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BULLETIN No. 717 ¢
NY
Contribution from the States Relations Service
A. C. TRUE, Director
Washington, D. C. PROFESSIONAL PAPER September 25, 1918
DIGESTIBILITY OF PROTEIN SUPPLIED BY SOY-
BEAN AND PEANUT PRESS-CAKE FLOURS.'
By Artur D. Hoimes, Specialist in Charge of .Digestion Experiments, Office of Home
Economics.
CONTENTS.
Page Page
Introduction @225¢.-4-ceee ee Pr lpn <8 1 | The subjects of the digestion experiments.... 14
Investigations of digestibility of common Preparation of experimental diets............ 14
Le puimesh ose oacysicis wemtere = oicis)siarsjdevereis's wicieiais 2 | Details of the experiments. ......:.......--.- 15
Source and available supply of soy-bean and The digestibility of protein supplied by soy-
peanut pressicakesS! 225 25.22 ae veins cine ne 3 bean press-cake flour....................-- 16
Factors considered in determining food The digestibility of protein supplied by pea-
VAIUG Ola PlOLell ness <ion celine anise cles sei 4 nut press-cake fowrs2: 2c. asses cece see 19
The amino acids supplied by soy-bean and Experiments with flour made from roasted
peanut proteins as compared with those Peanuts 325). Skee cheese. sepiseaee eer 20
supplied by common cereal proteins....... 5 | Experiments with flour made from raw pea-
Biologic value of soy-bean and peanut pro- TUES Se et ae ees S ene ei acer aeeees 22
teins as compared with that of common Summary of all experiments with peanut
Cereal proteins sso) eed cae cuca -aajee'e 8 Rourss.272 aiesc ec eewsee un be Semeetiesee 23
Digestibility of soy-bean and peanut pro- General conclusions regarding the value of
GOUT Beets eect Ns area no cic ate ee wrciatbto ays ote 12 soy bean and peanut flours as food......... 25
Preparation of soy-bean and peanut press-
Cakes flonrssacroc tee wocs eeenmava sense eee ke 12
INTRODUCTION.
It has long been recognized that in order to maintain the well-
being of an individual, or in fact to maintain the normal body proc-
esses, proteins of sufficient quantity and quality are absolutely
essential. The proteins normally occurring in the human dietary
are of a quite varied nature and are derived from both the animal
and vegetable kingdoms. Those foods which contain the largest
proportion of protein and are ordinarily referred to as protein-rich
foods are obtained largely from the animal kingdom and include
such food materials as meats, eggs, and milk.
1 Prepared under the direction of C. F. Langworthy, Chief, Office of Home Economics.
Norte.—This bulletin records studies of the digestibility of protein supplied by soy-bean and peanut
press-cake flours. It is primarily of interest to students and investigators of food problems.
64347°—18—Bull. 717-——1
ae BULLETIN 717, U. S. DEPARTMENT OF AGRICULTURE.
The many studies which have been made to determine the actual
importance for dietary purposes of the proteins supplied by meats,
eggs, and milk show quite conclusively that these proteins are of
high biologic value. Unfortunately the supply of these food mate-
rials is becoming constantly less adequate to meet the needs of the
very rapidly increasing population of this country. Furthermore,
these foods are relatively expensive, and consequently can not be
eaten as freely as formerly by those of small incomes. As a result of
these conditions, students of nutrition have given considerable
attention to the possibility of replacing animal proteins with vege-
table proteins, and as a consequence the demand for vegetable foods
which supply proteins that are of value for human food is steadily
increasing. The cereals which contain relatively small amounts of
protein are already so extensively used that as a group they now
supply nearly one-half of the total protein of the average American
diet. While practically all of the common vegetable foods contain
protein, the amount present in foods of vegetable origin is small except
in the case of the legumes, which may be classed as protein-rich food.
Accordingly it appears that a more extensive use of legumes as a
source of protein is to be desired. Those legumes most commonly used
in this country are the well-known navy beans, red kidney, and lima
beans, the garden pea, frijoles, pinto beans, and several varieties of
cowpeas. Many studies have been made of the nutritive value and
possible uses of these legumes, and several investigators have con-
ducted experiments to determine their digestibility.
INVESTIGATIONS OF DIGESTIBILITY OF COMMON LEGUMES.
The digestibility of hulled peas cooked thoroughly until soft and
passed through a sieve was determined by Rubner,! who found that
the protein was 72 per cent digested. In a second experiment in
which the subject ate 600 orate of peas per day the digestibility was
found to be 83 per cent.
Malfatti ? determined the digestibility of the protein supplied by a
porridge made of split peas and found it to be 86 per cent digested.
Richter * reported that in an experiment in which the subject con-
sumed 600 grams of purée of pea the protein was 90 per cent
digested.
Snyder‘ conducted three experiments to determine the digesti-
bility of pea protein. and served a porridge (containing 82 per cent
of water) made from dried peas. The porridge was eaten in conjunc-
tion with a basal ration consisting of rice, milk, and sugar; one-
third of the protein of the diet was supplied by the peas. He found
that the average digestibility of the pea protein was 80 per cent.
1Ztschr. Biol., 16(1880), No. 1, pp. 119-128, 3 Arch. Hyg., 46 (1903), No. 3, pp. 264-273.
2 Jahresber, Tier-Chem., 15 (1885), p, 412, 4 Minnesota Sta. Bul. 92 (1905), pp. 267-270.
DIGESTIBILITY OF SOY-BEAN AND PEANUT FLOURS. 3
Prausnitz! in a study of the digestibility of white beans cooked in
salted water until soft found that the protein was approximately 70
per cent digested.
Snyder? studied tne digestibility of navy beans which were prepared
by cooking for 20 minutes in boiling water containing bicarbonate
of soda, removing the skins, and baking the hulled beans in the
usual way. The results of three experiments indicated that bean
protein was 80 per cent utilized.
Woods and Mansfield,’ in a study of the digestibility of rations for
lumbermen, included three experiments in which the ration contained
beans, and found that the digestibility of the protein of the total diet
was 85 per cent, and estimated that the digestibility of the bean
protein was 78 per cent.
Wait + conducted a series of 72 experiments to determine the
digestibility of kidney beans, white beans, and three varieties of
cowpeas eaten in conjunction with a basal ration consisting of bread,
milk, butter, pork, bananas, and sugar, and found that the coeffi-
cients of digestibility of the proteins were as follows: Kidney beans
77 per cent, white beans 78 per cent, Whippoorwill cowpeas 70 per
cent, Clay cowpeas 74 per cent, and Lady cowpeas 83 per cent.
The general conclusion to be drawn from the experimental data
cited above is that while the proteins of the more widely used legumes
are quite well utilized by the human body, comparing very favorably
in this respect with the cereal proteins, they are not as completely
utilized as the proteins supplied by such animal! foods as meats, eggs,
and milk.
SOURCE AND AVAILABLE SUPPLY OF SOY-BEAN AND PEANUT PRESS
CAKE.
Considerable interest has recently been aroused regarding the
nutritive value of two legumes, soy beans, which as yet have not been
extensively used in this country for food purposes, and peanuts,
which, though well known and commonly eaten, have been used as a
casual rather than a staple article of diet. It is of course true that
soy beans have found limited use in some localities and that peanuts
have been quite extensively used as a constituent of confectionery,
as ‘‘salted peanuts,’ and more recently as ‘‘peanut butter,’ but
neither has been very extensively used in the manner in which peas
and beans appear in the dietary.
During very recent years the production of both these legumes
has grown many fold. The increase in the culture of peanuts is due
very likely to the fact that the boll weevil has made the growing of
1Ztschr. Biol., 26 (1890), pp. 227-232.
2 Minnesota Sta. Bul. 74 (1902), p. 122.
3U.S. Dept. Agr., Office Expt. Stas. Bul. 149 (1904), pp. 60, pls. 4.
4U.S. Dept. Agr., Office Expt. Stas. Bul. 187 (1907), pp. 55.
4 BULLETIN 717, U. S. DEPARTMENT OF AGRICULTURE.
cotton unprofitable in many sections of the South and peanuts are
now grown.as a supplementary crop. The recent increase in the
production of soy beans has probably resulted primarily from the
present great need of additional food materials for both human and
animal consumption.
The present imperative demand for oils in the manufacture of
explosives, coupled with the increased demand for oils for industrial
and edible purposes, makes it highly probable that large quantities of
soy beans and peanuts will be pressed in cottonseed-oil mills where the
machinery is adapted for the expression of oil from these oil-bearing
seeds as well as cotton seed.
It has been estimated that 150,000 eee or 9,000,000 pounds
of soy beans was pressed Inne the season (1917- 18) in North
Carolina alone, which produced more than 3,500 tons of press cake.
In addition to the supply of domestic soy beans there are large
quantities of beans which have been imported from other coun-
tries. It is also reported? that the greater portion of the present
unusually large crop of peanuts will be pressed. The residue, which
remains after most of the oil has been removed from soy beans
and peanuts, commercially known as press cake, contains a high
percentage of protemm. Such press cake has been very largely used
as stock feed and, because of its high nitrogen content, for fer-
tilizing purposes. It is at once apparent, however, that if care
were exercised in grading and cleaning sound soy beans and in shelling
and sorting sound peanuts, and if they were pressed under sanitary
conditions, the resulting press cakes should be of considerable value
for use as human food, and especially as a source of protein. Further-
more, since the oil is not fully extracted by pressing, the ‘‘cakes”’ are
also an important source of fat. Thusit would seem that the extensive
studies which have already been made of the soy-bean and peanut
proteins are of a very definite value and that further studies of the
possible uses and value of high-grade soy-bean and peanut press cakes
for human food are to be desired.
FACTORS CONSIDERED IN DETERMINING FOOD VALUE OF A PROTEIN.
In considering the value of any material as a source of protein
for food purposes, at least three factors are ordinarily considered,
namely, the amount, the quality, and the digestibility of the protein
supplied by the material in question. The amount of the protein
present in the material under consideration is determined by chemical
analysis. The quality of the protein ordinarily is determined by
either, or preferably both, of two methods: By ascertaining the num-
ber and nature of the amino acids making up the protein molecule,
1 Personal communication, Forage Crop Investigations, Bureau’Plant Industry.
2 Personal communication, Bureau of Chemistry.
DIGESTIBILITY OF SOY-BEAN AND PEANUT FLOURS. 5
or by ascertaining the biologic value of the protein by means of care-
fully controlled feeding experiments with laboratory animals. Such
experiments give data regarding the ability of a protein to support
normal life processes, such as growth, maintenance, and reproduction.
The amount of protein retained for body uses from the food eaten is
generally determined by digestion experiments in which the protein
under consideration appears as the sole or major portion of the protein
in the diet.
