of 6.................................... 86.8 97.6 90.5


It will be observed that the average coefficients of digestibility of
the protein and carbohydrates and of the available energy in the
ration consisting of milk and bread made from straight patent flour
ground from hard spring wheat were larger than in the rations of milk
and entire-wheat bread or milk and graham bread from the same lot
of wheat. Considering the calculated results for bread alone, in the
experiments here reported it appears that in the graham bread the
average digestibility of the protein is 82.8 per cent; of the carbohy-
drates, 91.5 per cent, and the available energy is 85.1 per cent. The
digestion coefficients for the graham bread are lower than for either
the entire-wheat bread or the straight patent flour bread. In the case
of the bread from entire-wheat flour 86.2 per cent of the protein was
digested, and in the straight patent flour bread 88.3 per cent, while
96.2 per cent of the carbohydrates in the entire-wheat flour bread and
97.7 per cent of those in the bread from the straight patent flour Were
found to be digestible.
An examination of the tables also shows in each of the series a range
of from 4 to nearly 6 per cent in the digestion coefficients of each of
the nutrients. This is probably due to differences in the digestive
powers of the three subjects. Thus, for example, subject No. 3
digested the bread made from straight patent flour, entire-wheat
flour, and graham flour more completely than either subject No. 1 or
No. 2. While individual differences are observed in the three series
of experiments, in every case it appears that each subject digested
the nutrients in the straight patent flour bread more completely than
the nutrients in either the entire-wheat bread or the graham bread.







30

Hence the results for the average digestibility in the different series
of experiments are strictly comparable.
The tables also compare the results of the experiments reported ia:
this bulletin and those formerly reported It will be observed that
although the digestion coefficients are somewhat larger in the experi-
ments here reported than in those of 1899-1900, there is a general
similarity of results. In both series the nutrients of the bread from
standard patent flour are the most and those of graham the least
digestible, the entire-wheat flour bread being between the two. These
experiments are regarded as strictly comparable. Considering the-
two years' investigations as a whole, six subjects were employed and
eighteen separate digestion experiments were made.
Table 16 gives the average digestibility of the nutrients and availa-
bility of the energy in the three kinds of bread as shown by the results
of the two series. It is believed that these figures show, with a fair
degree of accuracy, the comparative digestibility of the protein and
carbohydrates and availability of energy in bread made from the three
kinds of flour when milled from the same lot of hard spring wheat
and consumed under similar conditions. The results, considered as
a whole, show that the protein in the straight patent flour bread is
6.6 per cent more digestible than that of the graham bread, while the
carbohydrates are 5.6 per cent more digestible. The amount of avail- "
able energy in the straight-flour bread is also greater by 7.5 per cent
than that in the graham bread.
In Table 17 the total and digestible protein and carbohydrates and
total and available energy in the three different kinds of flour as milled
are given. These values for digestible nutrients and available energy
were obtained by multiplying the percentage of total nutrients and.
energy by the coefficients given in Table 17.

TABLE 17.-Percentages of digestible protein and carbohydrates, and available energy is
entire-wheat, graham, and straight patent flours as milled.

Protein (Nx 5.70). Carbohydrates. Energy per gram.
Grade of flour from hard spring wheat. Digesti- Totl.Digesti- Total. Avail
ble. ble. able.
'Per cent. Per cent. Per cent. Per cent, Per cent. Per cet.
Straight patent ........................ 13.60 12.01 72.04 70.31 3.861 8.510
Entire wheat ............................ 13.72 11.83 70.09 67.43 3.877 3.481
Graham.................................. 14.21 11.77 68.55 62.62 3.971 .3879

There was a somewhat larger amount of digestible protein in the
straight patent flour than in either the graham or entire-wheat flour.
In the straight patent flour there was 70.31 per cent of digestible..
carbohydrates, in the entire-wheat flour 67.43 per cent, and in the

aU. S. Dept. Agr., Office of Experiment Stations Bul. 101, p. 33.- .






31

graham flour 62.62 per cent; that is, the carbohydrates of the straight
patent flour were much more digestible than those of either the entire
wheat or graham flour. The amount of available energy of the straight
patent flour is also larger than that of either the graham or entire-
wheat flour.
On comparing the figures in this table with those previously reported a
it will be observed that the results for protein here given are higher.
This is due to two facts already pointed out, namely, that the per-
centage of protein in the wheat employed in these experiments was
higher, and the coefficients of digestibility were larger. The signifi-
cance of the results, however, is the same in both cases. Briefly stated,
the results of all of the experiments with hard spring wheat show that
the digestible protein and carbohydrates, as well as the amount of
available energy, are greater in the standard patent flour than in either
the graham or entire-wheat flour.
No marked variations in the balance of income and outgo of nitrogen
were observed in the different periods except such as were due to
differences in the amounts consumed. In other words, judged by the
data regarding the metabolism of nitrogen, the three sorts of breads
served the body equally well.
The results of these experiments confirm those of earlier work with
hard-wheat flours, and show that when breads made from straight
patent flour, entire-wheat flour, and graham flour, milled from the
same lot of hard spring wheat, are fed under uniform experimental
conditions to men, there is a larger amount of digestible protein and
carbohydrates and available energy in the patent flour than in either
the entire-wheat or graham flour, although judged by composition the
graham flour contains the most and the patent flour the least total
protein. The greater digestibility of the protein and carbohydrates
of the patent flour is regarded as due in part at least to the fineness
of division of the flour particles, or, in other words, to the fact that a
considerable portion of the nutrients in the graham and entire-wheat
flours are present in comparatively large particles, which resist the
action of the digestive fluids and so escape digestion. It has also been
suggested that the cell walls in the layer of the grain directly under
the bran are more resistant to digestive juices than the walls of cells in
the interior of the kernel (see pp. 48, 49). Thus while there is actually
somewhat more protein, pound for pound, in graham or entire-wheat
than in patent flour, the body obtains less protein and energy from
the coarser than it does from the finer flour, and whatever is gained
in composition by adding the bran or germ is offset by the loss in
digestibility.


all. S. Dept. Agr., Office of Experiment Stations Bul. 101, p. 33.






32

DETAILS OF THE DIGESTION EXPERIMENTS WITH BREAD FROX
DIFFERENT GRADES OF SOFT WINTER WHEAT FLOUR.

In order to determine whether the results obtained with bread from
hard-wheat flours would be the same with flours from wheat of a dif-
ferent character, fifteen digestion experiments were made with bread
from graham, entire-wheat, and standard patent flours milled from soft
winter wheat. The results of these experiments are reported on the
following pages.
Two sets of experiments were made. In one set, comprising the
first six of the following experiments, the flours used were prepared
from the same lot of Indiana soft winter wheat by a milling company
of Goshen, Ind. Only two kinds of flour were used in these six experi-
ments, one being a standard patent grade similar to but not quite the
same as the same grade of flour used in the experiments with hard
wheat; the other was a so-called entire-wheat flour, but was somewhat
coarser than this grade of flour prepared from hard wheat. In the
second set of experiments three grades of flours were used, all ground
from the same lot of Michigan soft winter wheat by a milling company
of North Lansing, Mich.
The experiments were made by the same methods as were followed
in earlier work with hard-wheat flours. The experiment proper was
preceded by a preliminary meal of bread and milk, charcoal being used
to mark the separation of the feces. The experimental period con-
tinued three days in the experiments with the Indiana flours, and four
days with the Michigan flours. The subjects were young men in good
health, designated as Nos. 1, 2, and 3. They were employed at farm
labor, office, and university work. One subject, No. 1, had been
employed in the digestion work of 1900 and 1901 as subject No. 3.
The subjects were allowed a diet of bread and milk, unrestricted as to
amount, the quantities consumed at each meal being carefully weighed.
The different series of experiments in which graham, entire-wheat,
and straight-grade flours were used were alike in all respects except
as regards the bread. The four days' diet of milk and graham bread
proved to be rather laxative. It was observed that the subjects who
were employed at the severest labor had a decided preference for the
bread made from the straight and mixed grade flours, while the one
employed at office and university work did not have so pronounced a
preference. In no case was the graham bread preferred.
Tables 18 to 32 record the data of the several digestion experiments.
DIGESTION EXPERIMENT NO. 309.
Kind offood.-Milk, and bread made from straight-grade flour.
Sulject.-Man No. 1; age, 25 years; employed at office work.
Weight.-At the beginning of the experiment, 161.25 pounds; at
the close, 162 pounds.








