digestibility of raw corn, potato, and wheat · digestibility of raw corn, potato, and wheat ......

DIGESTIBILITY OF RAW CORN, POTATO, AND WHEAT STARCHES.*

BY C. F. LANGWORTHY AND HARRY J. DEUEL, JR.

(From the O&e of Home Economks, States Relations Service, United States Department of Agriculture, Washington.)

(Received for publication, February 26,192O.)

INTRODUCTION.

It has been generally believed that raw starches are only digested a little, if at all, by the human body. Thorpe’ quoting from Roberts says that starch in a raw state “is to man an almost indigestible substance, but when previously subjected to the operation of cooking it is digested with great facility.” He further states that “diastase has, at best, only a comparatively feeble action on the unbroken starch granule, even at the tem- perature of the body.”

Little experimental evidence is to be found regarding the digestibility of raw starches by the human body. Fofanow2 conducted a series of experiments on human subjects with small quantities of raw wheat, oat, rice, and potato starches. He found that raw wheat, oat, and rice starches were practically completely assimilated, while raw potato starch was from two and one-half to four times less well digested. However, in his tests he used only 50 gm. of raw starch, a quantity which might easily be lost in the digestive tract. Numerous artificial digestion experiments have been conducted on raw starches which in general have demonstrated that raw starches are much more slowly acted on by the digestive ferments than starches which have been cooked.3

*Published with permission of the Secretary of Agriculture. 1 Thorpe, E., A dictionary of applied chemistry, London, New York,

Bombay, and Calcutta, 1913, v, 179. 0 Fofanow, L., 2. Min. Med., 1911, lxxii, 257. 8 Day, E. A., U. S. Dept. Agric., Bull. 202, 1908.

27

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28 Digestibility of Starches

EXPERIMENTAL.

The methods in the experiments with corn, wheat, and potato starches were practically the same as in previous digestion experiments conducted by this oflice. In order that the starch should be in an appetizing form, it was eaten as a constituent of a frozen pudding. This was palatable and the subjects were able to eat it in fairly large quantities.

The frozen pudding contained approximately 20 per cent of raw starch and resembled ordinary ice-cream in taste and texture. This method of preparation did not affect the starch granules which were found by the Microchemical Laboratory of the Bureau of Chemistry to be neither swollen nor broken. The pudding was made as follows:

Experimental Frozen Pudding.

6 quarts milk. 2; cups sugar. 4 pounds raw starch. 1 tablespoon salt. 3 cups table oil. $ cup lemon extract.

The uncooked starch was mixed with milk, sugar, and oil in the propor- tions given above and the mixture immediately frozen in the same way as ice-cream. The lemon extract used for flavoring masked to a great extent the taste of uncooked starch and gave the frozen pudding a pleasing flavor.

The subjects were given weighed portions of the frozen pudding along with a basal ration of oranges and sugar. Tea or coffee was used if desired. The experiments were of 3 days or nine meals duration. The subjects were students in a local university who were apparently in normal health. They were familiar with this type of work, having served as subjects in previous experiments, and were entirely trustworthy. The methods for the separation of feces, analyses, etc. were those usually followed.

Corn-Starch.

Three experiments were conducted with raw corn-starch. The essential data for the interpretation of the results of these experiments are given in Tables I and II.


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TABLE I.

Digestion Experiments with Uncooked Corn-Starch in a Simple Mixed Diet.

Experiment, subject, Weight o and diet. food.

Experiment No. 1047 Subject W. V. D.

Frozen custard containing uncooked starch (= 67 per cent total carbohydrate = 644 gm.), gm.. . . .

Fruit, gm.. . . . . . . . . Sugar, gm.. . . . .

3,365.C 818.C 138.C

Total food con- sumed, gm.. . . 4,321.C

Feces, gm.. . . . . . Amount utilized,

gm.. . . . . . . . . , . . . Digestibility of en-

tire ration, per cent., . . . . . . , , . .

Estimated digestibility of uncooked starch alone, per cent..