The amount of protein supplied by soy-bean and peanut press-cake
flours would obviously vary somewhat with the varieties of the
legumes from which the flours were made and with the process of
manufacture. Proximate analysis of the dried soy beans and pea-
nuts shows them to have the following composition: Soy beans,!
water 9.9 per cent, protein 36.5 per cent, fat 17.5 per cent, carbo-
hydrates 30.8 per cent, and ash 5.3 per cent, the fuel value being
approximately 1,950 calories per pound; peanuts’, water 9.2 per
cent, protein 25.8 per cent, fat 38.6 per cent, carbohydrates 24.4
per cent, and ash 2 per cent, the fuel value being approximately
2,480 calories per pound. When the oil is expressed from these
legumes the percentage of protein is correspondingly increased and
the resulting commercial press cakes ordinarily contain from 40
to 50 per cent of protein. The press cakes used in the study here
reported, which were obtained by expressing oil from soy beans
and peanuts in a small-sized expeller type of oil press, contained a
larger amount of protein. But in any case the press cake should be
classed as protein-rich material and on the basis of chemical analysis
alone may well be considered as valuable food material. In order to
ascertain the true value of these proteins for dietary purposes it
is necessary to consider the factors referred to above, first, the
- quality of the protein as shown by the nature of the amino acids sup-
plied and by its biologic value, and second, the digestibility of the
protein. —
THE AMINO ACIDS SUPPLIED BY SOY-BEAN AND PEANUT PROTEINS AS
COMPARED WITH THOSE SUPPLIED BY COMMON CEREAL PROTEINS.
Since in the commercial utilization of soy-bean and peanut flours as
human food these flours would, in all probability, be grouped with
the cereal flours and meals, it is natural to compare the amino acids
obtained from glycinin, the principal protein of soy beans, and
arachin, the principal protein of peanuts, with gliadin, zein, rye-pro-
lamin, oryzinin, and hordein, the principal proteins of wheat, corn,
rye, rice, and barley, respectively.
Plant Industry.
2U.S. Dept. Agr., Office Expt. Stas. Bul. 28 (1899), pp. 75.
6 BULLETIN 717, U. S. DEPARTMENT OF AGRICULTURE.
A review of the literature of protein chemistry shows that while in
general they are of a very complex structure the vegetable proteins
yield on hydrolysis nearly all of the 16 amino acids which normally
result from the decomposition of protein material. While all of these
amino acids supply elements of value for food purposes, the results
of carefully-controlled feeding experiments show conclusively that
the dietary value of the different amino acids varies materially.
No résumé of the literature of protein and amino acid chemistry
would be complete without special reference to the extensive investi-
gations of Osborne’ to whom the present interest in this subject is
in no small measure due. In this brief discussion of amino acids it is
impossible to more than refer to the investigations which have been
carried out by Osborne. et al.,27 Henderson and Dean,? Kauffmann,‘
Cohnheim,® Abderhalden and coworkers,’ Henriques,’ Willcock and
Hopkins,? Miller, Rona and Miiller,’? Michaud," McCollum et al.,”
Folin and Denis, Hart and assistants,’ Kajiura,’* Wheeler,
Underhill,” Nollau and Kastle,'* Johns,'® and Geiling,” to determine
1 Amer. Chem. Jour., 13 (1891), pp. 327-347, 385-414; 14 (1892), pp. 212-224, 629-661, 662-689. Amor.
Chem. Jour., 19 (1897), pp. 236,237. Jour. Amer. Chem. Soc., 16 (1894), pp. 633-643, 703-712, 757-764; 17
(1895), pp. 429-448, 539-567, 587-603. 19 (1897), pp. 525-532. Ztschr. Physiol. Chem.,33 (1901), pp. 225-239,
240-292. Amer. Jour. Physiol., 5 (1901), pp. 180, 181. Jour. Amer. Chem. Soc., 24 (1902), pp. 140-167.
Proc. Soc. Expt. Biol. and Med., 5 (1908), pp. 105-107. Science, n. ser., 28 (1908), pp. 417-427. The Vege-
table Proteins [London], Longmans, Greenand Co.,1909. Ergeb. Physiol., 10 (1910), pp. 47-215.
2 Jour. Amer. Chem. Soc., 16 (1894), pp. 778-785; 18 (1896), pp. 536-542, 542-558, 575-582, 583-609, 609-623;
19 (1897), pp. 454-482, 482-487, 487-494, 494-500, 509-513; 20 (1898), pp. 348-362, 362-375, 393-405, 406-410,
410-419, 419-428; 22 (1900), pp. 379-413; 25 (1903), pp. 323-353, 474-478, 837-842, 842-848, 848-853, 853-855.
Amer. Jour. Physiol., 13 (1905), pp. 35-44, 436-447; 14 (1905), pp. 151-171, 259-286; 15 (1906), pp. 333-356;
17 (1906), pp. 231-265; 18 (1907), pp. 123-128, 295-308; 19 (1907), pp. 53-60, 117-124, 468-474, 475-481; 20 (1908),
pp. 470-476, 477-493, 494-499; 22 (1908), pp. 362-372, 423-432; 23 (1908), pp. 180-200. Jour. Biol. Chem., 3
(1907), pp. 213-217, 219-225; 5 (1908), pp. 187-195, 197-205. Amer. Chem. Jour., 15 (1893), pp. 392-471.
Jour Biol. Chem., 10 (1911), No. 10, pp. 303-325; 12 (1912), No. 3, pp. 473-510, figs. 26; 13 (1912), No. 2, pp.
233-276, figs. 21; 14 (1913), No. 5, pp. 481-487; 17 (1914), No. 3, pp. 325-349, figs. 8; 18 (1914), No. 1, pp. 1-16,
figs. 6; 20 (1915), No.3, pp.-351-378, fig. 10; 22 (1915), No. 2, pp. 241-258, fig. 1; pp. 259-280; 25 (1916), No.1,
pp. 1-12, figs. 4; 29 (1917), No. 1, pp. 69-92, fig. 1.
3 Amer. Jour. Physiol., 9 (1903), No. 6, pp. 386-390.
4 Arch. Physiol. [Pfliiger], 109 (1905), No. 9-10, pp. 440-465.
5 Hoppe-Seyler’s Ztschr. Physiol. Chem., 49 (1906), No. 1, pp. 64-71.
6 Hoppe-Seyler’s Ztschr. Physiol. Chem., 47 (1906), No. 4-6, pp. 354-358; 51 (1907), p. 232; 77 (1912), No.1,
pp. 22-58; 81 (1912), No. 4, pp. 323-328. Synthese der Zellbaustine in Pflanze und Tier. (Berlin, Julius
Springer], 1912, p. 128.
7 Hoppe-Seyler’s Ztschr. Physiol. Chem., 49 (1906), No. 2-3, pp. 113-123; 60 (1909), No. 2, pp. 105-118.
8 Jour. Physiol., 35 (1906), No. 1-2, pp. 88-102.
9 Arch. Physiol. [Pfluger], 112 (1906), No. 5-6; pp. 245-291, pls. 2, fig. 1.
10 Hoppe-Seyler’s Ztschr. Physiol. Chem., 50 (1907), No. 4-5, pp. 263-280.
u Ztschr. Physiol. Chem., 59 (1909), No. 5-6, pp. 405-491.
12 Amer. Jour Physiol., 29 (1911), No. 2, pp. 215-237. Jour. Biol. Chem., 19 (1914), No. 3, pp. 323-333; 2.
(1915), No. 1, pp. 181-230, figs. 42; 20 (1915), No. 3, pp. 415-428, figs. 12; 28 (1916), No.1, pp. 153-165, figs. 10,
No. 1, pp. 211-229, figs. 17; No. 2, pp. 483-500, pl. 1, figs. 12.
13 Jour. Biol. Chem., 11 (1912), No. 1, pp. 87-95.
14 Jour. Biol. Chem., 13 (1912), No. 2, pp. 133-153, figs. 4; 19 (1914), No. 3, pp. 373-395, pl. 1, figs.11. Wis-
consin Sta. Research Bul. 17 (1911), pp. 205, pls. 19. Jour. Biol. Chem., 25 (1916), No. 2, pp. 239-260, pls. 9,
figs. 9; 29 (1917), No. 1, pp. 57-68, pl. 1.
15 Bio-Chem. Jour., 6 (1912), pp. 171-181.
16 Jour. Expt. Zool., 15 (1913), pp. 209-223.
17 The Physiology of the Amino Acids, F. P. Underhill, New Haven: Yale Univ. Press, 1915, pp. 169, pl.
1, figs. 13.
18 Amer. Jour. Physiol., 39 (1915-16), No. 2, pp. 162-171, pls. 8. Kentucky Sta. Bul. 197 (1916), pp. 21,
pls. 16.
19 Jour. Biol. Chem., 28 (1916), No. 1, pp. 59-65, 67-75, 77-87.
20 Jour. Biol. Chem., 31 (1917), No. 1, pp. 173-199.
DIGESTIBILITY OF SOY-BEAN AND PEANUT FLOURS. "q
the nature and nutritive value of proteins, especial attention being
given to the amino acids supplied. While it was found that under
some conditions tyrosine, cystine, arginine, histidine, glutamic and
aspartic acids may act as limiting factors in the diet, it seems to be
very generally recognized by these students of nutrition that the two
amino acids, lysine and tryptophane, are of especial importance in
the dietary, lysine being essential for ‘‘growth” and tryptophane
essential for ‘‘maintenance.’’ In view of these conclusions it ap-
pears desirable to compare the amino acids resulting from the hydroly-
sis of soy-bean and peanut proteins with those obtained by the hy-
drolysis of the common cereal proteins. The amounts of amino acids
resulting from the hydrolysis of the principal proteins of some com-
mon cereals are brought together in the following table for comparison
with those obtained by hydrolyzing glycinin and arachin:
Amino acids resulting from hydrolysis of proteins of cereals.
Glycinin a Arachin,9
ig : | Gliadin,| Zein,3 Rye,! Or yzinin,| Hordein,’
Amino acids. wheat.| corn. |prolamin.| rice. barley. |soybean.| peanut.
Glycine cs RiAANS RL REI O rR 8 9 Pe eos 10.00 0. 00 0.13 5(?) 0. 00 0. 97 0.00
PAULI ITI GA sss ae eee pee 12.00 9.79 1.33 53.7 43 hee ae 4.11
ate
Waline?: soe oa a a me eS 1 3.34 1.88 | Not iso- 5(?) 13 .68 1.13
lated
WAIECING Meets ee ee 16.62 19. 55 6. 30 514.3 5. 67 8.45 3.88
IPTOMNO Rete rae oe one n eee oe 113.22 9. 04 9. 82 53:3 IBY Ti 3h Ui 1.37
Phenylalanme..... .... - 22 =-3-.- 1 2. 35- 6. 55 2:40 1-5 2:0 5. 03 3. 86 2.60
Aspartic acid ..... tas See 1,58 Lec 25 o 4 ne ee 3. 89 5.25
ated.
Glutamic activo ess ae en 1 43. 66 26.17 38. 05 514.5 43. 20 19. 46 16. 69
Serine See one a ee ee 1.13 O25 06 (®) Not iso- | Not iso- | Not iso-
; lated lated lated.