. 88

Duration.--Three days, with nine meals, beginning with breakfast
ppril 9, 1902.
TABLE 18.--Resulf. f digestion ex.perimrnt No. 309.

nWeight Cr iHeat of
NP. o1 Protein. Ft. hCarbo- Ash. combue -
o material. ydrate. tion.

Food consumed: rs. Grains. rGraimx. Granem. rams. Calories.
228 Bread ...................... 2,950.0 236.3 17.7 1,513.9 15.0 7,994
224 Milk......................... 9.850.0 ; 326.0 431.4 445.2 77.8 7,683
Total................................ 562.3 449.1 1,959.1 92.8 15,677
25 Feces (water free) ............. 166.0 23.4 2. 3 74.9 39.4 83
Estimated feces from food other r I
than bread........................... 9.8 21.6 8.9 .......... 347
Estimated feces from
S bread .................... .......... 13.6 6.7 66.0 .....48
Total amount digested......... ........ .538. 9 420.8 1,884.2 53.4 14,842
Estimated digestible nutrients I
in bread.. ........................ 222.7 11.0 1,447.9 .......... 7,506


Coeficients of digestibility of Per cent. Per cent. Per cent. Per cent. Per cent. Per cent
total food ............................. 95.8 93.7 96.2 57.5 94.7
Estimated coefficients of diges- ,
tlbility of bread........................ 94.2 62.1 95.6 ........... 93.9
Proportion of energy actually 6
available to body:
In total food..................................... .......... .................... i 90.4
In bread alone............................................................ 90.4


During this experiment the subject eliminated 6,023 grams urine,
containing 66.25 grams nitrogen. The nitrogen balance per day was
therefore as follows: Income in food, 31.20 grams; outgo in urine,
22.08 grams, and in feces, 1.25 grams, implying a gain of 7.87 grams
nitrogen, corresponding to 49.2 grams protein.

DIGESTION EXPERIMENT NO. 310.

Kind offood.-Milk, and bread made from straight-grade flour.
Subject.-Man .No. 2; age, 25 years; university student: employed
at average farm labor four hours per day.
Weight.-At the beginning and close of the experiment, 163.75
pounds.
Duration.-Three days, with nine meals, beginning with breakfast
April 9, 1902.
TABLE 19.-Results of digestion experiment No. 310.

Sample Weight Carbo- Heat of
INomal. of Protein. Fat.. hIds, Ash. combus-
material. hdraetion.

Food consumed: Grams. Grams. Grams. Grainms. Grams. Calories.
223 Bread ..................... 2,860.0 229.0 17.2 1,467.7 14.6 7,751
224 Milk....................... 7,8b0.0 259.8 343.8 354.8 62.0 6,123
Total ...................... .......... 488.8 361.0 1,822.5 76.6 13,874
-I
226 Feces (water free).............. 147.0 32.1 23.3 57.2 34.4 779
Estimated fecesfrom food other
than bread ................... .......... 7.8 17.2 7.1 ..... 287
Estimated feces from
bread............................. 24.3 6.1 50.1 ..........492

19047-No. 126-03-3




I



34

TABLE 19.-Results of digestion experiment No. 310-Continued.

--Weight --- IHhre
Sample rbo- Protein. Fat. Carb
._ lof Protein. Fat. Ash. oombtmS -
No. material. i hydrates.n,

Grams. Grams. Grams. Grams. Grams. Cories.
Total amount digested .........!......... 456.7 337.7 1,765.3 42.2 13,096
Estimated digestible nutrients I
in bread................... ...... 204.7 11.0 1,417.6 .......... 7,289

Coefficients of digestibility of Per cent. Per cent. Percent. Per cent. Per cent. Percent.
total food.......................... 93.4 93.5 96. 9 55.1 94.4
Estimated coefficients of diges-j
tibility of bread........................ 89.4 64.4 96.6 1.......... 98.6
available to body:
In total food ............. ........ ................. 90.
In bread alone .................................................... 90.4


During this experiment the subject eliminated 4,296 grams urine,
containing 64.61 grams nitrogen. The nitrogen balance per day was
therefore as follows: Income in food, 27.25 grams; outgo in urine,
21.54 grams, and in feces, 1.71 grams, implying a gain of 4 grams
nitrogen, corresponding to 25 grams protein.

DIGESTION EXPERIMENT NO. 311.

Kind of food.-Milk, and bread made from straight-grade flour.
Subject.-Man No. 3; 21 years of age, employed at average farm
labor.
Weight.-At the beginning of the experiment, 151.75 pounds; at the
close, 150.5 pounds.
Duration.-Three days, with nine meals, beginning with breakfast
April 9, 1902.

TABLE 20.-Results of digestion experiment No. 311.

SamWple eight Hrb- eat of
Sample of Protein. Fat. Carbo- Ash. combus-
No. material. hydrates. tion.

Food consumed: Grams. Grams. Grams. Grams. Grams. ClGories.
223 Bread ..................... 2,572.0 206.0 15.4 1,319.9 13.1 6,970
224 Milk....................... 6.771.0 224.1 296.6 306.1 53.5 5,281
Total ................. .... ........ 430.1 312.0 1,626.0 66.6 12,251
227 Feces (water free .............. 156.0 41.7 14.2 61.5 38.6 68
Estimated feces from food other I
than bread ................... ........... 6.7 ... ....... ....................
Estimated feces from
bread ............ .................... 35.0 ..........
Total amount digested .................. 38.4 297.8 1,564.5 28.0 11,565
Estimated digestible nutrients i
in bread ...................... .......... 171.0 .......... 1,264.5 .......... .........

Coefficients of digestibility of Per cent. Per cent. Per cent. Per ccit. Per cent. Pe cent.
total food ............................. 90.3 95.5 96.2 42.0 94.4
Estimated coefficients of digest- I
ibility of bread.. ......... .......... 3.0 .......... 95.8 .......... a93.6
Proportion of energy actually I ,
available to body:
In total food ................ .................. .. .. ............................ 90.4.
In bread alone ............ ........... ......... ........ .......... a90.

a Calculated according to the assumption that 90 per cent of the fat in the bread is digestible.








385

During this experiment the subject eliminated 4,486 grams urine,
containing 58.77 grams nitrogen. The nitrogen balance per day was
therefore as follows: Income in food 24 grams; outgo in urine 19.59
ms, and in feces 223 grams, implying a gain of 2.18 grams nitrogen,
responding to 13.6 grams protein.

DIGESTION EXPERIMENT NO. 312.

Kind offood.-Milk, and bread made from finely ground graham
or entire-wheat flour.
Subject.-Man No. 1, as in experiment No. 309.
Weight.-At the beginning of the experiment 163.75 pounds; at the
close 164 pounds.
i Duration.-Three days with nine meals, beginning with breakfast
April 14, 1902.

TABLE 21.-Results of digestion experiment No. 312.


Food consumed:
231 Bread ......................
232 Milk.......................
Total ....................
233 Feces (water free).............
Estimated feces from food other
than bread ..................
Estimated feces from
bread..................
Total amount digested.........
Estimated digestible nutrients
in bread.....................

Coefficients of digestibility of
total food....................
Estimated coefficients of digest-
ibility of bread ..............
Proportion of energy actually
available to body:
In total food...............
In bread alone .............


SWeight
om al
material.


Grains.
3,110.0
9,500.0


260.3


Protein.


Grams.
265.3
315.4
580.7
37.3
9.4


27.9


Fat.


Grams.
31.7
443.6
475.3
13.9


Carbo-
hydrates.