76.C

Experiment No. 1048 Subject H. L. G. :

Frozen custard containing uncooked starch (= 67 per cent total carbohydrate = 773 gm.), gm... . . . . . .

Fruit, gm.. . . . . . . . . Sugar, gm.. , . . . . . . .

&038.0 1,193.o

62.0

Total food con- sumed, gm.. . . . . 5,293.O

Feces, gm.. . , , . . . . . Amount utilized,

gm.. . . . . . . . . . . . . .

Constituents of foods.

water. Protein. Fat.

2,030.l 710.1

2,740.g

76.4 277.3 6.6 1.6

83.0

21.6

61.4

278.9 lJ94.3

$436.1 .,036.7

J472.8

Zarbohy- drate. Ash.

961.4 94.9

138.0

19.8 4.1

30.5 10.2

248.4 1,184.l

23.9

13.7

10.2

74.0 89.1 99.1 42.7

100.0

91.7 9.5

101.2

332.7 2.4

1,153.7 138.4 62.0

23.8 6.0

335.1 1,354.l

19.7 10.8

315.4 1,343.3

29.8

15.8

85.4

-i-

8.7

21.1

29


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Digestibility of entire ration, per cent. . . . . . . .

Estimated digestibility of uncooked starch alone, per cen.t. .

Experiment No. 1049, Subject E. L.M.:

Frozen custard containing uncooked starch (= 67 per cent total carbohydrate = 751 gm.), gm... . . .

Fruit, gm.. . . . . Sugar, gm.. . . .

Total food con- sumed, gm.. . .

Feces, gm.. . . . Amount utilized,

gm.. . . . . . . . . . Digestibility of en-

tire ration, per cent.. . . . . . . . . .

Estimated digestibility of uncooked starch alone, per cent..

Average food con- sumed per subject per day, gm.

TABLE I-concluded.

ght of md.

j24.0 L27.0 31.0

B2.0

51.0

I water. Protein. Fat.

84.4 94.1

Z,367.3 89.1 323.3 979.4 9.0 2.3

3,346.7

1,062.3


98.1

14.8

83.3

84.9

31.4

:arbohy- drate. Ash.

- -

99.2

100.0

70.8

1,121.1 130.7

31.0

23.2

5.6

325.6 1,282.g 28.8

14.9 15.0 6.3

310.7 lJ67.8 22.5

95.4

104.4

98.8

100.0

425.7

78.1

9.2


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C. F. Langworthy and Harry J. Deuel, Jr. 31

The diet as a whole supplied on an average 31 gm. of protein, 104 gm. of fat, 426 gm. of carbohydrate, and had an average energy value of 2,760 calories per man per day. The average amount of raw corn-starch eaten per man per day was 241 gm. Subject H. L. G. in Experiment 1048 ate the maximum amount of raw corn-starch which was 258 gm. per day for the experimental period.

The coefficient of digestibility of the raw corn-starch was found in each case to be 100 per cent after correction is made for

TABLE II.

Summary of Digestion Experiments with Uncooked Corn-Starch in a Simple Mixed Diet.

1047 1048 1049

T

I Digestibility of entire ration.

Subject. 1 Protein. 1 Fat. 1 “$?$‘$I Ash.

per cent prr cent per cent per cent

W. V. D. 74.0 89.1 99.1 42.7 H. L. G. 84.4 94.1 99.2 70.8 E. L. M. 84.9 95.4 98.8 78.1

Average . . . . . . . . . /81.1192.9~Qs.o163.n

Estimated digestibility of

uncooked corn-starch

&Ile.

per cent 100.0 100.0 100.0

100.0

the undigested residue from the accessory foods. This was con- firmed by the Microchemical Laboratory of the Bureau of Chem- istry which reported that no unruptured starch grains could be detected in the feces and that the iodine test for starch in the feces was negative.

The ingestion of this frozen custard caused no noticeable phys- iological effects and the subjects were in normal health during the experimental period. They reported the diet as appetizing and satisfying, a fact which would indicate that the starch was assimilated to a great extent by the body.