IS WROSINIGS srs =f o=e aa ae S 11,20 3.55 1.19 5.5 i 1. 67 1.86 5.50
@yshineys3s225 eer ee ee Lordy ype Beye cie: tl Not esti- 61.26 | Not esti-|-2 22.22.22 1.85
mated. mated. }
IAT SININGS sat aso ess 22s = | 13.16 155 2.22 69.15 2.16 5. 12 13.51
ERISHI GING: Seen aes ae et | 22.19 . 82 .39 6 3.32 1. 28 1.39 1.88
mcinereetee eis Ek Ae pve dot 00 .00| 64.26 00 2.71 4.98
IMI ON eC eee saan See ee 15,22 3. 64 5.11 6 3.23 4.87 2.56 2.03
Tryptophane .....-..-.-----.---| 11.00 .00 | Present. ) Present. | Present. | Present.
1 Jour. Biol. Chem., 9 (1911), No. 5, p. 426.
2 Jour. Biol. Chem., 22 (1915), No. 2, p. 261.
3 Amer. Jour. Sen ysiol, 26 (1910), No. 4, p. 304.
4 Osborne, Ergeb. Physiol., 10 (1910), p. 86. (In the absence of a name for rye protein, Osborne Paterked
to the alcohol soluble protein as rye prolamin.)
5 Osborne, Ergeb. Physiol., 10 (1910), p. 112.
6 Jour. Biol. Chem., 22 (1915), No. 2, p. 275.
7 Osborne, Ergeb. Physiol., 10 (1910), p. 90
8 Osborne, Ergeb. Physiol., 10 (1910), p. 132.
9C.O. Johns and D. B. Jones. To be published in the Journal of OEE Chernigtey.
It will be noted on referring to the above table that the earlier
analyses of gliadin, zein, rye-prolamin, oryzinin, and hordein indi-
cated that these proteins supplied little if any lysine and tryptophane.
In the more recent studies of oryzinin and gliadin it was found that
on hydrolysis these proteins yield appreciable amounts of lysine. An
unpublished investigation by C. O. Johns and A. J. Finks, Bureau of
Chemistry, shows that hordein on hydrolysis yields approximately the
8 BULLETIN 717, U. S. DEPARTMENT OF AGRICULTURE.
same amountof lysine as gliadin. However, the amount of these cereal
proteins in some of the cereals is insufficient to supply adequate
amounts of the essential amino acids, whereas soy beans and peanuts
are rich in glycinin and arachin which yield a high percentage of
lysine. In considering the dietary value of glycinin and arachin,
from the standpoint of lysine and tryptophane, the consensus of
opinion of biochemists seems to be well summed up in the conclusions
of Osborne and Mendel? who state ‘‘ We have shown that growth does
not occur when lysine is lacking from the diet but takes place
promptly on adding this amino acid to the otherwise adequate food,”
and in the conclusions expressed by Abderhalden,? who says that
tryptophane is an indispensable component in the dietary.
It may also be noted, in discussing the relative nutritive value of
proteins as regards the presence or absence of lysine and tryptophane,
that Osborne and Mendel? state that lysine must be present in the
diet since ‘‘the animal organism apparently can not synthesize
lysine.’”’ These authors ‘ also state that ‘‘Tryptophane can not be
synthesized by the animal cells.” Accordingly, a theoretical con-
sideration of the relative nutritive value of soy-bean and peanut pro-
teins, based upon their amino-acid content alone would indicate that
glycinin and arachin possessed a greater dietary value than the prin-
cipal proteins supplied by the common cereals.
BIOLOGIC VALUE OF SOY-BEAN AND PEANUT PROTEINS AS COMPARED
WITH THAT OF COMMON CEREAL PROTEINS.
Feeding experiments have been made by a number of investigators
for the purpose of securing data regarding the relative biological
value of proteins supplied by some of the cereals referred to above.
Willcock and Hopkins ® state that ‘‘loss of weight begins the moment
it [zein] forms the sole nitrogenous supply.”” Osborne and Mendel ®
report ‘‘We have now accumulated the results of a large experience
in feeding zein, with the uniform consequence of decline when this
protein forms the sole nitrogenous component of the dietary.” These
results have been confirmed by Wheeler’ in studies with rats and
later by Hart and McCollum,’ who report that young pigs can not
grow when the maize kernel is the sole source of nutriment. Hogan °
conducted experiments to determine the value of corn protein, zein,
when fed as the sole source of protein, and concluded that trypto-
1 Jour. Biol. Chem., 25 (1916), No. 1, p. 2, figs. 4.
2 Hoppe-Seyler’s Ztschr. Physiol. Chem., 96 (1915), No. 1-2, pp. 1-147.
3 Jour. Biol. Chem., 17 (1914), No. 3, p. 334.
‘Ibid., p. 328.
5 Jour. Physiol., 36 (1906), No. 1-2, p. 100.
6 Jour. Biol. Chem., 17 (1914), No. 3, p. 338.
7 Jour. Expt. Zool., 15 (1913), No. 2, pp. 209-223.
8 Jour. Biol. Chem., 19 (1914), No. 3, pp. 373-395, pls. 2, figs. 11.
9 Jour. Biol, Chem., 29 (1917), No. 3, pp. 485-493, figs. 3.
DIGESTIBILITY OF SOY-BEAN AND PEANUT FLOURS. 9
phane was the first limiting factor and lysine the second when all
other factors known to be essential to the dietary have been supplied.
The nutritive value of the principal protein of wheat, gliadin, has
also been carefully studied. Osborne and Mendel! found that ‘‘in
order to promote the growth of experimental animals it is necessary
to supplement gliadin with lysine.”
Hart and McCollum? report ‘‘It is evident that the whole-wheat
grain will not sustain growth and even leads to physiological disturb-
ances when continued as the sole source of nutrients for but a short
span of the entire period of growth.’”’ In a later paper Hart, McCol-
lum, Steenbock, and Humphrey * conclude that an exclusive diet of
wheat grain and wheat straw is wholly inadequate with heifers for
reproduction and in some instances for continued growth.
The proteins of rye, rice, and barley have received much less atten-
tion by investgators than those of wheat and corn. It appears that
while rice and barley supply small amounts of total protein, orzinin
and hordein supply relatively large amounts of lysine. Osborne,
Van Slyke, Leavenworth, and Vinograd‘ in comparing the basic sub-
stances yielded by the proteins of the endosperm of wheat (lysine 1.58),
maize (lysine 0.97), and rice (ysine 4.26) with the figures reported by
Thomas * for the percentage of assimilable nitrogen 40 per cent, 29
per cent, and 88 per cent, respectively, say “It is rather striking that
the figures for the utilizability of these proteins correspond so closely
with the lysine which they yield.”
Buckner, Nollau, and Kastle* in experiments with chickens in-
cluded a diet in which both barley and rice were fed in conjunction
with hominy, oats, and gluten, and were of the opinion that the
unsatisfactory growth which resulted could be attributed to the low
lysine content of the diet, which probably means that only small
quantities of rice were eaten. Osborne and Mendel report feeding
experiments with rats in which concentrated oat, rice, and barley
proteins were added to an otherwise adequate diet. They state’ that
“the total proteins of rice and barley in contrast with maize and oats,
when furnished in diets containing 16 to 17 per cent of protein,
supply enough of all the amino acids essential for growth.”
It is interesting to compare these conclusions regarding the value
of the cereal proteins with the conclusions reported regarding the
value of soy-bean and peanut proteins. In a study of the relative
value of some common proteins as supplements to corn gluten Os-
1 Jour. Biol. Chem., 17 (1914), No. 3, pp. 325-349, figs. 8.
2 Jour. Biol. Chem., 19 (1914), No. 3, p. 276.
8 Loe. cit.
4 Jour. Biol. Chem., 22 (1915), No. 2, p. 276.
5 Arch. Anat. u. Physiol., Physiol. Abt., 1909, pp. 257, 259, 261,
6 Amer. Jour. Physiol., 39 (1916), No. 2, pp. 162-171.
7 Jour. Biol. Chem., 34 (1918), No. 3, p. 531,
64347°—18—Bull. 7172
10 BULLETIN .717, U. S. DEPARTMENT OF AGRICULTURE.
borne and Mendel’ included experiments with a commercial soy-
bean flour and a peanut meal (prepared by. grinding peanuts from
which the oil had been extracted) in a series containing such mate-
rials as casein, lactalbumin, edestin, cottonseed protein, fish-meat
meal, corn-oil cake, ‘‘vegetable-albumin flour” (largely gliadin),
brewers’ grains (largely residues of corn and barley proteins), and
pea meal. The authors state, ‘‘An inspection of these tables shows
that lactalbumin is the most efficient a which are
equally efficient are milk albumin and soy-bean flour.” The gain in
weight reported for the experimental animals which were fed a diet
ltiels included the peanut meal indicated that this material ranks
high as a supplement to corn gluten. Asa result of these facts the
authors conclude that ‘The efficiency of these supplements presum-
ably depends essentially upon their relative content of lysine and
tryptophane.”
Osborne and Mendel report ? in a study of the relative values for
functions of erowth of isolated proteins included in a diet consisting
of an isolated protein, protein-free milk, starch, agar, and fat that
they were able to secure active growth with casein, ovalbumin,
lactalbumin, edestin, glutenin, and glycinin (soy-bean protein), and
that they uote little or no growth with gliadin, hordein, and zein.
Osborne and Mendel * in a report of results of experiments made
with rats say ‘‘On diets containing either the soy-bean meal or the
commercial soy-cake meal, together with fats and ‘ Protein-free
milk” or our ‘‘artificial’’ salt mixture, several broods of vigorous
young have been produced, and these young have grown normally on
diets the same as those on which their parents were raised. This isa
further demonstration of the nutritive efficiency of this legume, in
striking contrast vo the adverse results obtained with kidney beans
and garden peas.”’
Daniels and Nichols * as the result of experiments with rats con-
ducted to determine the biologic value of protein supplied by soy
beans which had been cooked 30-40 minutes under 15 pounds pres-
sure concluded that—
The value of the protein of the soy bean has been demonstrated in all of our experi-
ments. That animals fed rations containing 15.6 and 18.7 per cent of protein obtained
solely from the soy bean have grown normally and in the latter case * * * [with
the larger percentage of soy-bean protein] have produced successive litters ef young,
which in turn have reproduced, is sufficient evidence that the protein of the soy bean
fulfills all physiologic requirements. The protein of the soy bean appears to. be quite
as valuable as the casein of milk. These findings are somewhat surprising in view of
the fact that the protein of other legumens, namely peas and white beans, has been
found wanting.
1 Jour. Biol. Chem., 29 (1917), No. 1, p. 77.
2 Carnegie Inst. Washington Pub, No. 156, pt. 2, p. 83.
3 Jour. Biol. Chem., 32 (1917), No. 3, p. 375.
4 Jour. Biol, Chem., 32 (1917), No. 1, p. 95.
DIGESTIBILITY OF SOY-BEAN AND PEANUT FLOURS. 11
While several investigators are giving attention to the nature and
value of the peanut proteins, as yet little information has been
reported regarding the biologic value of these proteins. Daniels and
Loughlin 1 have recently reported a study of two peanut meals; one
of which was ground roasted peanuts which contained the normal
amount of peanut oil, the second was ground press cake which con-
tained a relatively small amount of peanut oil. Regarding the bio-
logic value of peanut proteins the authors state—
Rations consisting of 67.5 grams of peanut meal, supplying 18 per cent protein, 10
crams of lard, 5 grams of butter fat, 11.4 grams of cornstarch, and 5.09 grams of suitable
inorganic material proved satisfactory in every way. The curves of growth * * *
[as one of the charts accompanying the paper shows] in all cases were similar to those
generally considered to be normal. Reproduction occurred at frequent intervals and
three generations were obtained. Good growth was secured also with a ration supply-
ing 15 per cent protein from the peanut meal. The proteins of peanuts are comparable
to those of the soy bean, since it has been shown that both legumes supply the essen-
tial amino acids in sufficient amounts for normal growth and reproduction.