Grams.
1,539. 1
444.6
1,983.7
157.4
A.9


148.5


- I II I


Per cent.


r.....


543.4 461.4 1,826.3
237.4 ........ 1,390.6

Per cent. Per cent. Per calt.
93.6 97.1 92.1
89.5 .......... 90.3


. ........... ......


Heat of
Ash. combus-
tion.

Grams. Calories.
45.4 8,210
73.1 7,723
118.5 15,933
51.7 I 1,130

..........1..........


.......... ..........
66.8 14,803
.......". ..........

Per ce at. Per ccnl.
-56.4 92.9
.......... a 90.2


aCalculated according to the assumption that 90 per cent of the fat in the bread is digestible.

During this experiment the subject eliminated 5,201.7 grams urine,
containing 68.23 grams nitrogen. The total nitrogen balance per day
was therefore as follows: Income in food, 32.34 grams; outgo in urine,
22.74 grams, and in feces, 1.95 grams, implying a gain of 7.65 grams
nitrogen, corresponding to 47.8 grams protein.

DIGESTION EXPERIMENT NO. 313.

SKind offood.-Milk, and bread made from finely ground graham
rentire-wheat flour.
Subject.-Man No. 2, as in experiment No. 310.
SWeight.-At the beginning of the experiment, 164.5 pounds; at the
S164.75 pounds.


-~'--------'--~-' -------'~:~-----








386

Duration.-Three days, with nine meals, beginning with breakfast
April 14, 1902.


TABLE 22.-Results of digestion experiment No. 313.


Food consumed:
S Br ad ............ .......
M ilk.......................
Total ....................
Feces (water free)..............
Estimated feces from food other
than bread................
Estimated feces from
bread..................


Weight
of
material.

Grams.
3,070.0
9,770.0


Protein.


Grams.
261.9
324.4


.. 586.3
294.0 49.3
........... 9.7

.......... 39. 6


Fat.


Grams.
31.3
456.3


Carbo-
hydrates.


Ash.


Grams. Grams.
1,519.3 1 4.8
457.2 75.2


30.3 164.6 49.8
22.8 9.2 .........

7.5 156.4 ..........


Total amount digested .................. 537.0 457.3 1,811.9 70.2
Estimated digestible nutrients I
in bread.............................. 222.3 23.8 1,363.9.......

Coefficients of digestibility of Per cent. Pe'r cen Per cent. Per cernt.
total food .............................. 91.6 93. 8 91.7 58.5
Estimated coefficients of di-
gestibility of bread ................... 84.9 7. 0 89.8 ........
Proportion of energy actually
available to body:
In total food ............... ... ............... ..............
In bread alone ............ .................. ...... ........... ..........
I I


819



14,749


Per eMW.
91.9
87.9

87.7
84.5


During this experiment the subject eliminated 5,201.7 grams urine,
containing 73.35 grams nitrogen. The total nitrogen balance per day
was therefore as follows: Income in food, 32.62 grams; outgo in urine,
24.45 grams, and in feces, 2.60 grams, implying a gain of 5.57 grams
nitrogen, corresponding to 34.8 grams protein.

DIGESTION EXPERIMENT NO. 314.

Kind of food.-Milk. and bread made from finely ground graham
or entire-wheat flour.
Subject.-Man No. 3, as in experiment No. 311.
Weight.-At the beginning of the experiment, 150.5 pounds; at the
close, 151 pounds.
Duration.-Three days, with nine meals, beginning with breakfast
April 14, 1902.

T.ABLE 23.-Results of digestion experiment 'N. 314.


Sample Weight
Sape of Protein.
N- material.


Fat. Carbo- Ash.
hydrates.


Graims. Grams.


Grams. Grams.


Food consumed:
Bread ...................... 2,670.0 227.7 27.2 1,321.4 39.0
Milk..................... 8.000.0 265.6 373.6 374.4 61.6
Total .............................. 493.3 400.8 1,695.8 100.6
Feces (water free .............. 275.0 55.2 11.9 155.4 52.6
Estimated feces from food other
than bread ............................. 8.0 .......... 7.5 ..........
Estimated feces from I
bread ....... ........... ......... 47.2 .......... 147.9 ..........


Sample
No. I


Heat of
tlon.

CaOlmis.
S8,105
7.,lS


487.6 1,976.5 120.0 16,018


231
232


235


Heat of
combus-
tion.


G Orams. Calories.


7,041
6,01%
13,5 "
U<1~


I








37

TABLE 23.-Results qf digestion experiment NVo. 314-Continue l.


aple I Weiht I Car,,- I Heat of
No o. Protein. Fait. ha Ash. combus-
Smaterial. tydrats. tion.

Grami s. G 7ri-, UM. flrl s11,. riruis. (raims. Calories.
Total amount digested ................. 43S. 1 3$8.9 1, 40.4 48.0 12, 409
Estimated digestible nutriments i
in bread ................ ................. 1I ., ............... ..........

Coefficients of digestibility of Per rent. Per r,' nt. Per e*, il. Prr rf u. Prr crnt. Per rt.
total food................................ j .8 97.0 90. 47.7 | 91.6
Estimated coefficients of diges- I|I
tibility of bread ........... .......... 79.3 .......... .. ......... 86.1
Proportion of energy actually
available to body: I I
In total food 87......................... ........................................87.
In bread alone ........... ....... .................... .................... a s2.9

a Calculated according to the assumption that 90 per cent of the fat in the bread is digestible.

During this experiment the subject eliminated 4,115.6 grams urine,
containing 60.91 grams nitrogen. The total nitrogen balance per day
was therefore as follows: Income in food, 27.48 grams; outgo in urine,
20.30 grams, and in feces, 2.94 grams, implying a gain of 4.24 grams
nitrogen, corresponding to 26.5 grams protein.


DIGESTION EXPERIMENT NO. 315.

Kind of food.-Milk, and bread made from straight flour.
Subject.-Man No. 1, as in experiment No. 309.
Weight.-At the beginning and close of the experiment, 166 pounds.
hDuttion.- Four days, with twelve meals, beginning with breakfast
April 28, 1902.

-TABLE 24.-Relt is of digestion experiment No. 315.


Saple Weight
sample of
Na 'material.

Food consumed: Grains.
244 Bread ...................... 3,615.0
243 M ilk ..................... .... 1, ,750.
Total ............ .................


245


CarboI Heat of
Protein. Fat. hCarbo- Ash. combus-
| hydrates. on
tion.

Grains. Gramis. Grams. Grams. CaloriCs.
274.4 13.7 1,976.3 17.7 9,435
351.3 480.6 565.2 90.5 719
625.7 1 94.3 2,541.5 108.2 1, 154


Feces (water free).............. 132.0 29.8 11.3 i 58.1
Estimated feces from foodother i
than bread............................. 10.5 .......... 11.3
Estimated fecesfrom bread .......... 19.3 .......... 16.8
Total amount digested ......... .......... 595.9 483.0 2,483.4
Estimated digestible nutrients '
in bread ......................'.......... 255.1 ...... 1929.5

Coefficients of digestibility of Per cent. Per cent. Per cent. Per cent.
total food............................ .. 95.2 97.7 97.7
Estimated coefficient of diges-
tibility of bread .............. .......... 93.0 .......... 97.6
Proportion of energy actually
available to body:
In total food................. ....... ... ................. ..........
In bread alone ....................... I.......... ..........- ..........


32.8 667


.......... ..........
75. 4 17,487
.......... ..........

Per cent. Per cent.
69.7 96.3
.......... a97.3

.......... 92.2
. .. ...... 93.4


aCalculated according to the assumption that 90 per cent of the fat in the bread is digestible.








38

During this experiment the subject eliminated 7,317.4 grams urine,
containing 87.08 grams nitrogen. The total nitrogen balance per day
was therefore as follows: Income in food, 26.09 grams; outgo in urine,
21.77 grams, and in feces, 1.19 grams, implying a gain of 3.13 grams
nitrogen, corresponding to 19.6 grams protein.

DIGESTION EXPERIMENT NO. 316.