Potato Xtarch.

Seven experiments were conducted with potato starch-two in one test and five in a second test a few weeks later. The two subjects who took part in the first test had taken part in the experiments with raw corn-starch. In the second test with raw potato starch these men were joined by three others, one of whom had taken part in the experiments with raw corn-starch.


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Tables III and IV are a summary of the results of the experiment,s with raw potato starch.

The diet as a whole furnished on an average 23 gm. of protein, 76 gm. of fat, 357 gm. of carbohydrate, and had an average energy value of 2,213 calories per man per day. The average amount of starch eaten per man per day was 194 gm.

It will be noted from Tables III and IV that the amount of potato starch digested varied considerably with the different subjects and even with the same subject in successive periods. Subject J. F. S. in Experiment 1082 showed the highest coefficient of digestibility (95.2 per cent) while Subject E. L. M. in Experi- ment 1081 showed the lowest (62.3 per cent) Subject H. L. G. in the first test ate 573 gm. of raw starch of which 74.5 per cent was digested. In the second test the digestibility increased to 85.4 per cent despite the fact that 120 gm. more of potato starch were eaten than in the first. On the other hand, Subject E. L. M. in the first test ate 503 gm. of raw potato starch of which 74.3 per cent was digested while in the second test only 62.3 per cent of the 710 gm. eaten was digested. There seemed to be no definite relation between the amount eaten and the amount digested A possible explanation of the variation in the ability of the various subjects and of the same subjects in different periods to digest the raw potato starch may be that the body was unable to supply a large enough amount of amylases in a given time to digest all the raw starch.

During this diet practically all the subjects noted a very exces- sive formation of gas and frequent intestinal cramps. The quan-- tity of feces voided was very large; a large amount of undigested starch was visible and a strong positive reaction was given with iodine. When the feces were ashed, the odor resembled that of scorched bread and no fecal odor was evident. The figure for the digestibility of protein is probably too low, since only a small amount was eaten and no correction has been made for metabolic nitrogen in the feces. The coefficient of digestibility for the cream and corn oil was 95.7 per cent. This agrees closely with previous determinations by this office which were 96.g4 per cent. for cream and 97.g5 per cent for corn oil.

4 Langworthy, C. F., and Holmes, A. D., U. S. Dept. Agric., States Relations Service, Bull. 607, 1917.

6 Holmes, A. D., U. S. Dept. Agric., States Relations Service, Bull. 687, 1918.


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TABLE III.

Digestion Experiments with Uncooked Potato Starch in a Simple Mixed


Protein Fat.

60.7 216.4 7.3 1.8

816.: 105.C 68.C

Experiment, subject, and diet. w%%.a -

-_

,

--

.-

--

-

990.4

water.

Experiment No. 1062, Subject H. L. G. :

Frozen custard containing 572.6 w. uncooked starch, gm.. . . . . .

Fruit, gm.. . . . . . . . . 8ugar, gm.. . . . . . . .

1,707.E 793.4

2,823.C 913.c 68.C

3,804.C 1,501.2

21.6 4.6

26.2

7.6 18.6

71.0

19.0 3.6

Total food con- sumed, gm.. . . 68.0 218.2

Feces, gm.. . . . . . . . . Amount utilized, gm. Digestibility of en-

tire ration, per cent.. . . . . . . . . . . . . . .

Estimated digesti- bi1it.y of uncooked starch alone, per cent.. . . . . . . . . . . . . . .

Experiment No. 1063, Subject E. L. M. :

Frozen custard containing 502.8 gm. uncooked starch, gm.. . . . . .

Fruit, gm.. . . .., . . . . Sugar, gm.. . . . . . . . .

