ACKNOWLEDGMENTS
The author is indebted to Professor Dennis E . Wiant of
the Department of Agricultural Engineering at Michigan State
University, under whose supervision the investigation was
undertaken and to whom the results are dedicated.
He also wishes to express his thanks to the following
staff members of the s a m e ‘institution:

Doctor Erwin John

B e n n e , Professor of Agricultural Chemistry, for his assis­
tance in the chemistry of this problem; Doctor William D .
Baten, Professor of Statistics, for his generous assistance
in laying out much of the experimental procedure; Doctor
Walter M, Carleton, Professor of Agricultural Engineering,
for the help he gave in the graduate program; Mr. James
Cawood, Shop Superintendent of the Department of Agricultural
Engineering, for the assistance in constructing equipment for
this problem; and to Doctor Arthur W. Farrall, Head of the
Department of Agricultural Engineering, and his staff as a
v/hole for making materials, equipment, and facilities avail­
able for this study.
He wishes to thank Doctor H. H. Schopmeyer and John W.
Elling of the International Milling Company for their part
in making the comprehensive milling and baking tests.

Myron George Cropsey
candidate for the degree of
Doctor of Philosophy
Final Examination, August 1956.
Dissertation:

The Effect of One-Million Volt Cathode Ray
Irradiation on the Respiration Rate, Milling
Tests, and Baking Properties of Wheat.

Outline ©f Studies:
Major:

Agricultural Engineering.

Minor:

Mathematics, Physics.

Biographical Items:
Born January 29, 1910, Oakland, California.
Undergraduate Studies, University of California, 1929-33.
Graduate Studies, North Dakota State College, 1939-41.
Michigan State University, 1954-56.
Experience
Union Diesel Engine Co. 1936-37, Jr. Engineer.
U,S.Department of Agriculture 1937-41, Jr.Ag.Engineer.
U.S. Army 1941-46, L t . - Lt.Col.
Oregon State College 1946-present, Assoc.Professor .
Member:

Sigma Xi, Tau Beta Pi, Sigma Pi Sigma,

American Society of Agricultural Engineers,
American Society for Engineering Education,
Registered Professional Engineer, State of Oregon.

THE EFFECT OF ONE-MILLION VOLT CATHODE RAY IRRADIATION
ON THE RESPIRATION RATE, MILLING TESTS,
AND BAKING PROPERTIES OF WHEAT

By
Myron George Cropsey

AN ABSTRACT
Submitted to the School of Graduate Studies of
Michigan State University of Agriculture and Applied Science
in partial fulfillment of the requirements
for the degree of
DOCTOR OF PHILOSOPHY
Department of Agricultural Engineering

Year 1956

Approved

ProQuest Number: 10008520

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Myron George Cropsey

Large quantities of wheat are lost each year at moisture
levels slightly above those safe for storage.

Often because

of damp weather farmers are not able to harvest wheat at the
moisture percentages required for safe storage .

Frequently

wheat changes in moisture within the elevator or storage bin
so that it is no longer safe in storage,

The purpose of the

author*s experiments was to determine whether cathode ray
irradiation would reduce the respiration of wheat that was
slightly damp (14.0 - 17.0 percent moisture wet basis) and
not impair the milling and baking qualities.
A review of the literature disclosed that spoilage of
wheat was due principally to mold growth under the right con­
ditions

of temperature, humidity, and aeration.

The optimum

conditions of mold growth were found to be about 86 degrees
Fahrenheit at about 20 milliliters of air per gram of dry
matter and at high humidities.
Three types of tests were conducted:
thermos bottle, and comprehensive.

respiration,

The respiration tests

were conducted at optimum conditions of temperature and
aeration for mold growth and at the humidity corresponding
to the equilibrium moisture content of the wheat.

These

were ten-day tests with the carbon dioxide produced on the
tenth day and the free fatty acid at the end of the tests
used as a measure of deterioration.

The thermos bottle

tests consisted of recording the temperatures within pint
thermos bottles when held at 86 degrees Fahrenheit for 20

Myron George Cropsey

days.

The free fatty acid determination at the end of the

test was also used as a criterion of deterioration.

The

comprehensive tests were carried out for conditions of
greatest mold growth and at the doses found most effective
in controlling the production of carbon dioxide in the res­
piration tests.

At the completion of the conditions for

maximum mold growth a series of milling and baking tests was
made according to standards of the American Association of
Cereal Chemists.
Five runs of the respiration tests were completed at vari­
ous levels of treatment. The 900,000 rep (see page 4 for defini­
tion of rep) treatment was found to be one of the most effec­
tive treatments in lowering the production of carbon dioxide,
whereas the 700,000 rep treatment seemed to cause the least
free fatty acid at the end of the tests .
The thermos bottle tests were not very effective as there
was a significant difference in temperature in only one c ase .
The free fatty acid determination was lowest at the 700,000
rep treatment.
The comprehensive tests were carried out at zero and
900,000 rep treatments.
at the 900,000 rep level.