In discussing the value of soy-bean flour it should also be noted that
this material is especially valuable for food purposes since it supplies
the water-soluble and to a limited extent the fat-soluble accessories
essential in a complete diet. In this connection Daniels and Nichols ?
say:
It contains a high percentage of a physiologically good protein, a considerable
amount of energy-yielding material in the form of fat and carbohydrate, and a fairly
liberal supply of the fat-soluble food accessory, as well as of the water-soluble growth
determinant.
And Osborne and Mendel 3 state that—
So far as we are aware the soy bean is the only seed hitherto investigated, with the
possible exception of flax and millet, which contains both the water-soluble and [in
limited quantity] the fat-soluble unidentified dietary essentials or vitamins. This
fact, taken with the high physiological value of the protein, lends a unique signifi-
cance to the use of the soy bean as food.
Referring to the presence of the fat-soluble and water-soluble food
accessories in peanut meal Daniels and Loughlin * say:
That peanuts are lacking in the fat-soluble food accessory has been shown by the
behavior of animals which were given rations containing no butter fat * * *
Since all the animals receiving the 5 per cent butter-fat ration were normal in every
respect, proof is furnished for the presence of a considerable amount of the water-
soluble food accessory in the diets. When the peanuts formed 56 per cent of the ration,
there was sufficient water-soluble B for the experimental animals. Like the soy bean,
it needs only to have added suitable inorganic material zine some of the fat-soluble
food accessory to make it a complete food.
1 Jour. Biol. Chem., 32 (1918), No. 2, p. 296.
2 Jour. Biol. Chem., 32 (1917), No. 1, p. 96.
3 Jour. Biol. Chem., 32 (1917), No. 3, p. 376.
4 Loc. cit.
12 BULLETIN 717, U. S. DEPARTMENT OF AGRICULTURE.
Osborne and Mendel‘ also report that they have been able to
demonstrate the presence of the water-soluble food accessory in
peanut meal.
In summarizing the studies of the nature and value of soy-bean
and peanut proteins, referred to above, it appears first that chemical
analysis of glycinin and arachin shows them to be relatively rich in
lysine and tryptophane, amino acids essential for growth and main-
tenance, and second that studies of their biologic value show them to
be more efficient proteins than those supplied by the common cereals
or many of the common legumes. It appears then from these facts
that soy-bean and peanut proteins have a high nutritive value and
that further studies of their value in the human dietary are to be
desired.
THE DIGESTIBILITY OF SOY-BEAN AND PEANUT PROTEINS.
This investigation was undertaken for the purpose of determining
the digestibility of these proteins by normal individuals when eaten
as a constituent of a simple mixed diet. It is of course recognized
that the oil remaining in the soy-bean and peanut flours contributes
to the food value of these flours, but no special attention is given to
these oils in this study since previous studies of peanut ? and soy-bean
oils ? have shown that both are very well utilized by the human body.
PREPARATION OF SOY-BEAN AND PEANUT PRESS-CAKE FLOURS. *
The soy-bean flour used in the experiments which follow was pre-
pared by expelling the oil from 2 bushels of well-cleaned Mammoth
Yellow soy beans which had been grown under controlled experi-
mental conditions by Forage Crop Investigations of the Bureau of
Plant Industry. In order to secure a more nearly complete removal
of the oil than is usual, the cake was pressed a second time. The
press cake thus obtained was of a yellow color and retained about 8
per cent of oil. It was ground in a small-sized burr mill until all of
the meal passed through a millimeter sieve. Through the courtesy
of H. 8. Bailey, of the Bureau of Chemistry, it was possible to pre-
pare both the soy-bean and peanut flours under conditions approxi-
mating those of the commercial oil mill, using for this purpose a
continuous process expeller type of oil-expressing machine.
In order to secure data relative to the fineness of this flour, a sam-
ple was bolted, and it was found that 53 per cent of the flour re-
mained on the 40-mesh sieve, 23 per cent remained on the 70-mesh
sieve, 9 per cent remained on the 90-mesh sieve, 3 per cent remained
1 Jour. Biol. Chem., 32 (1917), No. 3, p. 310.
2U.S. Dept. Agr. Bul. 505 (1917), p. 18.
3U.S. Dept. Agr. Bul., 687 (1918), p. 6.
4In this paper the term ‘‘flour’”’ is used without reference to the coarseness of the ground soy-bean
and peanut press cakes.
DIGESTIBILITY OF SOY-BEAN AND PEANUT FLOURS. 13
on the 109-mesh sieve, and 12 per cent passed through the 109-mesh
sieve. In view of the high protein content of the soy-bean press
cake it seemed of interest to determine whether the distribution of
nitrogen was uniform for the fractions remaining on the different-
sized sieves. For this purpose a press cake which had been ground to
duplicate the fineness of commercial soy-bean flour was chosen. That
portion remaining on the 40-mesh sieve contained 5.95 per cent of
nitrogen, that on the 70-mesh sieve 7.62 per cent, that on the
90-mesh sieve 8.06 per cent, that on the 109-mesh sieve 8.21 per
cent, and the portion that passed through the 109-mesh sieve con-
tained 8.32 per cent of nitrogen.
As often prepared in the commercial expression of peanut oil,
the peanut press cake contains, in: addition to peanut kernels, the
shells and the thin red skin which surrounds the kernel. Conse-
quently such commercial press cake, though suited for use as stock
feed or fertilizer, is not suitable for food purposes; especially is this
true when moldy or unsound peanuts are included, when the shells
are dirty, or when the oil is not expressed under sanitary conditions.
In the commercial preparation of ‘‘salted peanuts” clean shelled
peanuts of good quality are ‘‘blanched”’ by subjecting them to an
atmosphere of live steam just long enough to loosen the skin sur-
rounding the kernels but not long enough to allow the kernels to
- absorb any appreciable amount of water vapor. A subsequent agi-
tation of these kernels in a container provided with either a suction
or a blower separates the skins from the kernels. The expression of
oil by the cold process from such kernels produces a virgin oil and a
high-grade press cake rich in protein. If shelled peanuts, from which
the surrounding skin has not been removed, are pressed the resulting
flour, though satisfactory for food purposes, is of a reddish tinge and
has a somewhat different and less-pleasing flavor than that of the
flour prepared from blanched kernels.
In the study here reported of the digestibility of the proteins sup-
plied by peanut flour a series of experiments was made with each of
these types of flours. The peanut flour used in the first series of
experiments was prepared by expressing the oil from blanched,
roasted peanuts and grinding the resulting press cake. The flour
used in the second series of experiments was prepared by the cold
expression of shelled raw peanuts from which the red skin had not
been removed. ‘The reddish flour obtained did not possess the rich
nut-like odor of that obtained from roasted kernels. A sample of
the flour from the unroasted peanuts was bolted and sieved to secure
data regarding its fineness, and it was found that 54 per cent of the
flour remained on the 40-mesh sieve, 23 per cent on the 70-mesh
sieve, 13 per cent on the 90-mesh sieve, 5 per cent on the 109-mesh
sieve, and 5 per cent passed through the latter sieve.
14 BULLETIN 717, U. S. DEPARTMENT OF AGRICULTURE.
THE SUBJECTS OF THE DIGESTION EXPERIMENTS.
Seven subjects with previous experience in experiments which
were made to determine the digestibility of some edible fats assisted
in this investigation. In general they were students of dental or
medical schools and were of normal health and appetite. Their.
ages ranged from 20 to 40 years and their activities were such that
they would be classified as moderately-active persons. As is always
the case, they were instructed to exercise care in saving all uneaten
portions of the food, in separating and collecting the feces, and in
submitting reports concerning their physical condition before, after,
and during the experimental period. Inasmuch as all seemed in
their usual good physical condition throughout the entire time of
the experiments, no detailed discussion of these reports is given.
- PREPARATION OF EXPERIMENTAL DIETS.
As in all studies of this character, it was desired that the nutrient —
under consideration, in this case the proteins supplied by soy-bean
and peanut flours, should comprise as large a portion as possible of
the total protein of the diet. It is essential that the foods studied
be prepared in an acceptable form and accordingly preliminary tests
were made of a number of methods of preparing these flours for
eating. As a result of these tests it appeared that ‘‘tea biscuits”’
similar to those so commonly made with wheat flour were well adapted
to this purpose. The recipe used follows: y
RECIPE FOR BISCUITS. -
16 cups flour mixture. 12 teaspoons salt.
16 tablespoons lard. 10 tablespoons baking powder.
6 cups water.
In the soy-bean experiments the flour mixture was prepared by
mixing equal portions of wheat flour and soy-bean flour. In the
experiments with the peanut flour made from roasted kernels, the
proportion was two-thirds wheat flour and one-third peanut flour,
and in the experiments with peanut flour made from the raw kernels
from which the red skin was not removed, the proportion was one to
one. The wheat flour used in all cases was a commercial brand of
patent flour.
Biscuits made with flour and soy-bean flour or peanut flour one to
one were satisfactory when only one-half or three-fourths inch in
thickness; thicker biscuits being very often rather ‘‘heavy,” no doubt
because the amount of gluten in the flour mixture was rather small.
It was found that if the biscuits were very thoroughly baked (though
not scorched) they possessed a much better flavor than those not so
well done.
DIGESTIBILITY OF SOY-BEAN AND PEANUT FLOURS. re
In order that the major portion of the protein supplied by the
experimental diet should be derived from the soy-bean and peanut
flours, the accessory foods were chosen to supply only a minimum of
protein, and included oranges, butter, and tea or coffee with sugar if
desired. Since the subjects ate very generous amounts of the bis-
cuits but had a very limited diet in other respects it was thought that
they would use large quantities of butter. It was found, however,
that though they could have all they wanted they ate on an average
only about 56 grams daily.
DETAILS OF THE EXPERIMENTS.
In this study of the digestibility of the proteins supplied by soy-
bean and peanut flours the methods which were employed were very
similar to those followed in the study of the grain sorghums.!| The
usual 3-day or 9-meal experimental period was considered satis-
factory for this study. No attempt was made to maintain a uniform
body weight of the subjects or to maintain nitrogen equilibrium
during the period. As is usual in such cases, sufficient food material
was prepared at one time to supply all the subjects for the entire
experimental period, representative samples of all the foods being
retained for analysis. These samples and those of the air-dried
feces of each subject resulting from the experimental diet were ana-
lyzed in the usual way. The differences between the amounts of pro-
tein, fat, and carbohydrates present in the foods and in the feces were
taken to represent the amounts of these constituents digested. This
method of procedure gives data regarding the digestibility of protein,
fat; and carbohydrate supplied by the entire diet. Since in this
study the coefficients of digestibility of the soy-bean and peanut pro-
teins are of special interest they have been estimated by making
allowance for the undigested protein material occurring in the fen
~The method followed in estimating the digestibility of the proteins
_supplied by the soy beans and peanuts is indicated by the following
~ equations:
[Weight of protein in accessory food are x [Percentage of
undigested protein in each]=[Protein in feces from food other than
- bread]. :
_ [Total protein in feces]—[Protein in feces from food other than
bread]=[Weight of undigested bread protein. |
[Weight of protein in bread]—[Weight of undigested bread pro-
tein]+[Weight of protein in bread] =[Estimated percentage of avail-
ability of bread protein.]