17.3 6.1 163.C 50.7 212.1 827.4

74.6 97.2

53.7 5.8

191.5 1.5

83.4

74.5

718.3 84.1

105.0

907.4

194.c

?,491.0 725.0 105.0

1JO8.5 630.0

$321.0 $138.5

191.0

Total food con- sumed, gm.. . . . 193.0 59.5

27.8 31.7

53.3

22.6

Feces, gm.. . . . . . . . . . . Amount utilized, gm.. Digestibility of en-

tire ration, per cent.. . . . . . . . . . . . . . .

Estimated digestibility of uncooked starch alone, per cent. . . . . . . . . . . . . . . .

10.7 182.3

94.5


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Digestibility of Starches

TABLE III-Continued.

Experiment No. 1078, Subject P. C.:

Frozen custard containing 467.7 gm. uncooked starch, gm.. . . . . . .

Fruit, gm.. , , .., . . . Sugar, gm.. . . . . . . . .

Total food con- sumed, gm.. . . .

Feces, gm.. . . . . . . . . . . Amount utilized, gm. Digestibility of en-

tire ration, per cent. . . . . . . . . . . . . . . .

Estimated digestibility of uncooked starch alone, per cent. . . . . . . . . . . . . . . ,

Experiment No. 1079, Subject W. V. D. :

Frozen custard containing 544.8 cm. uncooked starch, gm., . . . . . .

Fruit, gm.. . . . . . . . . . Sugar, gm.. . . . . . . .


Feces, gm.. . . , . . . . . . Amount utilized, gm.. Digestibility of en-



2,505.o 1,372.O

183.0

$060.0

243.0

Z,918.0 807.0

97.0

3,822.0

105.0

-

_-

: -

1

.-

:

-

water.

1,553.l 51.6 184.6 1,192.3 11.0 2.7

q745.4 62.6

1,809.2 60.1 215.1 701.3 6.5 1.6

!,510.5


Protein.

28.9 33.7

187.3

11.0 176.3

191.4 11.7 848.9 12.7

53.8 94.1 81.6 52.0

64.3

813.2 93.6 97.0

20.4 4.0

66.6 216.7 1,003.8 24.4

21.9 10.8 64.1 8.2 44.7 205.9 939.7 16.2

67.1 95.0 93.6 66.0

Fat. %!2 r .

698.2 159.1 183.0

1,040.3

91.3

Ash.

17.5 6.9

24.4


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C. F, Langworthy and Harry J. Deuel, Jr. 35

Experiment No. 1080, Subject H. L. G.:


Fruit, gm.. . . . . . . . . . Sugar, gm.. , . . . . . . .

Total food con- sumed, gm.. . . . .

Feces, gm.. . . . . . . . . . . Amount utilized, gm. Digestibility of en-


Estimated digestibility of uncooked starch alone, per cent.. . . . . . . . . . . . . . .

Experiment No. 1081; Subject E. 1,. M. :


Fruit, gm.. . . . . . . . . . Sugar, gm.. . . . . . . . .

Total food con- sumed, gm.. . . . .




TABLE III-continued.

1,703.C 731.C

43.C

L,477.(

149.C

1,803.C 526.C 105.c

L,434.C

332.C

- I Constituents of foods.

Water.

$295.9 635.2

!,931.1

!,357.8 457.1

T

. _

.-

.-

- !,814.9

Protein. Fat. Ash.

76.3 5.8

272.9 1.5

1,032.O 84.8 43.0

25.9 3.7

82.1 274.4 L,159.8 29.6

18.2 7.3 117.4 6.1 63.9 267.1 lJI42.4 23.5

77.8 97.3 89.9 79.2

35.4

78.3 4.2

280.3 1.1

1,059.g 61.0

105.0

26.7 2.6

82.5 281.4 1,225.g

27.4 11.6 283.2 55.1 269.8 942.7

66.8 95.9 76.9

-

62.3

29.3

9.8 19.5

66.6


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TABLE III-concluded.

Constituents of foods Experiment! subject,

and diet.

3,107.o 1,324.0

166.0

-

.-

--

.-

--

Water. Ash. Zarbohy- drate.

865.9 153.6 166.0

Protein. Fat.