Kind of food.-Milk, and bread made from straight flour.
Subject.-Man No. 2, as in experiment No. 310.
V eight.-At the beginning and close of the experiment, 166 pounds.
SDuration.-Four days, with twelve meals, beginning with breakfast
April 28, 1902.

TABLE 25.-Results of digestion experiment No. 316.

Sample Weight I Carbo- Heat of
Smple of : Protein. Fat. Ash. combu-
Smaterial. hydrates. ion.

Food consumed: Grams. Grams. Grams. T-rams. Grams. Calories.
Bread ..................... 3,480.0 264.1 13.2 1,902.3 17.0 9,082
244 Milk........................ 12,730.0 1 380..620.6 612.3 98.0 9,445
243 --
Total ............................... 644.7 533.8 2,514.6 115.0 18,527
Feces water free).............. 113.0 26.1 14.8 44.0 28.0 583
246 Estimated feces from food other
than bread ................... ........ 11.4 .......... 12.3 ....................
Estimated feces from
bread .................. ......... 14.7 ......... 31.7........
Total amount digested .................... 618.6 519.0 2,470.6 87.0 17,944
Estimated digestible nutrients .
in bread...................... ........ 249.4 1 870.6... .........

Coefficients of digestibility of Per cent. Per cent. Per cent. Per cent. Per cent. Per cet.
total food ................. .............. 95.9 97.2 98.2 75.6 96.9-
Estimated coefficients of di-
ge-tibility of bread........... .......... 94.4 .......... 98.3 .......... a986
Proportion of energy actually
available to body:
In total food.....................'......... ............. ........................ .....92.7
In bread alone .................. ..... ................................. 95.1

a Calculated according to the as.-umption that 90 per cent of the fat in the bread is digestible.

During this experiment the subject' eliminated 6,556.6 grams urine,
containing 92.45 grams nitrogen. The total nitrogen balance per day
was therefore as follows: Income in food, 26.81 grams; outgo in urine,
23.11 grams, and in feces. 1.05 grams, implying a gaifi of 2.65 grams,
nitrogen, corresponding to 16.6 grams protein.

DIGESTION EXPERIMENT NO. 317.

Kind qf.food.-Milk, and bread made from straight flour.
Subject.-Man No. 3, as in experiment No. 311.
Weight.-At the beginning of the experiment, 151 pounds; at the
close, 150.25 pounds.
Duration.-Four days, with twelve meals, beginning with breakfast
April 28, 1902.








39

TABLE 26.-Results of digestion experiment No. 317.


Sample
No.


SWei ht
of
material.


Food consumed:
241 Bread .....................
243 Milk.......................
Total ...................
247 Feces (water free)............
Estimated feces from food other
than bread ..................
Estimated feces from
bread..................
Total amount digested .......
Estimated digestible nutrients
in bread .....................

Coefficients of digestibility of
total food.....................
Estimated coefficientsof digest-
ibility of bread ...............
Proportion of energy actually
available to body:
In total food ...............
In bread alone ...........


Protein. Fat. harb- .
hydratesm.


Ash.


Heat of
combus-
tion.


Grams. Gram. ram. ram. rams. Calories.
3,330. 0 252.7 12.6 1,820.3 16.3 8,691
10,150.0 30 3.5 415.1 488.2 78.2 7,581
......... 556.2 427.7 2,308.5 94.5 16,222
127.0 32.2 19.4 414 34.1 681
........... 9.1 ........... 9.8 ....................

.. ..... 23 1 .... .. 31.6 .... .........
.......... 524.0 408.3 2,267.1 60.4 15,541
.......... 229.6 .......... 1,788.7 '..........)..........

Per cent. Per cent. Per cent. Per cent. Per cent. Per cent.
......... 94.2 95.5 98.2 63.9 95.8
.......... 90.9 .......... 98.2......... a 97.4

.:: : ... ... ............. .. ..............91.8
..... .... .... .... .. ...... ..... .......... 0 94.1


a Calculated according to the assumption that 90 per cent of the fat in the bread is digestible,

During this experiment the subject eliminated 4,747.6 grams urine,
containing 65.99 grams nitrogen. The total nitrogen balance per day
was therefore as follows: Income in food, 23.22 grams; outgo in urine,
16.50 grams, and in feces, 1.29 grams, implying a gain of 5.43 grams
nitrogen, corresponding to 33.9 grams protein.

DIGESTION EXPERIMENT NO. 318.

.Kind offood.-Milk, and bread made from entire-wheat flour.
Subject.-Man No. 1, as in experiment No. 309.
Weight.-At the beginning of the experiment, 167.25 pounds; at the
close, 168 pounds.
Duration.-Four days, with twelve meals, beginning with breakfast
May 5, 1902.

TABLE 27.-Results of digestion e.'periment No. 318.


Sample Weight Carbo- Heat of
ampleNo. of Protein. Fat. hydrates. Ash. combt-
material. tion.
I I --) I.
Food consumed: Gramis. Grams. Granms. Grams. Grams. Calories.
251 Bread ..................... 3,700.0 308.2 40.0 1,913.0 47.0 9.952
258 Milk........................ 12,000.0 360.0 462.0 570.0 87.6 8,820
Total ................... ........ 668.2 .502.0 2.00 2 134.6 18,772
252 Feces (water free).............. 287.0 51.5 15. 161.5 58.8 1,231
Estimated feces from food other
than bread .................. ........ 10.8 .......... 11.4 ....................
Estimated feces from
bread.................. .......... 40.7 ...1501 ....................
Total amount digested ......... .......... 616.7 486.8 2, 321.5 75.8 17,541
Estimated digestible nutrients
in bread...................... ......... 267.5 ......1,76.9 .......... .........


_ __ __ __








40


TABLE 27.-Results of digestion experiment No. 318-Continued.


Sample W
No. material.

Coefficients of digestibility of Per cent.
total food.............. ... ........
Estimated coefficients of digest-
ibility of bread.........................
Proportion of energy actually
available to body: I
In total food..........................
In bread alone........................


Protein. IFat.


Per cent. Per cent.
92.3 97.0
86.8 ..........

.........i...........
.......... ..........


a Calculated according to the assumption that 90 per cent of the fat in the bread is digestible.

During this experiment the subject eliminated 7,889.1 grams urine,
containing 84.41 grams nitrogen. The total nitrogen balance for four
days was therefore as follows: Income in food, 27.92 grams; outgo in
urine, 21.10 grams, and in feces, 2.06 grams, implying a gain of 4.76
grams nitrogen, corresponding to 29.8 grams protein.

DIGESTION EXPERIMENT NO. 319.

Kind of food.-Milk, and bread made from entire-wheat flour.
Subject.-Man No. 2, as in experiment No. 310.
Weight.-At the beginning and close of the experiment, 167.5
pounds.
Duration.-Four days, with twelve meals, beginning with breakfast
May 5, 1902.
TABLE 28.-Results of digestion experiment No. 319.


Weight
of Protein.
material.

Food consumed: Grams. Grams.
Bread .................. 3,655.0 304.5
Milk ....................... 12,380.0 371.4
Total ............................... 675.9
Feces (water free)............. 302.0 i 63.4
Estimated feces from food other
than bread ............................ 11.1
Estimated feces from
bread................ .......... 52.3
Total amount digested ..................I 612.5
Estimated digestible nutrients
in bread........................... 252.2

Coefficients of digestibility of Per cent. Per cent.
total food ........................... 90.6
Estimated coefficients of di-
gestibility of bread........... ......... 82.8
Proportion of energy actually
available to body:
In total food ............... .......... ..........
In bread alone ..................... ..........


Fat.


Grams.
39.5
476.6
516.1
35.2
23.8


Carbo-
hydrates.

Grams.
1,889.5
588.0
2,477.5
140.1


Ash.


Grduu.
46.4
90.4
136.8
63.8


i-
S 11.4 128.3 ........
S 480.9 2, 337.4 73.5
S 28.1 1,761. ..........