In determining the amount of undigested protein present in the
accessory food materials in the experimental diet it was assumed that
1U.S. Dept. Agr. Bul. 470 (1916), pp. 30.
16 BULLETIN 717, U. S. DEPARTMENT OF AGRICULTURE.
the protein! of wheat flour was 93.8 per cent digested, the protein? of
orange 85 per cent, and the protein? of butter was 97 per cent
digested. |
It is, of course, recognized that the calculated values so obtained,
for a special food, in this case soy-bean and peanut proteins, are
probably somewhat low, since they include the errors due to consider-
ing all fecal nitrogen not resulting from the accessory foods as undi-
gested soy-bean or peanut nitrogen, whereas fecal nitrogen, as has
been pointed out by Woods and Merrill,? Crowther and Woodman,*
and others, is derived in part at least from bile residues, epithelial
waste, stomach residues, mucus, and saliva. It is not believed,
however, that in this instance the error occasioned by the inability to
correct for this factor is significant, especially in view of the unusually
large quantities of soy-bean or peanut proteins consumed.
THE DIGESTIBILITY OF PROTEIN SUPPLIED BY SOY-BEAN PRESS-
CAKE FLOUR.
In spite of the very extensive use of soy beans by the oriental
peoples there appears to be little experimental data reported regard-
ing the digestibility of the proteins supplied by this protein-rich
legume. However, the long use of the soy bean as a staple article
of the diet by the Japanese and Chinese offers sufficient evidence that
soy-bean protein is well tolerated by the human body. Oshima in a
summary of Japanese nutrition investigations, which includes much
interesting information regarding the digestibility of preparations of
legumes in common use in Japan, reports three experiments * in which
the subjects ate approximately 200 grams of tofu (soy-bean curd)
daily in conjunction with cooked rice, The average digestibility of
the total protein supplied by these diets, of which 83 per cent was
soy-bean protein, was 95 per cent, | |
Few studies of the digestibility of soy-bean protein have been made
in this country, Mendel and Fine report ® an experiment of six days’
duration in which soy beans supplied 90.5 per cent of the total
nitrogen intake, the basal ration consisting of tomatoes, apples,
oranges, milk, sugar, and butter. Thesoy beans were boiled in water
for one-half hour and the tomatoes thoroughly incorporated with the
resulting mush which had been salted to taste. The total nitrogen
supplied by the diet was 85.3 per cent digested. The subject re-
ported that he was in excellent condition throughout the whole
experiment. Defecation was regular and no physiological disturb-
ances were experienced. The same authors conducted two series of
1U.S. Dept. Agr., Office Expt. Stas. Bul. 143 (1904), p. 32.
2 Connecticut Storr’s Sta. Rpt. 1899, p. 104.
3U.S. Dept. Agr., Office Expt. Stas. Bul. 143 (1904), p. 57.
4 Jour. Agr. Sci., 8 (1917), pp. 429-477, Part IV.
6U.S. Dept. Agr., Office Expt. Stas. Bul. 159 (1905), pp. 224.
6 Jour. Biol. Chem., 10 (1911), pp. 433=458.
DIGESTIBILITY OF SOY-BEAN AND PEANUT FLOURS. Li.
digestion experiments with laboratory animals (dogs). In the first
series (three tests) the animals received a mush prepared by heating
soy beans, lard, agar, bone ash, and water on a water bath for 4 to 6
hours. In the second series (nine tests) the animals were ‘‘subjected
to a thorough treatment with indigestible nonnitrogenous materials,
to remove, as far as possible, the accumulated intestinal débris,”’ and
were fed a mixture of soy beans, sugar, and lard which was allowed
to stand in water overnight. During the first series the animals ate
an average of 86 grams of soy beans daily and an average of 58 grams
in the second series. The digestibility of the total nitrogen of the
diet was for the first series 80 per cent and for the second 84 per cent.
In the present study the seven experiments conducted to determine
the digestibility of the protein supplied by soy-bean flour were divided
into two series, one of four and one of three tests. The interval be-
tween first and second series comprised a rest period of two days on
an ordinary mixed diet followed by an experimental period of three
days during which the digestibility of a vegetable fat was studied and
this by a second rest period of four days on an ordinary mixed diet.
The experimental conditions and the subjects were identical for both
series of experiments. Four subjects living under normal conditions
assisted in the experiments which are reported in the following tables:
Data of digestion experiments with soy-bean flour in a simple mixed diet.
Constituents of foods.
Experiments, subjects, and diet. aight | ees
; . arbo-
Water. | Protein. | Fat. hydrates. Ash. .
Experiment No. 669, subject A. F.: Grams. | Grams. | Grams. | Grams. | Grams. | Grams.
Biscuits containing soy-bean flour. 1, 396.0 456. 1 254.8 129.1 497.8 58. 2
POUL eee 1c eS eet 828.0 719.5 6.6 1.7 96.1 4.1
Butter Got ee eee es tice saioed 210.0 23.1 2.1 NB lesasdeaeee 6.3
SYD TPN RSS, MES MEARE SIG yA en 135.10) | oes ee serail epee eee IBIS O |lssoococce
Total food consumed................ 2,569.0 | 1,198.7 263.5 309. 3 728.9 68.6
LOSES IE 5 2s os oP HE ae ry ne ee 84. Obl. See ee 29. 4 16.4 21.6 16.6
PALO MEIN GaUI ULNA Oe pose pores ara by aVereroie ie ace] Srarsicte/ele = 2 sil'sisemjereevale 234 1 292.9 707.3 52.0
Bencentmiiized@eemen sce ce cee ss alee nce nge. lsc ees ee tee 88.8 94.7 97.0 75.8
Experiment No. 670, subject P. K.:
Biscuits containing soy-bean flour..... 1,571.0 513.3 286. 7 145.3 560. 2 65. 5
INR SSeldine Soece. Gaon eee =a anne 410.0 356.3 3.3 : 47.6 2.0
JBUU IANS) CS eee Sc Ook ke ae 316.0 34.8 3.1 P1Neb).|So5acoa00c 9.5
SUPA eae mc tices Saee coatie acle sclec wc cst ASTON ese See tera Nave eta vell cere eh meeets ee WILE O Wososssaces
Total food consumed..............-- 2,478.0 904. 4 293.1 414.7 788. 8 77.0
1DGROSS Tet Soe Coes kor a eee ee 1425 Op Boece 53. 4 33. 4 36.3 18.9
HATTINTET TT OER SV Ze Weis Wares a che Saeed [eS sa Perce ele | 239.7 381.3 752.5 58.1
PRcenieMtilized amen Sect wa. scl aeons [teers eae i esits 91.9 95.4 75.5
Experiment No. 671, subject J.C. M.:
Biscuits containing soy-bean flour . 1,178.0 384. 8 215.0 109.0 420.1 49.1
JAI eek ee ee ee ene eee 446.0 387.6 3.6 “FA9 51.7 4G)
IBS IECLOR ee eemeeesce™ Coe acceso nseceeses < 192.0 21.1 1.9 WIGS = 2! |ecetysracisis 5.8
SS LEAT ees SEO St ate ale inze olan cini dole weiss sie DEG Oulaeerseree sere llecimise eer aalis ctocishiietees BURGH! WEGoocdecos
Total food consumed..............-.- 2, 092.0 793.5 220.5 273.1 747.8 bYfoil
CCES A eres ie aininicie wise cia s adieve etecienic’ O40} |[Ssec cance 36.0 13.4 30. 4 14.2
PR THOMIHAMLUNZOU slate vin oxic ses cole.elsicsis\.5| tenisinaicin alse =e 184.5 259.7 717.4 42.9
POR COMMUN ZORG rm 5 win cc's elas nicecsicie|deca—alsieac|Scinietnwicine 83.7 95.1 95.9 75.1
18
BULLETIN 717, U. S. DEPARTMENT OF AGRICULTURE.
Daia of digestion experiments with soy-bean flour in a simple mixed diet—Continued.
Constituents of foods.
: : es : Weight
Experiments, subjects, and diet. Sieeeis
; : Carbo-
Water. | Protein. Fat. hydrates Ash
Experiment No. 672, subject A. A. R.: Grams Grams Grams Grams. | Grams Grams.
Biscuits containing soy-bean flour..... 1, 296. 0 423.4 236.5 119.9 462. 54.0
TUG a oece eae beeen eee 893.0 776.0 7.1 1.8 103. 6 4,5
Butter 2 Seen ee aeeae ae eee 43.0 4.7 4 SO50 fhe osSuenee 1.3
SUS ais oo ee emcees oe oe eye ee tore b DSO Se Sow sc lece ne eectosl Pee 1545 OMe Js eb. 2S
Total food consumed..............-. 2,386.0 | 1,204.1 244.0 158. 3 719. 8 59.8
BOCES es ae oes See eee oe GO loessscawee 28.5 12.1 25.9 10.5
Amount jtilized to. jose se ores te ae a ese ce 215.5 146. 2 693. 9 49.3
Percentwutilized® £02 be see on, oes s|a eee lode Fe oeere 88. 3 92.4 96.4 82. 4
ASS Ed (er OD ae RAE ee
Experiment No. 678, subject P. K.:
Biscuits containing soy-bean flour..... 1,629.0 528. 0 287.7 83.4 653. 4 76.5
BTUWHG Cece Supe oat eo cmes eee eases 413.0 358.9 3.3 8 47.9 2.1
IBUGCOn: feet eee ote teens sasha 400.0 44.0 4.0 BAO LO MN ocsecs ees 12.0
SUUAT eh. cease ovion emia ste ee = See ee PAG: Oss cece cee cess tiasee See eee 2 ZAG. 0) | sas
Total food consumed............---- 2,688.0| 930.9] 295.0] 424.2| 947.3 90. 6
MIGCES. shee neic sepiene Sema sei tas see emis cae 46,0 Popo a: Zied 13.7 22.3 12.9
AMountdtiilized Boa. bce ae eee eee eee oe ame eae 267.9 410.5 925.0 Ar,
Percent miilized.-. 6o/ 425550. bee eee sees a eee eee 90. 8 96.8 97.6 .8
Experiment No. 679, subject J.C. M.:
Biscuits containing soy-bean flour..... 1, 245.0 403.5 219.9 63.7 499. 4 58.5
COC it een Ree ee Rea pS eee eeoe, 466.0 405.0 3.7 9 54.1 2.3
BULLER Orne face ceuiescs ee ees cae saaces 206. 0 22.6 2.1 2 Gi Is Ae. eee 6.2
SEES 355555 couse so one eS oSsaagobe Saas PAY AUG ease ones Reena 5S ene aes 20460 |Peeee esses
Lotaliood consumed 22. c2-s- esse 2,174.0 831.1 225.7 239. 7 810. 5 67.0
MT ECOSHR re See Meek hee eis I Lee eee S510 Gs Beet 30.3 10.5 30. 4 13.8
AMouNE Utilized 5-02 225. bee Soe c wel sone eee [psa ceaseus 195. 4 229. 2 780. 1 53. 2
Percent utilized: eects. oye oe Rseveean 86.6| 95.6| 96.2| 79.4
Experiment No. 680, subject A. A. R.:
Biscuits containing soy-bean flour..... 1, 239.0 401.6 218. 8 63. 4 497.0 58. 2
[re EY eee getty LS ome ang ie A geen 1,384.0 | 1,202.7 Wee | 2.8 160. 5 6.9
Butter seer ee a see eee eee ae 46.0 5.1 4 BG tad Maem Sta 1.4
SUGST Heat sae see ceca ee eee Cees 250-0 oie wc asismese SSE Toye Me [Epa eeeyete i 230,00 once e eae
Total food consumed..........-.--2- 2,899.0} 1,609.4 230. 3 105.3 887.5 66.5
COCS ESS MR eC Sek ease SL Ul LSet aa re ae 31.6 7.8 40.5 15.1
Amount utilized 528505052. 2k set Spo Ses a 198.7 97.5 847.0 | 51.4
Per cent widized <p 32 05 2 ee ep eM [Tc | 86.3 | 92.6 95.4 | 77.3
Average food consumed per subject per
Cy son ee ee Bi BE is Ee CS 823.1 355. 8 84.4 91.6 | 268.1 | 23.2
Summary of digestion experiments with soy-hean flour in a simple mized diet.