1,926.3 64.0 1,150.6 10.6

229.0 2.6

3,076.g 74.6

24.3 50.3

231.6

8.9 222.7

1,185.5

52.1 1,133.4

67.4 96.2 95.6

95.2

891.4 23.6 76.3 357.8

Experiment No. 1082, Subject J. F. S.:

Frozen custard containing 580.1 w. uncooked starch, gm.. . . . .

Fruit, gm.. . . . , . . . Sugar, gm.. . . . . , . .

21.5 6.6


Feces, gm.. . . : . . . . . . Amount utilized, gm. Digestibility of en-

tire ration, per cent. . . . . . . . . . . . . . .

Estimated digestibility of uncooked starch alone, per cent. . . . . . . . . . . . . . .

Average food con- sumed per subject per day, gm.

28.4 $597.0

100.0

1,357.g

14.7 13.7

48.1

8.8

TABLE IV.

Summary oj Digestion Experiments with Uncooked Potato Starch in a Simple Mixed Diet.

Digestibility of entire ration. Estimated digestibility of

uncooked Potato~arch

Subject. :arbohy

drate. Ash.

pm cent per cent pm cent

83.4 71.0 74.5 84.1 61.9 74.3 81.6 52.0 64.3 93.6 66.0 91.3 89.9 79.2 85.4 76.9 66.6. 62.3 95.6 48.1 95.2

86.4 63.5 78.2

Protein. Fat.

1062 H. L. G. 1063 E. L. M. 1078 P. c. 1079 W. V. D. 1080 H. L. G. 1081 E. L. M. 1082 J. F. S.

per cent 74.6 53.3 53.8 67.1 77.8 66.8 67.4

Average . . . . . . . . . . . . . . . 65.8

pe? cent 97.2 94.5 94.1 95.0 97.3 95.9 96.2

95.7

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TABLE V.

Digestion Experiments with Uncooked Wheat Starch in a Simple Mixed Diet.

Experiment No. 1073, Subject P. C.:

Frozen custard containing 462.4 w uncooked starch, gm.. , . . . . .

Fruit, gm.. . . . . . . . . . . Sugar, gm.. . . . . . . . .




Estimated digestibility of uncooked starch alone, per cent.. . . . . . . . . . . . . . .

Experiment No. 1075, Subject H. L. G. :

Frozen custard containing 692.7 gm. uncooked starch, gm.. . . . . .

Fruit, gm.. . . . . . . Sugar, ‘gm.. . . . . .


Feces, gm.. . . . . . . . . Amount utilized, gm. Digest,ibility of en-

tire ration, per cent. . . . . . . . . . . . .

Estimated digestibility of uncooked starch alone, per cent.. . . . . . . . . .

-

V

-

:

.-

: .-

!,493.0 728.0 120.0

J341.0

31.0

3,734.c 597.c

8.C

4,339.c

56.C

I- -

--

3

--

: --

1 :

1

1 --

) : --

)

-

water. Protein. Fat.

.,573.3 48.4 164.8 632.6 5.8 1.5

!,205.9 54.2 166.3 894.8

5.1 5.7 16.5 49.1 160.6 878.3

90.6 96.6 98.2 81.3

6,356.5 72.4 246.8 518.8 4.8 1.2

2,875.3 77.2 248.0

37


4.5 17.9 72.7 230.1

94.2 92.8 97.E

:arbohy- drate.

690.3 84.5

120.0

99.8

1,034.c 69.2 8.C

lJ11.2

23.3 1,087.F

98.F

-

_-

_-

Ash.

16.2 3.6

19.8

3.7 16.1

24.3 3.0

27.3

10.2 17.1

62.6


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TABLE v-Concluded.


3,223.l 1,294.1

201.1

2,034. C 1,124.5

4,718.I 3,158.5

68.1

>f -

--

0 :

0

0 --

0 : --

0

0

0 0 -.

0 : --

0

--

) -

Water. Protein. Fat.