Per cent. Per cent. Per cent.
I 93.2 94.3 53.7
71.1 93.2 ..........


.......... .............. ......


During this experiment the subject eliminated 6,910.1 grams urine,
containing 101.58 grams nitrogen. The total nitrogen balance per day
was therefore as follows: Income in food, 28.21 grams; outgo in urine,


Carbo-
hydrates.

Per cent.
93.5
92.2


Ash.


Per cent.
56.8


=............ .. .


Per cant.
"4.4
a91.8

8a93
B o" .
ai.3,9


Sample
No.


251
258


253


Heat of
combus-
tion.

Calories.
9e1.
9,831
9,100
18, 91


11.8 ..........1


981
17,699
8,850

Per cen.
92.9
90.0


___ __


-AA
": ~ ~ if .. '.
.. : : :
.... ... ... %
:.....




r- -;;


41

25.39 grams, and in feces, 2.57 grams, implying a gain of 0.25 gram
nitrogen, corresponding to 1.6 grams protein.

DIGESTION EXPERIMENT NO. 820.

Aind offood.-Milk, and bread made from entire-wheat flour.
Sut edt.-Man No. 3, as in experiment No. 311.
Weight.-At the beginning of the experiment, 150 pounds; at the
close, 151.5 pounds.
Duration.-Four days, with twelve meals, beginning with breakfast
May 5, 1902.

TABLE 29.-Results of digestion e.perimeni No. 320.

e Weiht I Carbo- Heat of
oe hof Protein. I Fat. ra -: h. combus-
No. material. hydrates. tion.

Food consumed: Grams. Gramis. Grams. Grams. Grams. calories.
251 Bread ...................... 3,650.0 304.0 39.4 1,887.1 46.3 9,818
258 Milk....................... 11,750.0 352.5 452.4 558.1 85.8 8,636
Total ............................... 656.5 491.8 2,445.2 132.1 18,454
254 Feaes (water free)........... 262.0 48.9 15.7 135.6 61.7 1,045
Estimated feces from food other'
than bread ................... ..... .... 10.6 .......... 11.2 ....................
Estimated feces from
bread.................... ..... 38.3 124.4 ..................
Total amount digested ......... .......... 607.6 476.1 2,309.6 70.4 i 17,409
Estimated digestible nutrients
in bread................................ 265.7 .......... 1,762.7 ....................

Coefficients of digestibility of Per cent. Per cent. Per cent. Per cent. Per cent. Per cent.
total food .................... 92.5 96.8 94.4 53.3 94.3
Estimated coefficients of di- I
gestibility of bread......................... 87.4 ........ 93.4 .......... a 92.7
Proportion of energy actually
available to body:
In total food ............... .......... ...... ,.... .. ........ .......... 90.2
In bread alone............. .......... ........ .......... ...... .......... a 89.4

a Calculated according to the assumption that 90 per cent of the fat in the bread is digestible.

During this experiment the subject eliminated 5,476.6 grams urine,
containing 88.17 grams nitrogen. The total nitrogen balance per day
was therefore as follows: Income in food, 27.44 grams; outgo in urine,
22.04 grams, and in feces 1.96 grams, implying a gain of 3.44 grams
nitrogen, corresponding to 21.5 grams protein.

DIGESTION EXPERIMENT NO. 321.

Kind of food.-Milk, and bread made from graham flour.
Subject.-Man No. 1, as in experiment No. 309.
Weight.-At the beginning of the experiment, 169.75 pounds; at the
close, 170 pounds.
Duration.-Four days, with twelve meals, beginning with breakfast
S May 16, 1902.




ai


42

TABLE 30.-Results of digestion experiment No. 891.


Weight
material.


Food consumed: -Gramns.
Bread .................... 3,695.0
Milk...................... 11,850.0
Total ..................... ..........
Feces (water free).............. 389.0
Estimated feces from food other
than bread ..........................
Estimated feces from
bread.................... ...
Total amount digested......... ......|
Estimated digestible nutrients
in bread..................... .........

Coefficients of digestibility of Per cent.
total food..............................
Estimated coefficients of diges-
tibility of bread ........ ..........
Proportion of energy actually
available to body:
In total food..........................
In bread alone.............. .........


Protein.


Grams.
308.9
385: 1


Fat.


Grams.
32.2
527.3


Carbo-
hydrates.

Grams.
1,891.8
596. 1


Ash.


Grams.
53.6
91.2


Heat of
combus-
tion.

Calordie.
9,681
9,207


694.0 559.5 2,487.9 144.8 18,888
75.9 25.1 222.0 66.1 1,641
11.6 .......... 11.9 ....................

64.3 .......... 210.1 .......... .........
618.1 534.4 2.265.9 78.7 17,247
244.6 .......... 1,681.7 ........... ........


Per cent. Per cent.
89.1 95.5
79.2 ..........


.......... ..........


Per cent.
91.1
88.9


Per cent.
51.4


Per cent.
91.3
085.8

87.2
a82.7


a Calculated according to the assumption that 90 per cent of the fat in the bread is digestible.

During this experiment the subject eliminated 5,211 grams urine,
containing 73.48 grams nitrogen. The total nitrogen balance per day
was therefore as follows: Income in food, 28.95 grams; outgo in urine,
18.37 grams, and in feces, 3.04 grams, implying a gain of 7.54 grams
nitrogen, corresponding to 47.1 grams protein.


DIGESTION EXPERhIMENT NO. 322.

Kind offood.-Milk, and bread made from graham flour.
Subject.-Man No. 2, as in experiment No. 310.
Weight.-At the beginning and close of the experiment, 166.5
pounds.
Duration.-Four days, with twelve meals, beginning with break-
fast May 16, 190).

TABLE 31.-Results of digestion experiment No. 322.


Food consumed:
Bread ...................
M ilk.......................
Total...................
Feces (water fcee).............
Estimated feces from food other
than bread................
Estimated feces from
bread..................
Total amount digested.........
Estimated digestible nutrients
in bread.................


Weight
of
material.

Grams.
3,455.0
11,750.0
..........


Protein.


Grams.
288.8
381.9
670. 7


Fat.


Grams.
30.1
522. 9
553.0


Carbo-
hydrates.

Grams.
1,768.9
591.0
2,359.9


-Ash.


Grams.
50.1
90.5
140.6


Heat of
combus-
tion.

Calories.
9,052
9,130
18,182


387.0 69.1 54.1 197.9 65.9 1,730
.......... 11.5 26.1 11.8 .......... 361

.......... 57.6 28.0 186.1 .......... 1,369


601.6
231.2


498.9


2.1


2,162.0
1,582.8


74.7


16,452
7,683


Sample
Nt'.


Sample
No.


260
259


262








43

TABLE 31.-Results of digestion experiment Ao. 3.9 --Continued.


Sample Wei ht
No material.
|


Protein.


Carbo- Hieat of
Fat. hCarbas Ash. combus-
hydrates tion.


Coefficients of digestibility of Percent. Per cent. Per cent. Per cent. Per ceit. Per cent.
total food............. ............ .. .... 89.7 90.2 91.6 53.1 90.5
Estimated coefficients of digest-
ibility of bread ............... ..........' .1 7.0 89., .......... 84.9
Proportion of energy actually
available to body: '
In total food ...................................... ..............................86.3
In btead alone .. ........... ..... ....... ........ .. ..........:.......... 81.7


During this experiment the subject eliminated 4,532 grams urine,
containing 52.57 grams nitrogen. The total nitrogen balance per day
was therefore as follows: Income in food, 27.94 grams; outgo in urine,
13.14 grams, and in feces, 2.76 grams, implying a gain of 12.04 grams
nitrogen, corresponding to 75.2 grams protein.

DIGESTION EXPERIMENT NO. 323.

Kind qoffood.-Milk, and bread made from graham flour.
Subject.-Man No. 3, as in experiment No. 311.
Weight.-At the beginning of the experiment, 151.25 pounds: at
the close, 150.5 pounds.
Duration.-Four days, with twelve meals, beginning with breakfast
May 16, 1902.