Experiment No. Subject.
GEG E aes os SE oy IAG Hy Se aoe See
GO nee ness eRe oe Peele ee earn
6 Se ee RS rari see FeO.) MIS de
BQ Sa ee a bes PAC AC ERE ee A SE en eee
6182 oe ee ee eee eee PR eet coke otee teee ee
Girne ae LO eR Ee GLORp tee Rare LE eats
GSO 5s Soe se eee LNG NE 8 a a pocke Se
Digestibility of entire ration. Esti-
mated
digesti-
aaa bility of
: ‘ar bo- soy-bean
Protein. Fat. hydrates. Ash protein
alone
Per cent.| Per cent. Per cent. | Per cent.| Per cent.
88.8 94.7 97.0 75.8 88.0
81.8 91.9 95.4 75.5 79.4
83.7 95.1 95.9 qoo8 81.6
88.3 92.4 96. 4 82. 4 87.5
90.8 96.8 97.6 85.8 90.2
86.6 95.6 96.2 79.4 85.2
86.3 92.6 95.4 AR 85.0
86. 94.2 78.8 85.3
DIGESTIBILITY OF SOY-BEAN AND PEANUT FLOUBRS. 19
In the experiments with soy-bean flour the subjects ate on.an |
average 84 grams of protein, 92 grams of fat, and 268 grams of carbo-
hydrate per man per day. The coefficients of digestibility for the
entire diet were, for protemm 86.6 per cent, for fats 94.2 per cent,
and for carbohydrate 96.3 per cent. The digestibility of soy-bean
protein was estimated to be 85.3 per cent. Referring to pages
2 and 3 it will be noted that the digestibility of the proteins of com-
mon legumes, as shown by numerous studies made by well-known
investigators, is noticeably lower than this. It is quite possible that
the method of preparation and of cooking may affect the digesti-
bility to some extent, since in grinding the press cake the cells are
without doubt quite thoroughly broken up. However, in those
studies in which peas were served in the form of a purée the cells were
also very thoroughly broken. The digestibility of soy-bean protein
(85.3 per cent) compares very favorably with that of the common
cereals.
Of the 84 grams of protein eaten daily 82 grams were supplied
by the soy-bean biscuits. Since approximately 85 per cent of the
total protein of the biscuits was soy-bean protein, the subjects ate
on an average 70 grams of soy-bean protein daily. Inasmuch as none
of the subjects reported any physiological disturbances as a result of
this diet, it appears that soy-bean protein is well tolerated by the
human body.
The results of the experiments in general indicate that protein
supplied by soy-bean press cake (ground to flour) is well assimilated
and is too valuable to be overlooked as a human food.
THE DIGESTIBILITY OF PROTEIN SUPPLIED BY PEANUT PRESS-
CAKE FLOUR.
As previously noted on page 13, two types of peanut flour. were
used in these tests, namely, one made by grinding the press cake
resulting from the expression of oil from roasted, degermed peanuts,
and the other by grinding the press cake remaining after the ex-
pression of oil from raw shelled peanuts from which the red skin had
not been removed. The roasted peanut flour was of a golden yellow
color and that from the raw peanuts was of a decidedly red tinge.
Seven experiments were made with flour made from roasted peanuts
and four with flour made from raw peanuts. In the first series of
experiments the ‘‘flour mixture” used for making the biscuits con-
sisted of two parts wheat flour and one part peanut flour (roasted
peanuts), and in the second series the ‘‘flour mixture” consisted of
equal parts of wheat flour and peanut flour (raw peanuts). Since
the same men served as subjects and uniform experimental condi-
tions were maintained for both series, the results obtained should be
directly comparable.
20 BULLEDIN Wii, Wey Se
DEPARTMENT OF AGRICULTURE.
EXPERIMENTS WITH FLOUR MADE FROM ROASTED PEANUTS.
The results obtained in the seven experiments in which peanut
flour made from roasted nuts was studied are reported in the following
tables:
Data of digestion experiments with flour made from roasted peanuts in a simple mixed diet.
Experiments, subjects, and diet.
Experiment No. 618, subject P. K.:
Biscuits containing peanut flour......- 1, 229.0 333.9 | - 168.3 101.5 572.5 52.8
Peanut Oless2s espace oe seiseee see IBGE) |JEdoooodadlicsduscgese A365 Obl 2s ah] eies eens
Bruit. caer sc se sees ceeds Osi sanerace 755.0 656.1 6.0 1.5 87.6 3.8
BUgaT eee ae HOSOD SAE A abo BR oo uUe a Aneee PNY sesso sscbs|[ooosssoocdlseoacdoos+ 4 SIE) SA Se Se oe SS
Total food consumed..............-- 2,401.0 990.0 174.3 239.0 941-1 56.6
GCOS 28 aetio cc cece eax eee sate eee 2M) Nlosooonocas 10.9 6.1 8. 3.6
ATMOUTItAULINZEd geet nee ase ceere reece eer eeeeeeoee 163. 4 232.9 932. 7 53.0
Renicentutilizedseesesceec eee eae es Coeeeceer el eeeeeee ee 93.7 97.4 99.1 93.6
Experiment No. 619, subject J.C. M.:
Biscuits containing peanut flour. ...-- 993.0 269.8 136.0 82.0 462.5 42.7
MPeanubiOile cs eh eciset stamens Saseee CY WH bbesosdasollagoobocddc SONOS ase ee el crs eee
TON eb UD Reta oe toy ue gam dele oe tanned Sh oy A 1,056. 0 917.7 8.4 2.1 122.5 5.3
SURAL ee Sook sec cine eee eteeleiaic cee WYO) |leasdadosasiscosososbsllscacsodoce TRPA OMe SasssGoee
Total food consumed..-.-.-.....-.-.-- 2,330.0 | 1,187.5 144.4] ° 173.1 777.0 48.0
OCS ae Saat eeas ose ELE ERR EP GEO iescsssosee 19.5 8.5 15.5 7.5
ANVTGUEN IF WANE eS OSS SES seo Gop Useosdnd eso soo speleecéadasoc 124.9 164.6 761.5 40.5
iRercentiatilized aana-.sas0-26 cee eens | Saeco ee | eeeeeee nee 86.5 95.1 98.0 84.4
Experiment No. 620, subject C.J. W.:
Biscuits containing peanut flour.....-- 1,188.0 322.8 162.6 98.1 553.4 51.1
IReanwGiOils see es eee aceon sce ek LOO) eye cee eral eeoerseags eee 1990 Wisccistecteciecasaesees
CUD Re eee ae Se ee tae epee se ye ae 751.0 652.6 6.0 1.5 87.1 3.8
SUSATAE: cee yoo ET Sue ee ae DAY CR (ea ee ee NCR he | SEE hte 1642 Ot cesse tes:
Totalfood consumed...........----- 2,302.0] 975.4| 168.6| 298.6] 804.5 54.9
MOCES eA eld ec ete cae Re era p ele ice S050) |lsecosdeuoe 33.3 14.4 21.7 10.6
Amount Utilized. se sence sce es ce eee eee eereale eseeeeer 135. 3 284.2 782.8 d4 3
Pericentiatilized: oe eek as 5 Mee ee leer sees + cerserercr se 80. 2 95. 2 97.3 80.7
Experiment No. 633, subject A. A. F.:
Constituents of foods.
Weight
of foods.
: Carbo-
Water. | Protein. Fat. ‘| hydrates. Ash.
Grams. | Grams. | Grams. | Grams. | Grams. | Grams.
| O_O
Biscuits containing peanut flour...---. 2, 244.0 712. 5 349. 2 114.9 977.0 90. 4
EU Gees ss Soins ook bem wae eee 762. 0 662. 2 6.1 ils & 88. 4 3.8
Peanut. ss sseceeeeee cee sesso ‘OAS Be eme ea seee seer 107. O! | Seeeeee Ee eee
UP AD edie nciabie heeise ees sie erciainaeeee ee DS TN) arate ell ore aioe erkeciss oae PAB) |loeasasasse
Total food consumed............--.- 3,346.0 | 1,374.7 355. 3 223.4 | 1,298.4 94.2
MO COSi2 4 Ses cee aoe eee eS SSS aoe eat PRO O! ease eres 23. 2 11.2 21.6 8.0
AIMOUME Ut Zed eas cthe coe ats seis ees ecieie cette yal cose eee 332. 1 212.2 | 1,276.8 86. 2
Perscont utilized’ | Cees ead en ee ee 93. 5 95.0 98.3 91.5
Experiment No. 634, subject P. K.: -
Biscuits containing peanut flour......- 1, 923.0 610.5 299. 2 98. 5 837. 3 77.5
SEU G he) are sie eae ee ees 485. 0 421.5 3.9 1.0 56. 2 2.4
Reanwtioleg - sas sees meee <a eee 224 1Oiee ater cae atte: 22450) ei See ee eats
UP AT tae arate is eis isrere elec cictenieie ela eoee 167..00/ [3 Re Slee ease feces ae iy COE Reese sacs
Total food consumed............---- 2,799.0} 1,032.0 303. 1 323.5 | 1,060.5 79.9
Wecesten yon acess suck the. ese e eRe P EE 85.0 es. ELLE 27.5 29. 0 8.3 10. 2
ANT UIOH OLA VEY {20 eee I il tee uy tea lsosoudobor 275.6 294.5 | 1,042.2 69.7
Pervcentutilized ss eo eter. eee ee 90.9 91.0 98.3 87.2
Experiment No. 635, subject J. C. M.: 3
Biscuits containing peanut flour...... 1,589.0 504.5 247.2 81.4 691.9 64.0
RUD Gee ee eras seas ajc ack ee sisioemiewne sas 869. 0 755. 2 7.0 a 100. 8 4.3
PeanwtOlle toes ee ee eee 190H0 hein et ee a are ene. 19OKON See eee oaleeet ees
SURAT Mote ele oie mieceneeciceee nae aS fal 0) ae neste Neg eA eo ie ees Sec 1976 Os eee
Total food consumed-2--.----./.-..- 2,845.0 | 1,259.7 254. 2 273.1 989. 7 68.3
MOCOS ee ee eeseece sees ae ke eee’ 4080\|Peee e224: 16.8 5.3 WIS 6. 2
IATHOUN EU LIZ OG Serseers sete cree coe se cee ean Deere 237.4 267. 8 978. 0 62.1
Percent utilized es ycierscatan ccs | octane clea see ae ee 93. 4 98. 1 98.8 90.9
DIGESTIBILITY OF SOY-BEAN AND PEANUT FLOURS. | ye Ens
Data of digestion er RraeUs with flour made from roasted peanuts in a simple mixed
diet—Continued.