There was a burned odor and taste
While this was not great, it would

be objectionable to the consumer.

The other milling and

baking tests showed only slight differences between no treat­
ment and 900,000 rep treatment.

Myron George Cropsey

Cathode ray doses from 500,000 to 900,000 rep reduced
the respiration rate of slightly damp wheat (15.0 - 16.0
percent), but the doses at 900,000 rep had a slightly
burned odor and taste for both the milling and the baking
tests .

TABLE OP CONTENTS
Page
INTRODUCTION

1

Purpose of the Experiments

2

Points Investigated

3

Definition of Terms

4

REVIEW OP LITERATURE

5

Respiration

9

Microflora

9

Microorganisms on g rain.

9

Temperature.

12

Moisture.

12

Oxygen.

13

Microf lora on stored grain.

13

Review of Conditions for a Respiration Run

13

Methods of measuring respiration .

14

Rate of a ir supply.

15

Temperature for respiration t e s t s .

17

Length of time for a respiration r u n .

18

Indexes of deterioration.

20

Biological Effects of Irradiation

21

Cathode Rays

25

EQUIPMENT

29

Description of the Electron Accelerator
The transformer.

29
29

Page
The t u b e .

30

The electrical controls.

30

Efficiency«

31

The Respiration Chamber

32

Respiration Chamber for the Comprehensive Samples

34

List of Other Equipment

36

EXPERIMENTAL METHODS
Respiration Tests

37
37

Methods of selecting sam p le s.

39

Conditioning grain to the proper moisture.

42

Irradiating wheat to the required dosage#

44

Excluding carbon dioxide from incoming a i r .

46

Maintaining the wheat samples in the resplration chamber at a constant moisture level.

47

Maintaining a constant air supply.

52

Determination of carbon dioxide content.

54

Method of obtaining a respiration sample.

56

Measuring the respiration of a sample of wheat . 58
Errors in determining the rate of respiration.

60

Thermos Bottle Tests

63

Comprehensive Tests

65

Respiration run for comprehensive tes ts.

65

Milling and baking tests.

67

ANALYSIS AND RESULTS
Analysis of Respiration Tests
Analysis of the first respiration r u n .

68
68
69

Page
Analysis

of the

second respiration r u n .

71

Analysis

of the

third respiration r u n .

73

Analysis

of the

fourth respiration r u n .

77

Analysis

of the

fifth respiration r u n .

79

Summary of the Respiration Tests

83

Analysis of the Thermos Bottle Tests

83

Analysis

of thermos bottle test - run o n e .

84

Analysis

of thermos bottle test - run t w o .

85

Analysis

of thermos bottle test - run th r e e .

87

Analysis

of thermos bottle test - run four,

90

Analysis

of thermos bottle test - run five .

92

Summary of Thermos Bottle Tests

94

Comprehensive Tests

95

Analysis of milling and baking tests .
Summary of milling and baking te sts .

98
101

SUMMARY

102

BIBLIOGRAPHY

105

LIST OP TABLES
Page
Table

I. Parasitic Fungi and Bacteria Pound
Internally In W h e a t .

11

Table

II. Parasitic Fungi and Bacteria Pound
Externally on W h e a t .

11

Table

I l l . Influence of Aeration Rate on Interseed
Carbon Dioxide Concentration, Respiratory
Rate, Respiration Quotient, Pinal Moisture
Content, Fat Acidity, and Germination of
Regent W h e a t .

17

Table

IV. Influence of Moisture Content and Time
on the Respiration Rate of Wheat at 30°C .

19

Table
Table

Table

V. Lethal Effects of X-rays on Aspergillus
Niger .
VI . Effect of High-Voltage Gathode Rays on
Internal Infection of Stoneville 2B
Cottonseed.
VII . Samples for a Respiration T e s t .

24
25

39

Table V I I I . Moisture Content of Hard Red Spring Wheat
in Equilibrium with Various Relative
Humidities.

48

IX. Relative Humidity of a Few Saturated Salt
Solutions Held at 3 0 ° C .

49

Table
Table
Table
Table

X. Samples for Comprehensive Tests.
XI. Results of the First Respiration Run.
XII. Analysis of Variance for COg Produced 10th
Day First Run.

Table XIII. Results of the Second Respiration Run.
Table
Table
Table

XIV. Analysis of Variance for COg Produced 10th
Day Second Run.
XV. Results of the Third Respiration Run.
XVIa.Analysis of Variance of COg Produced 10th
Day Third Run.