2,743.1 1,115.l

172.1

1,731.l 968.E

4,030.l 2,700.c

22.1

1,369.C 911.6 22.2

:arbohy drate.

62.5 213.0 10.3 2.6

72.8 215.6

6.1 17.6 66.7 198.0

91.6 91.8

-

_-

_-

Ash.

892.5 150.1 201.0

21.0 6.5

1,243.g

33.5 1,210.l

97.3

27.5

10.8 16.7

60.7

98.4

53.2 181.3 8.9 2.2

759.6 129.4 172.0

17.8 5.6

--

62.1 183.5 1,OGl.O 23.4

4.3 57.8

2.2 21.2

93.1

10.5 .5 0

173.0 1,056.O

94.3 99.5 90.6

100.0

67.8 359.2

-

- 8.2

Experiment No. 1076, Subject E. I,. M. :

Frozen custard containing 597.9

gm. uncooked starch, gm.. . . . .

Fruit, gm.. . . . . . . . . Sugar, gm.. . .

Total food con- sumed, gm.. .

Feces, gm.. . . . . . . Amount utilized, gm. Digestibility of en-

tire ration, per cent Estimated digesti-

bility of uncooked starch alone, per cent. . . . . . . . . . . .

Experiment No. 1077, Subject J. F. S.:

Frozen custard containing 508.9

w. uncooked starch, gm.. . . .

Fruit, gm.. . . . . . Sugar, gm.. . . . . . .


Feces, gm.. . . . . . . . . Amount utilized, gm. Digestibility of en-

tire ration, per cent Estimated digesti-

bility of uncooked starch alone, per cent.. . . . . . . . . . . . .

- Average food con-

sumed per subject per day, gm..

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C. F. Langworthy and Harry J. Deuel, Jr. 39

TABLE VI.

Summary of Digestion Experiments with Uncooked Wheat Starch in a Simple Mixed Diet.

Expe&?t Subject.

1073 P. c. 1075 H. I,. G. 1076 E. L. M. 1077 J. F. S.

Average . . . . . . . . . . . . . . .

.

Digestibility of entire ration.

Protein. / Fat. 1”~~~“-) Ash.

per cent per cent

90.6 96.6 94.2 92.8 91.6 91.8 93.1 94.3

--

92.4 93.9

~~ per cent per cent

98.2 81.3 97.9 62.6 97.3 60.7 99.5 90.6

98.2 ( 73.8

Estimated digestibility of

uncooked wheat starch

&Xl~.

per cent

99.8 98.6 98.4

100.0

99.2

Wheat Starch.

Four experiments were conducted to determine the digestibility of raw wheat starch. All four of the subjects had taken part in the tests with raw potato starch, and two in the earlier ones with raw corn-starch.

The essential data for the interpretation of the experiments are given in Tables V and VI.

The diet as a whole furnished an average of 22 gm. of protein, 68 gm. of fat, and 359 gm. of carbohydrate perman per day with an average fuel value of 2,138 calories. The average amount of raw starch eaten per man per day was 188 gm. The subjects remained in apparently normal health during the diet period. It will be noted that practically all the wheat starch was assimilated in each case. No starch could be detected in the feces by the iodine test. Moreover, the other c0nstituent.s were very well assimilated, the coefficients of digestibility being 92 per cent for protein and 94 per cent for fat.

SUMMARY.

1. Raw corn and wheat starches were found to be completely assimilated and no trace of them could be found in the feces.

2. Seven experiments on raw potato starch gave values for its digestibility varying from 62.3 to 95.2 per cent; the average was 78.2 per cent.


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3. The ingestion of the potato starch caused disagreeable phys- iological disturbances not noted in the other experiments with raw corn and wheat starches.

4. The digestibility of the other constituents of the diet was not affected to any great extent by the large amounts of raw starch ingested.


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C. F. Langworthy and Harry J. Deuel, Jr.POTATO, AND WHEAT STARCHES

DIGESTIBILITY OF RAW CORN,

1920, 42:27-40.J. Biol. Chem.

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