Constituents of foods.
Experiments, subjects, and diet. ete ee
f . aT bo-
Water. Protein. Fat. hydrates. Ash.
Experiment No. 636, subject C.J..W.:. | Grams. | Grams. | Grams. | Grams. | Grams. | Grams.
Biscuits containing peanut flour.....-. 1,928.0 612.1 300. 0 98. 7 S3OR ane = leiden:
DM eV TR a hn ee pe TEL I 878.0 763.0 7.0 1.8 101.8 4.4
Peanut oll cs ss. eee we seee ses « 2035 OM el ecien mele | ea eects QOSEOH | Psec eee a eer ee
SuUgaries she ce Sele sas ce Nee ete UAE UES See ae aol ers heres a by a Ares 194.0) teens
Total food consumed..--.......----- 3,203.0} 1,375.1 307. 0 303.5 | 1,135.3 82. 1
OCOS Rpts eins same Heccmie mine srecarsit tee GSHON Eee cean crs 4 10.6 18.0 8.0
ANG O WHA L A Sous canoaoaoodobecaulbeosaudsos Joe eeeeeeee 280. 6 292.9 | 1,117.3 74.1
IRericentaltilized ees eee eee eee | Eee ete | 91.4 96. 5 98. 4 90. 3
Average food consumed persubject perday.| 915.5 | 390.2. | 81.3 S723) |mibasane 23.0
Summary of digestion experiments with flour made from roasted peanuts in a simple
mixed diet.
Digestibility of entire ration. Esti-
: mated
5 digesti-
Experiment No. Subject. rss pity
. arbo- of peanut
Protein. Fat hydrates Ash. protein
alone.
Per cent.| Per cent. | Per cent. | Per cent.| Per cent.
GL Sasso Es ee Oe At Geet ale 2 ve gape 93.7 97.4 99.1 510 93.5
CO AS eM i a ue aaa Se CST Gora pa tere ma 86. 5 95.1 98. 0 84. 4 75.0
4 Das Hs Ao ee dels Cee Wigasns tc tpaee hee 80. 2 95. 2 97.3 80.7 | ° 60. 7
C0 a i ees Nae apes Ber | EAC AC Hetero tabne initia hay ae es dees 93.5 95.0 98. 3 91.5 92.9
CF iS anaes ey eth ag elepe ie a Aa Ce eT oe 0 ae cee 90. 9 91.0 98. 3 87. 2 86. 9
ERY at A MRL RG Nae eka Ae Chard) [eee rt Ree Meee 93. 4 98. 1 98. 8 90. 9 92. 6
6365. ee ee ee N Le ede CWA es il Ae et OO acl 91.4 96. 5 | 98. 4 90. 3 87.9
VANVCHA PCRs uk Main Re MRI ONE AL uh o 89.9 | 95.5 | 98.3: | 88. 4 | 84. 2
On an average the subjects ate 81 grams of protein, 87 grams of fat,
and 334 grams of carbohydrate daily, which supplied about 2,445
calories. The coefficients of digestibility of these constituents sup-
plied by the diet as a whole were found to be 89.9 per cent for pro-
tein, 95.5 per cent for fat, and 98.3 per cent for carbohydrate, indi-
cating that the diet was quite well utilized. The above value for the
digestibility of the total protein of the diet becomes 84.2 per cent
for the digestibility of peanut protein alone when correction is ap-
plied for the undigested protein occurring in the accessory foods.
The diet as a whole supplied 81 grams of protein daily, of which 79
grams were derived from the peanut-flour biscuits, and approxi-
mately 34 grams were obtained from the peanut flour. No physio-
logical disturbances were noted by any of the subjects, indicating
that this amount of peanut protein was well tolerated in these
experiments.
In this series of experiments the subjects ate on their biscuits in
place of butter peanut oil which was expressed from the blanched
yap. BULLETIN 717, U. S. DEPARTMENT OF AGRICULTURE.
peanuts from which the peanut flour was prepared. The average
amount eaten was 55 grams daily; and apparently it was well
digested, since the total fat of the diet—principally lard and peanut
oil—was 95.5 per cent digested. This compares very favorably with
the figures reported for tho digestibility of lard ‘ and peanut oil? as
determined in earlier studies.
EXPERIMENTS WITH FLOUR MADE FROM RAW PEANUTS.
The data resulting from the four experiments made with peanut
flour made from raw peanuts are summarized in the table which
follows:
Data of digestion experiments with flour made from raw peanuts in a simple mixed diet.
| : Constituents of foods.
Experiments, subject, and dict. Weleht
of foods. : ne eae
Water. rotein. Fat. | hydrates. Ash.
CeQD crea) eters (ego st peer SAIL CY |
Experiment No. 696, subject P. K.: | Grams. | Grams. | Grams. | Grams. | Grams, | Grams
Biscuits containing peanut flour. PSA.)
Butter ---:-.-------2222-=------------=
WOCESE Vn co eee a ee eae oe ee
iPernicenti utilized tat S255 ses eee ee see eee ccsreloceseeeses
Experiment No. 697, subject J. C.
Biscuits containing peanut Mate eee
Butter .-..-.--------------------------
Experiment No. 698, subject A. A. R.:
Biscuits containing peanut flour.._....
Butter. -......-------------------+---- |
Total food consumed..............-.
Meces. 5 eb se SES
AMOUNT ULINIZed ee ee ae eee ee
‘Per cent 1itilized:. 2 eo ee ee ala eee | eee
Experiment No. 699, subject W. E. T.:
Biscuits containing peanut flour.....-.
Butter. ...-..-...---.-------------- me
GERY Ss cone scoossscosessocesceossseosesooc * 835. 9 364. 3 | 105. 5 117.1 224. 1 | 25. 0
1U.S. Dept. Agr. Bul. 310 (1915), p. 21. 2U.S. Dept. Agr. Bul. 505 (1917), p. 18.
DIGESTIBILITY OF SOY-BEAN AND PEANUT FLOURS. 23
Summary of digestion experiments with flour made from raw peanuts in a simple mixed
diet.
Digestibility of entire ration. Esti-
ieied
5 igesti-
Experiment No. Subject. bility
i Carbo- of peanut
Protein. | Fat. hydrates.| Ash. protein
alone.
Per cent. | Per cent.| Per cent.| Per cent.| Per cent.
91.0 97.0 97.3 86. 4 89. 4
6968 oe Sse ak Sees IPG Ses cc kaos ioe Ses
GOT fea ates tee JE CRMD es astise satis sscccee 89.7 97.9 96. 4 91.7 87.6
(ee seao8 seocsssehoocs- some JAK Jas Liat Soe oo sage Oaan 89. 6 96. 2 96. 9 84.6 87.3
idesebsese dao tees sesece6 Witte nroee te ciate oat a= 91.4 95. 0 98.1 85.9 90.5
Average.....-------|------ +--+ +2222 eee ee eee eee 90. 4 96.5 97.2 87.2 88.7
As indicated by the above table the subjects ate on an average
106 grams of protein, 117 grams of fat, and 224 grams of carbohy-
drate daily, which supplied approximately 2,370 calories. The
average coefficients of digestibility of the protein, fat, and carbohy-
drate supplied by the diet as a whole were 90.4 per cent for the pro-
tein, 96.5 per cent for the fat, and 97.2 per cent for the carbohy-
drates.
Of the average amount of protein eaten daily (106 grams), 103
grams were supplied by the peanut biscuits, 65 grams being con-
tributed by the peanut flour. This amount of peanut protein, much
larger than that likely to be found in the ordinary mixed diet, was
eaten without any noticeable digestive or other disturbances.
The digestibility of the peanut protein alone, estimated for pea-
nut flour made from raw nuts, was found to be 88.7 per cent, a
value which is not significantly different from the value (84.5 per
cent) found for the proteins supplied by peanut flour made from
roasted nuts. Accordingly it would appear from these figures and
from the figures given above for the protein, fat, and carbohydrate
of the peanut-cake diet as a whole that neither roasting nor the pres-
ence of the peanut skin materially affected the thoroughness of
digestion.
SUMMARY OF ALL EXPERIMENTS WITH PEANUT FLOURS.
In order to compare carefully the values for the digestibility of
protein, fat, and carbohydrate supplied by simple mixed diets, which
include peanut flours ground from cakes from roasted and from raw
peanuts, the results which have been obtained in the two series of
experiments here reported have been brought together in the table
following.
94 BULLETIN 717, U. S. DEPARTMENT OF AGRICULTURE.
Summary of digestion experiments with flour made from peanuts in a simple mixed diet,
Esti
{ mated
Experl- aia : ; Garo digesti-
men Kind of peanut flour. Subject. Protein.| Fat. Herdeates Ash. | bility of
No. y i peanut
protein
alone
|
Per cent.| Per cent.| Per cent. |Per cent.| Per cent.
Olseeee Flour from roasted nuts...... Ag CE CSIR aa 93. 97.4 99.1 93.6 93.5
GG ces eee GOs en gee els heyetnlee ra AEX Oia bese ie es 86. 95.1 98.0 84.4 75.0
PHD salladeee GOR SG SEGUE Sal weD 8s OATUIWE Baa 80.2 95. 2 97.3 80.7 60.7
G33raeEe AOE KG oye Neos ie Uae career TAR WAL TLS Vs Shi 93.5 95.0 98.3 91.5 92.9
GB AR ISS yee Oe BU UD iL ok AD aie aa 1 Eo Yl Si pete irs ce ER 90.9 91.0 98.3 87.2 86.9
OB al ese (6 Lo Vel a Ree Ws RR el AE Se A [eal ris) ape eas 93.4 98.1 98.8 90.9 92.6
CSOs rani GOES INR NO EA RARE IN CH TEAWH a Mae 91.4 96.5 98. 4 90.3 87.9
PANSY CTA SCN a1!) AG UE PAN ey 89.9 95.5 98.3 88.4 84.2
696....- Flour from raw nuts......... TRO set Nee 91.0 97.0 97.3 86.4 89.4
COT ee eae OHA BOR Mee EO a RC OER TCM ee 89.7 97.9 96. 4 91.7 87.6
GOS ME eel ae CG Ua yeR ea A ac UGS Co ea tes VA ACR See ae 89.6 96. 2 96.9 84.6 87.3
Oe) Ae a COR eT ANE bE eee Wie ean 91:4 95.0 | 98.1 85.9 90.5
AV GrAgerrrians of tk BORIS ARMR A ANG I - 90.4 96.5 | =F 9712) S719 | Eee.