TABLE 32.-Results of digestion experiment No. 323.


Sample
No.


260
259


263


Weight i Carbo- Heat of
of Protein. Fat. hydrates. A, h. combus-
material. tion.

Food consumed: Gramns. Gramns. Grams. Granis. Graoins. Calories.
Bread ...................... 3, 580.0 299.3 31.1 1,832.9 51.9 9,379
Milk....................... 11,000.0 357.5 489.5 553.3 84.7 8.-46
Total ...................... ......... 656.8 520.6 2.386.2 136.6 17,925
Feces (water free).............. 384.0 73.4 31.7 202.3 76.6 1,601
Estimated feces from food other
than bread ................... .......... 10.7 24.5 11.1 .......... 34
Estimated feces from


bread..................
Total amount digested .......
Estimated digestible nutrients
in bread.....................

Coefficients of digestibility of
total food..... ...........
Estimated coefficients of diges-
tibility of bread ..............
Proportion of energy actually
available to body:
In total food...............
In bread alone.............


.......... 62.7 7.2 191.2 .......... 1,253
.......... 53.4 4t8.9 2., 3.9 6. 0 16,324
.......... 236.6 23.9 1,641.7 .......... 8,126

Per cent. Per cent. Per cent. Per cent. Per cent. Per cent.
......... 88 93.9 91.5 43.9 91.1
.......... 79.0 76.8 89.6 1......... 86.6


............I


87.0
83.5


During this experiment the subject eliminated 4,509 grams urine,
containing 85.16 grams nitrogen. The total nitrogen balance per day
was therefore as follows: Income in food, 27.42 grams; outgo in


I


I-


-1


::::::::::(:::::::::I::::::::::1:::::: ::::
.......... .. . .. ..
.......... ......... ... ..........








44

urine, 21.29 grams, and in feces, 2.94 grams, implying a gain of .3.19
grams nitrogen, corresponding to 19.9 grams protein.

SUMMARY OF RESULTS OBTAINED WITH SOFT WINTER WHEAT
PRODUCTS.

In Table 33 a summary is given of the digestibility of the nutrients,
and availability of the energy of the entire food of the various digestion
experiments with milk and white bread from mixed-grade flour, white
bread from straight-grade flour, entire-wheat bread, and graham, all
ground from soft winter wheat.

TABLE 33.-S'ummary of digestion experiments with soft winter wheat; digestibility of
nutrients and availability of energy of total food.

ExpriN- Sb e Kind of food. Protein. Fat. h. Energy.


Experiments with Indiana wheat: Per cent. Per cent. Per cent. Per cent.
309 1 Milk and white bread (mixed grade... 95.8 93.7 96.2 90.4
310 2 ....do ............... .................. 93.4 93.5 96.9 90.3
311 3 ....do .................................. 90.3 95.S 96.2 90.4
Averageof 3...................... 93.2 94.2 96.4 90.4


312 1 Milk and entire-wheat bread...........
313 2 ....do ......... ................. .......
314 3 ....do .................................
Average of 3...................
Experiments with Michigan wheat:
315 1 Milk and white bread (standard patent)
316 2 ....do...............................
317 3 ....do .............................
Average of 3......................
318 1 Milk and entire-wheat bread...........
319 2 ....do............................
320 3 ....do ............... ..................
Average of 3 .............. ....
321 1 Milk and graham bread ................
322 2 ....do ............................
323 3 ....do .............................


93.6 97.1 92.1 8S.6
91.6 93.8 91.7 87.7
88.8 97.0 90.8 87.5
91.3 96.0 91.5 87.9

95.2 97.7 97.7 92.2
95.9 97.2 98.2 92.7
94.'2 95.5 98.2 91.8
95.1 96.81 98.0 92.2
92.3 97.0 98.5 89.3
90.6 93.2 94.3 88.9
92.5 96.8 94.4 90.2
91.8 95.7 94.1 89.5
89.1 95.5 91.1 87.2
89.7 90.2 91.6 86.2
88.8 93.9 91.5 87.0


Average of 3...................... 89.2 93.2 91.4 86.8


The results summarized in the table show that, in general, the ration
consisting of milk and white bread made from the patent grade flour
was more digestible than the rations of milk and bread made from
either of the other kinds of flour, also that a larger percentage of
energy was available to the body in the case of white bread and milk
than from the entire-wheat or graham bread and milk.
In the experiments with Indiana soft wheat individual differences as
regards the ability to digest the bread and milk rations were quite
pronounced with the various subjects; in the case of the white bread, a
difference of about 5.5 per cent in the digestibility of the protein being
observed. Subject No. 1 digested the wheat bread and also the entirie-
wheat bread more completely than did subject No. 2 or No. 3. With








45


each subject, however, the digestibility of the ration with white bread
was greater than that with entire wheat. In the experiments with
Michigan soft wheat individual differences are noticeable, but they
are less pronounced, and, as was the case with the other wheats, each
subject digested the ration of white bread and milk more completely
than bread made from either of the other flours.
SIn Table 34 the calculated digestibility of the nutrients and availa-
bility of the energy of the bread alone are given:

TABLE 34.-Summary of digestion experiments with soft winter wheat; digestibility of
nutrients and availability of energy of bread almoe.


Kind of food.


Experiments with Indiana wheat:
White bread (mixed grade flour) ..............
....do .................. ..........................
....do ..................................
SAverage of 3 ......... ................. ...
Entire-wheat bread .............................
....do. ............................................
....do .............................................
Average of 3 .................................
Experiments with Michigan wheat:
White bread (standard patent)...................
....do .............................................
....do .............................................
Average of 3-................................


Protein. hydrates. Energy.


Per cent.
94.2
89.4
83.0
88.9
89.5
84.9
79.3
84.6

93.0
94.4
90.9
92.8


Entire-wheat bread ............................. 86.8
....do ............................................. U 8
....do .... ....................... ............ .... 87.4
Average of 3 ......... ................ ..... 85.7
Graham bread.................................... 79.2
....do ................................ ............ 80.1
....do ............................................. 79.0
Average of 3................................ 79.4


Per cent. Per cent.
95.6 90.4
96.6 90.4
95.8 90.4
96.0 90.4
90.3 85.2
89.8 84.5
88. 8 82.9
89.6 84.2

97.6 93.4
9. 3 95.1
98.2 94.1
98.0 94.2
92.2 87.9
93.2 86.8
93.4 89.4
92.9 88. 0
88.9 82.7
89.5 81.7
89.6 83.5
89.3 82.6


These results are calculated, as explained on page 19. by assuming
that 97 per cent of the protein and 98 per cent of the carbohydrates of
the milk were digested."
The average result of the experiments with flour milled from Indi-
ana soft winter wheat shows that 88.9 per cent of the protein and 96
per cent of the carbohydrates of the white bread from mixed-grade
flour were digested, and that 90.4 per cent of the energy was available.
As regards the bread from entire-wheat flour, ground from the same
lot of wheat, 84.6 per cent of the protein and 89.6 per cent of the car-

a It was also assumed that 95 per cent of the fat of the milk would be digested, but
with this factor the digestibility of the fat of bread could be computed satisfactorily
in only a few cases; therefore figures for this constituent are left out of Table 34.
In all cases where the digestibility of bread fat could not be computed it was assumed,
in order to estimate the available energy of the bread, that 90 per cent would be
digested.


Subject
No.


Experi-
ment
No.