Average of all tests..... AERA LG 90.1| 95.9 | 97.9] 87.9 85.8 -
Considering the experiments with peanut flour as a whole it would
seem fair to assume that the average data obtained for the digesti-
bility of peanut protein should be sufficient for quite general appli-
cation, since a total of eleven different tests was made with six dif-
ferent subjects and two different types of peanut flours. Considering
the ration as a whole or considering the peanut protein alone, the
coefficients of digestibility obtained with the two types of peanut
flour are in close agreement. The average coefficients of digesti-
bility for the diet as a whole—90.1 per cent for protein, 95.9 per cent
for fat, and 97.9 per cent for carbohydrates—indicate that the experi-
mental diet was, for all practical purposes, as well utilized as the
ordinary mixed diet, the coefficients of digestibility ! of which have
been found to be 92 per cent for protein, 95 per cent for fats, and 97 per
cent for carbohydrates. These figures would seem to indicate that
peanut flour is itself well assimilated and that it did not exert any
unfavorable effects upon the digestibility of the other foods included
in the diet.
Comparing the average values obtained for the digestibility of
peanut protein alone in the individual experiments it is found that
peanut protein is 85.8 per cent digested, a figure lower than that of
milk, meat, or egg proteins, about equal to those of cereal proteins,
and somewhat higher than that of the common legumes, From the
previously published data summarized above and the results of these
experiments it appears that the peanut supplies a protein which
yields essential amino acids, is well tolerated by the human body,
and is very well digested. In view of these facts it seems that peanut
flour prepared from high-grade press cake may well assume an im-
portant réle in the human dietary.
1U.S. Dept. Agr. Bul. 142 (1902), p. 26.
DIGESTIBILITY OF SOY-BEAN AND PEANUT FLOUBRS. 25
GENERAL CONCLUSIONS REGARDING THE VALUE OF SOY BEAN AND
PEANUT FLOURS AS FOOD.
Soy beans and peanuts are classed as a ‘‘sure crop,” and both
yield valuable products (press cakes) whose chief use at present is
said to be for stock feeding. The boll weevil has made the growing
of cotton unprofitable in some sections of the South. As a result,
during the last season or two, the culture of soy beans and peanuts
has increased with unusual rapidity. This situation, coupled with
the present great demand for oils, has caused many of the cotton-
seed-oil millers to utilize their machinery for pressing soy beans and
peanuts. The resulting soy-bean and peanut press cakes when
ground yield a flour very rich in protein and, as compared with
cereal flours and meals, fairly rich in fat. ;
Chemical analyses reported by previous investigators of glycinin
and arachin, soy-bean and peanut proteins, show that both, by hy-
drolysis, yield lysine and tryptophane, two amino acids recognized
as essential for growth and maintenance.
Investigators studying the biologic value of these proteins by ex-
periments with laboratory animals have shown that soy-bean and
peanut proteins when employed as the sole source of protein in an
otherwise adequate diet support in a satisfactory manner the normal
body processes of growth, maintenance, and reproduction.
In view of these facts it seemed highly desirable to study the diges-
tibility of the proteins supplied by soy-bean and peanut flours pre-
pared by grinding press cakes obtained by the expression of oil from
clean sound soy beans and peanuts.
The experiments here reported were made with normal young men
students engaged in moderately active pursuits. The soy-bean and
peanut flours were eaten in the form of a well-known type of ‘‘quick
bread” or ‘‘biscuit’’ as a part of a simple mixed diet. None of the
subjects reported any digestive or other physiological disturbances
in connection with these diets, indicating that as regards the time
and method of cooking, the soy-bean and peanut flours were satis-
factory.
The figures, 85 per cent for the digestibility of soy-bean protein
contained in ground cake and 86 per cent for the digestibility of
peanut proteim present in ground cake, indicate a very satisfactory
utilization of these proteins by the human body. If allowance has
been made for that portion of the fecal nitrogen which resulted from
epithelial cells and bacteria instead of including it in the undigested
residues of the soy beans and peanuts, the coefficients of digestibility
of soy-bean and peanut proteins would have been somewhat higher.
The figures obtained for the digestibility of the proteis supplied
by soy-bean and peanut press-cake flours compare very favorably
with those obtained for cereal proteins and are somewhat higher than
26 BULLETIN 717, U. S. DEPARTMENT OF AGRICULTURE.
those obtained for some other legume proteins. Perhaps the differ-
ence between the digestibility of the soy-bean and peanut proteins
as shown by these experiments and the digestibility of the common
legumes reported by other investigators is due in part at least to
the soy bean and peanut having been finely ground. It is hoped
that additional experiments will give more data on this point.
No attempt was made to ascertain the limit of tolerance for soy-
bean and peanut flours when included in a simple mixed diet, but
since in seven experiments with soy beans the subjects ate an average
of 70 grams daily of soy-bean protein and in four experiments with
peanut flour the subjects ate an average of 65 grams of peanut pro-
tein daily without any observed symptoms of physiological disturb-
ance, it should be very evident that these proteins are tolerated by
the human body in amounts in excess of those which are likely to be
found in the ordinary mixed diet.
Since in household economy the soy-bean and peanut flours would -
be used to supplement wheat or other cereal flours, and since numer-
ous investigations of the value of soy-bean and peanut proteins for
food purposes indicate that these proteins have a nutritive value
nearly if not quite equivalent to that of meat, milk, and egg pro-
teins, it would seem that these flours could be very properly classed
as both wheat and meat substitutes.
From these facts it is very evident that it is highly desirable to use
for human food such soy-bean and peanut press cakes, by-products
of the oil mills, as can be properly prepared for food purposes rather
than to continue to use them exclusively for stock feeding and ferti-
lizing purposes.
The data obtained in this and other investigations give sufficient
evidence to justify the belief that soy-bean and peanut flours, rich in
proteins that are well digested and of high biologic value, should
prove especially valuable additions to the human dietary.
PUBLICATIONS OF U. S. DEPARTMENT OF AGRICULTURE RELATIVE TO
FOOD AND NUTRITION.
AVAILABLE FOR FREE DISTRIBUTION BY THE DEPARTMENT.
Meats: Composition and Cooking. By Chas. D. Woods. Pp. 31, figs. 4. 1904.
(Farmer’s Bulletin 34.)
The Use of Milkas Food. By R.D. Milner. Pp.44. 1911. (Farmers’ Bulletin 363.)
Care of Food in the Home. By Mrs. Mary Hinman Abel. Pp. 46, figs. 2. 1910.
(Farmers’ Bulletin 375.)
Economical Use of Meat in the Home. By C. F. Langworthy and Caroline L. Hunt.
Pp. 30. 1910. (Farmers’ Bulletin 391.)
Cheese and Its Economical Uses in the Diet. By C. F. Langworthy and Caroline L.
Hunt. Pp. 40. 1912. (Farmers’ Bulletin 487.)
Mutton and Its Value in the Diet. By C. F. Langworthy and Caroline L. Hunt.
Pp. 32, figs. 2. 1913. (Farmers’ Bulletin 526.)
The Detection of Phytosterol in Mixtures of Animal and Vegetable Fats. By R. H.
Kerr. Pp. 4. 1913. (Bureau of Animal Industry Circular 212.)
Some American Vegetable Food Oils, Their Sources and Methods of Production.
By H.S. Bailey. (Yearbook Separate 691.)
FOR SALE BY THE SUPERINTENDENT OF DOCUMENTS, GOVERNMENT PRINTING
OFFICE, WASHINGTON, D. C.
Studies on the Influence of Cooking upon the Nutritive Value of Meats at the Univer-
sity of Illinois, 1903-4. By H.S. Grindley, Sc. D.,and A. D. Emmett, A.M. Pp.
230, tables 136. 1905. (Office of Experiment Stations Bulletin 162.) Price, 20
cents.
Studies of the Effect of Different Methods of Cooking upon the Thoroughness and
Ease of Digestion of Meats at the University of Illinois. H. 8S. Grindley, Sc. D.,
Timothy Mojonnier, M. S., and Horace C. Porter, Ph. D. Pp. 100, tables 38.
1907. (Office of Experiment Stations Bulletin 193.) Price 15 cents.
Digestibility of Some Animal Fats. By C. F. Langworthy and A. D. Holmes. Pp.
23. 1915. (Department Bulletin 310.) Price, 5 cents.
Digestibility of Very Young Veal. By C. F. Langworthy and A. D. Holmes. Pp.
577-088. 1916. (Journal of Agricultural Research, 6 (1916), No. 16.) Price,
5 cents.
Digestibility of Hard Palates of Cattle. By C. F. Langworthy and A. ID. Holmes.
Pp. 641-648. 1916. (Journal of Agricultural Research, 6 (1916), No. 17.) Price,
5 cents.
Fats and Their Economical Use in the Home. By A. D. Holmes and H. L. Lang.
Pp. 26. 1916. (Department Bulletin 469.) Price, 5 cents.
Studies on the Digestibility of the Grain Sorghums.. By C. F. Langworthy and A. D.
Holmes. Pp. 30. 1916. (Department Bulletin 470.) Price, 5 cents.
Digestibility of Some Vegetable Fats. By C. F. Langworthy and A. D. Holmes.
Pp. 20. 1917. (Department Bulletin 505.) Price, 5 cents.
Studies on the Digestibility of Some Animal Fats. By C. F. Langworthy and A. D.
Holmes. Pp. 20. 1917. (Department Bulletin 507.). Price, 5 cents.
‘Experiments in the Determination of the Digestibility of Millets. By C. F. Lang-
worthy and A. D. Holmes. Pp. 11. 1917. (Department Bulletin 525.) Price,
5 cents.
27
= '
28 BULLETIN 717, U. S. DEPARTMENT OF AGRICULTURE.
Digestibility of Dasheen. By C. F. Langworthy and A. D. Holmes. Pp. 12. 1917.
(Department Bulletin 612.) Price, 5 cents.
Studies on the Digestibility of Some Nut Oils. By A. D. Holmes. Pp. 19. 1918.
(Department Bulletin 630.) Price, 5 cents.
Experiments on the Digestibility of Fish. By A. D. Holmes. Pp. 15. 1918. (De-
partment Bulletin 649.) Price, 5 cents. ve
Digestibility of Some Seed Oils. By A. D. Holmes. Pp. 20. 1918. (Department
Bulletin 687.) Price, 5 cents. ‘
ADDITIONAL COPIES
OF THIS PUBLICATION MAY BE PROCURED FROM
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