809
810
811


312
8183
814



815
316
317


318
319
320


321
322
323


-i






46

bohydrates were found to be digestible, and 84.2 per cent of the energy
to be available. It will be observed, further, that with each of the sub-
jects the nutrients of the white bread were more digestible and the
energy more available than was the case with the entire-wheat bread.
The white bread made from straight-grade flour milled from Michi-
gan soft winter wheat had the highest digestibility of any of the sam-
ples ground from this variety, namely, 92.8 per cent of the protein
and 98 per cent of the carbohydrates, while 94.2 per cent of the energy
was available to the body. Of the protein of bread from the entire-
wheat flour milled from the same lot of wheat, 85.7 per cent, and of
the carbohydrates 92.9 per cent were digestible, 88 per cent of the
energy being available to the body. The lowest coefficients of digesti-
bility were found in the graham bread, the values being 79.4 per cent
for the protein, 89.3 per cent for the carbohydrates, and 82.6 per cent
for the energy available to the body. As will be seen, there was a dif-
ference of 13.4 per cent in the average digestibility of the protein of
the graham bread and white bread made of flour from the same lot
of wheat, while 8.7 per cent less of the carbohydrates of the graham
bread was digestible, and 11.6 per cent less of the energy was avail-
able. As in the case of the entire ration, differences attributable to
individuality are noticeable, which are, however, not great enough to
invalidate the general deduction that white bread is the most digesti-
ble, graham bread the least, and entire-wheat bread intermediate
between them.
Table 35 gives a summary of the experiments on the basis of the pro-
portion of total and digestible nutrients and available energy in the
different grades of flour as milled from soft winter wheat:

TABLE 35.-Proportion of total and digestible nutrients and available energy in different
grades of soft winter-wheatflour as milled..

Protein. Carbohydrates. Heat of combus-
Num- tion per gram.
ber of Grade of flour.
sample Total. De- Total. Dest- Total. ab
ible. ible. able.
Per cent. Per cent. Per cent. Per cent. (Ctories. C ories.
221 Mixed-grade flour.............. 12.30 10.93 75.94 72.90 4.010 3.645
219 Entire-wheat flour............. 12.80 10.82 74.40 66.66 4.020 3.384
240 Straight white flour............ 10.92 10.13 77.15 75.61 3.799 3.579
241 Entire-wheat flo:r ............. 12.01 10.29 74.17 68.80 3.860 3.399
242 Graham flour.................. 12.24 9.72 73.27 65.43 3.906 3.226

The digestible nutrients were obtained by multiplying the percent-
age of the total nutrients by the average digestion coefficients given
in Table 34. The mixed-grade flour, for example, contained 12.3 per
cent total protein, which was found to be 88.9 per cent digestible,
being therefore equivalent to 10.93 per cent of digestible protein.
The mixed-grade flour prepared from the Indiana wheat contained
10.93 per cent digestible protein, 72.90 per cent digestible carbo-






47


hydrates, and 1 gram of the flour yielded 3.645 calories of available
energy. The entire-wheat flour prepared from the same wheat yielded
10.82 per cent digestible 'protein, 66.87 per cent digestible carbo-
hydrates, and 3.375 available calories per gram. The difference in
digestible protein is small, being 0.11 per cent in favor of the mixed-
grade flour. The difference in the digestible carbohydrates is quite
large, being 6.24 per cent in favor of the mixed-grade flour. The
difference in the available energy is also large, amounting to 0.261
calorie per gram in favor of the white flour.
While there is no material difference as to the amount of digestible
protein in the two kinds of flour, the differences in digestible carbo-
hydrates and available energy are decidedly in favor of the mixed-grade
flour. The entire-wheat flour contained a larger amount of protein,
but, as shown in Table 34, this protein is less digestible than that of
the mixed-grade flour, which was more finely granulated.
The straight-grade flour prepared from the Michigan wheat con-
tained 10.13 per cent digestible protein, 75.61 per cent digestible
carbohydrates, and 3.574 calories of available energy per gram. Com-
pared with graham flour, this shows 0.4 per cent of digestible protein,
10.18 per cent of digestible carbohydrates, and 0.353 calorie of avail-
able energy per gram in favor of the white flour. Compared with
the entire-wheat flour, the results show a difference of 6.81 per cent.
digestible carbohydrates and 0.180 available energy per gram in favor
of the straight-grade flour; the difference in digestible protein, though
too small to be of significance, is 0.16 per cent in favor of the entire-
wheat flour. In the description of the samples it was stated that the
straight-grade flour did not contain all of the granular middlings
which are usually included in the preparation of ordinary straight
flours. Had the flour contained the granular middlings, the percent-
age of protein, it seems fair to conclude, would have been higher than
10.92. While the difference in total protein is 1.1 per cent in favor of
the entire-wheat flour, the higher degree of digestibility of this con-
stituent in the straight-grade flour makes the figures for the total
digestible protein in the two kinds of flour practically the same.
Hence, what is gained from the somewhat larger amount of protein in
the entire-wheat and graham flours is lost in digestibility. While the
difference between the digestible protein in the straight-grade and
entire-wheat flours prepared from the same lot of soft wheat is small,
the difference in digestible carbohydrates is large, being 6.8 per cent
in favor of the white flour. Since a larger amount of digestible carbo-
hydrates and available energy is secured from the mixed and straight-
grade flours than from the entire-wheat flour and no appreciable
differences were observed as to digestible protein, it would appear
that a larger total amount of nutrients and energy is available to the







48

body from the straight than from the entire-wheat or graham floum:rs
a conclusion in accord with the results of all our former work.
That the lower degree of digestibility of the entire-wheat and graham "'
flours was probably due at least in part to a coarser granulation h
of the particles, which consequently exposed a relatively smaller
amount of surface to the action of the digestive fluids, was shown by a
microscopical examination of the feces. The feces from both the"
entire-wheat and the graham flours under the microscope showed a
larger proportion of starch particles that had not been acted upon in
the digestive tract than the feces from standard patent flour. The
micro-photographs reproduced (Pls. I-III) show the fineness of division
of the three sorts of flour and the starch granules in the feces obtained-
from the standard patent, the entire-wheat, and the graham flours,
prepared by grinding in a mortar.
These deductions are in accord with the results of numerous micro-
scopical studies of the feces from different sortsof wheat products, and
in this connection it is interesting to refer to some of these and closely
related investigations. Among others may be mentioned the work of
Rubner, Pappenheim, b Constantinidi,c and Raudnitz. d
In general it may be said that these investigators found that.starch
was very thoroughly digested, but that the cells making up the outer
portion of the wheat berry were little attacked by the digestive juices,
and hence the contents of such cells were not assimilated. Rubner
pointed out that the amount of undigested nitrogen increased with an
increase in the amount of the outer portion of the grain retained in
flour in milling. Rathayv reports experimental studies, of which he
himself was the subject, in which the diet for a week consisted of :
graham bread and tea. The bread was made without leaven or yeast..'
The feces from the fifth and seventh day were examined microscop- .
ically. He found that the grain portions which had been little masti-
cated were softened, but almost entirely undigested. From only a
few of the outer cells of the endosperm had the starch grains and the
proteid materials disappeared, while the greater part of these nutri-
ents was excreted unchanged. The general conclusion from his inves-
tigations was that the greater portion of the feces consisted of undi-
gested residues of wheat bran in the form of large flakes composed
of the seed coats and aleurone layer. The latter leaves the intestines
unchanged, probably because the thick walls of the aleurone cells pre-
vent the action of digestive juices upon the cell contents. So far as
can be learned, this investigation was the first which at all satisfac-

a Ztschr. Biol., 15 (1879), p. 115.
bLehrbuch der Miillerei (1890), 3d ed., cited by Moeller.
cZtschr. Biol., 23 (1887), p. 447.
d Prag. med. Wchnschr., 7 (1892), pp. 1, 13.
eJahresber. K. K. Realschule Sechshaus, Wien, 1874, cited by Moeller.







U. S. Dept. of Agr., Bul. 126, Office of Expt. Stations


PLATE I.


FIG. 1.-FLOUR PARTICLES FROM STRAIGHT PATENT FLOUR NO. 240 (MAGNIFIED 15
DIAMETERS).


FIG. 2.-FLOUR PARTICLES FROM ENTIRE-WHEAT FLOUR NO. 241 (MAGNIFIED 15
DIAMETERS).









4
4



































A*








U. S. Dept of Agr., Bul. 126, Office of Expt. Stations


FIG. 1.-FLOUR PARTICLES FROM GRAHAM FLOUR No. 243 (MAGNIFIED 15 DIAMETERS).


FIG. 2.-FECES FROM BREAD MADE FROM STRAIGHT PATENT FLOUR (MAGNIFIED 15
DIAMETERS).


PLATE II.












I






4
i




I





















*q







U. S. Dept. of Agr., Bul. 126 Office of Expt Statioins


FIG. 1.-FECES FROM BREAD MADE FROM GRAHAM FLOUR (MAGNIFIED 15 DIAMETERS).


FIG. 2.-FECES FROM BREAD MADE FROM ENTIRE-WHEAT FLOUR I MAGNIFIED 15
DIAMETERS).


PLATE III.











































































































li

































. 1







49


torily opposed Liebig's idea of the high value of the gluten layer of
wheat.
Perhaps the most extended study of vegetable residues occurring
in feces was made by Moeller". In some of the experiments the
diet consisted of coarse bread with butter and cheese; white bread,
rice, and butter; bread, and porridge made of wheat grits and milk;
Sbead, and porridge made from milk and flour; oat preparations,
namely, oat grits, oat flake, soup, and oat cocoa; rye bread and various
mixed diets, or diets in which potatoes or legumes predominated.
SPortions of feces were repeatedly washed with water and then exam-
ined under the microscope. The conclusion was reached that healthy
individuals digested the starch of cereals and potatoes almost completely,
even when the starchy foods were not in favorable mechanical condition,
as is the case in bran from cereals, in rice, or in sliced potatoes; and fur-
ther, that the soft cell walls of the starch cells are also digested. The
aleurone layer of cereals in which the cell membranes consist of pure
cellulose was not digested, nor were the protein and fat which form
the contents of the cells digested unless the cell walls had been mechan-
ically ruptured. The cells making up the germ were not digested or
ruptured by the action of the digestive juices. The author believes
that these experiments warrant the conclusion that fine flour is prefer-
able to coarse flour. Comparative experiments with coarse flour and
the same flour after passing through the intestinal tract, lead the
author to the conclusion that the cell walls almost absolutely shield
the cell contents of the aleurone layer from the action of the digestive
juices, and he concludes that cereal brans should be regarded as indi-
gestible. The outer layer of the cereal grains, including endosperm
cells with their starch content, was also found to be undigested.
Laboratory experiments indicated that cellulose which had not ligni-
fled was little attacked by digestive juices, the amount being inversely
proportional to the thickness of the cell membrane. On the other
hand, the middle lamelle were readily disintegrated by digestive juices.
Tests with laboratory reagents also showed that the inner side of the
gluten cells was most resistant but after a time softened, and this indi-
cates that possibly gluten cells may become softened in the intestine
and then digested. That this occurs very seldom is indicated by the
large number of unchanged cells found in the feces.
As noted above, in connection with the experiments reported in
this bulletin, a microscopical examination of the feces showed that
in those from the graham and entire-wheat breads made from flour
ground from the same lot of soft wheat, a much larger number of
unaltered starch granules were present, and the particles had not been
as completely acted upon by the digestive fluids as in the case of the
straight-grade-flour bread.
a Ztschr. Biol., 35 (1897), p. 291.
19047-No. 126-03- 4







50


Summarizing briefly the results of the fifteen experiments with soft. .iZ
wheat flours, it appears that while the graham and entire-wheat flours
contain a larger amount of protein and energy, the lower degree'of I
digestibility of these flours, due to the coarser granulation, renders
available to the body a smaller proportion of total nutrients as well as
energy than in the case of straight-grade flours, ground from the same
wheat, which are more finely granulated and more completely digested.
This is entirely in accord with the results obtained in the investiga-
tions with hard-wheat flours more exhaustively milled.
As was the case in the tests with bread from different grades of hard.
wheat flour, no variations were observed in the metabolism of nitrogen
which could be attributed to the use of the different sorts of flour
constituting the principal part of the diet.

GENERAL SUMMARY OF RESULTS AND CONCLUSIONS.

The experiments with hard wheat milling products reported in the
present bulletin are the latest of a fairly extended series which has
given uniform results. The experiments with soft wheat are the first
of a proposed series and are less numerous than those made with hard
wheat. The results already obtained, however, are in accord with
what has been learned regarding the milling products of hard wheat.
Some general deductions from the experiments as a whole seem
warranted.
As shown by analysis the patent flour, ground from the hard and
soft wheats studied, had a somewhat lower protein content than the
graham flour and entire-wheat flour ground from the same wheats, but ..
according to the results of digestion experiments with the different ':I
grades of flour from these wheats, the proportion of digestible pro-
tein and the available energy in the patent flour was larger than in
the coarser grades. The lower digestibility of the protein in the latter
is, it appears, due to the fact that in these grades a considerable por-
tion of this constituent is contained in the coarser particles (bran) and :
thus escapes digestion as it is not acted upon by the digestive juices.
Thus, while there may be actually more protein in a given.amount of
graham or entire-wheat flour than in an equal amount of patent flour
ground from the same wheat, the body secures less of the protein and
energy from the coarse flour than it does from the fine, since although'
the retention of the bran and germ increases the percentage of pro
tein it decreases the digestibility. By digestibility is meant the dif- .:
ference between the amounts of the several nutrients consumed andi
the amounts excreted in the feces. No attempt was made to study th
ease or rapidity of digestion of the different sorts of flour. When th.
digestibility of different grades of patent flour was studied it
found that there was no marked difference between standard pated







51


flour and the other grades in this respect. The digestibility of all
these flours was found to be high, apparently owing largely to their
mechanical condition, that is, owing to the fact that they were finely
ground.
Microscopical studies of the feces from bread made from the different
grades of flour indicate that the superior digestibility of patent-flour
bread is due to the fineness of division of the flour particles and also to
the fact that the cell walls of the material making up the interior of
the wheat berry are less resistant to digestive juices than the walls of
the cells making up the outer layers of the grain. In other words, the
patent flour is superior as regards digestibility, on account of both its
mechanical condition and its physical properties.
In discussions of the comparative value of fine wheat flour and the
coarser grades, it is often claimed that the larger proportion of mineral
matter, and especially phosphorous compounds, in whole-wheat and
graham flours is a. reason for preferring them to patent flour. In this
case also it is undoubtedly true that the proportion of mineral con-
stituents which is digestible, or, in other words, which the body can
retain, from the different sorts of flour, must be considered, as
well as the amounts which chemical analysis shows to be present in
the food. In view of the fact that there is apparently no satisfac-
tory method for determiining the proportion of ash in the feces,
derived from metabolic products, and that it is, therefore, impossible
by present methods to determine the true digestibility of the mineral
constituents, no values for the digestibility of ash have been included
in the present bulletin. It may be noted in this connection that
it is a well-recognized fact that when the coarser milling products
are fed to cattle no great amount of phosphorus (one of the most
important manurial elements) is retained in the animal body. This may
possibly be an indication that the phosphorus, even if present in con-
siderable amounts in the feed, is not in a form which can be assimilated
by animals. This is, however, little more than conjecture, and more
experiments with man and the lower animals are needed before satis-
factory conclusions can be drawn.
Briefly stated, the most important deductions from the results of
these investigations with hard and soft wheat are in accord with the
conclusions drawn from the earlier investigations of this series. The
nutritive value of flour, in so far as the quantities of digestible protein,
fats, and carbohydrates, and available energy are concerned, is not
increased by milling the wheat in such a way as to retain a large pro-
portion of bran and germ. The differences in the amounts of total
nutrients furnished the body by the various grades of flour are, how-
ever, relatively small, all grades being quite thoroughly digested.
The coarser flours have a tendency to increase peristaltic action, and
are on this account especially valuable for some persons. Judged by







52.

composition and digestibility, all the flours are very nutritious fo
which experience has shown are wholesome as well. When also the
fact is taken into account that they furnish nutritive material in an
economical form, their importance is evident. The fact must not be,
lost sight of that using different grades of flour for bread making and
other household purposes offers a convenient method of adding to the
variety of the daily diet, a matter'which is of undoubted important ce

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