66
69
70
71
72
74
74

Page
Table

X V l b . Analysis of Variance of COg Produced 10th
Day Third Run High Moisture Only.

75

Table

XVIc . Analysis of Variance of COg Produced 10th
Day Third Run Low Moisture Only.

75

Table

XVII, Free Fatty Acid - End of Third Run.

Table
Table
Table
Table
Table

XVIII. Analysis of Variance of Free Fatty Acid
End of Third R u n .

76a
-

XIX. Results of Fourth Respiration Run.

77

XX. Analysis of Variance for CO2 Produced 10th
Day Fourth Run.
XXI. Free Fatty Acid - End of Fourth Run.
XXII. Analysis of Variance of Free Fatty Acid
End of Fourth R u n .

77

78 ■
79

-

79

Table

XXIII. Results of Fifth Respiration Run.

80

Table

XXIVa . Analysis of Variance for COg Produced 10th
Day Fifth Run.

80

Table

XXI Vb. Analysis of Variance for COg Produced 10th
Day Fifth Run High Moisture Only.

80a

Table

X X IV c. Analysis of Variance for COg Produced 10th
Day Fifth Run Low Moisture Only.

81

Table
Table

XXV. Free Fatty Acid - End of Fifth Run.
X X V I . Analysis of Variance of Free Fatty Acid
End of Fifth R u n .

81a
-

82

X X V I I . Thermos Bottle Temperatures Degrees
Fahrenheit - Run O n e .

84

Table XXVIII. Analysis of Variance Thermos Bottle
Temperatures - Run One.

84

Table

XXIX. Thermos Bottle Temperatures Degrees
Fahrenheit - Run Two.

86

Table

XXX, Analysis of Variance Thermos Bottle
Temperatures - Run Two.

86

Table

X X X I . Thermos Bottle Temperatures Degrees
Fahrenheit - Run Three.

88

Table

Page
Table

XXXII, Free Fatty Acid Teat for Thermos Bottle Run T h r e e .

89

Table XX XII I. Analysis of Variance Free Fatty Acid Run Three

89

Table

90

Table
Table

XXXIV. Thermos Bottle Temperatures Degrees
Fahrenheit - Run Four,
XXXV. Free Fatty Acid for Thermos Bottle Run F o u r ,
X X X V I .Analysis of Variance Free Fatty Acid Run F o u r .

91
91

Table

XXXVII. Thermos Bottle Temperatures Degrees
Fahrenheit - Run Five.

92

Table

XXXVEII.Free Fatty Acid for Thermos BottleRun Five .

93

Table
Table
Table

XXXIX, Analysis of Variance Free Fatty Acid Run Five .
XL,

Milling Data.

X L I .Baking Data.

TableX L I I . Test for Milligrams of Maltose at 14%
Moisture.
Table X L I I I . Analysis of Variance Mgs of Maltose at 14%
Moisture.
Table
XLIV. Free Fatty Acid for Comprehensive Tests.
Table
Table

XLV, Analysis of Variance Free Fatty Acid
Comprehensive Test.
X L V I .Mixing Time.

93
96
97
98
99
99
100
100

LIST OP FIGURES
Page
Figure

1

Influence of moisture content on the res­
piration rate of wheat.

8

Figure

2

Influence of moisture content on the res­
piration of normal wheat subject to mold
growth and the same wheat with thioures at
a concentration of 1% to inhibit mold growth
at 3 0 ° C .

9

Figure

3

Percentage change In acidity values and
germination of hard red spring wheat stored
at 15.35% moisture at Hays, Kansas.

20

Figure

4

The Bragg ionization curve.

26

Figure

5

Range of low-energy beta particles.

28

Figure

6

Schematic diagram of respiration chamber.

33

Figure

7

Apparatus for comprehensive tests.

36

Figure

8

A Boerner Divider which was used to make an
equal random division.

41

Figure

9

Graph showing the comparative activity of
naturally damp wheat and of wheat dampened
in the laboratory three days before they
were incubated.

43

Figure 10

Spraying wheat with distilled water to con­
dition it to the proper moisture level.

44

Figure 11

The wheat sample on the conveyor ready to
be irradiated.

45

Figure 12

Equilibrium humidities of hard red spring
wheat at various moisture levels .

51

Figure 13

Filling gallon bottle D of the respiration
chamber.

53

Figure 14

Method of obtaining a respiration sample.

57

Figure 15

Adding 30 milliliters of Ba(0H)g to the
sample.

59

Page
Figure 16

Apparatus of determining total errors
for rate of respiration.

63

Figure 17

Production of COg v s . treatment - Run O n e .

70

Figure 18

Production of COg vs.

72

Figure 19

Production of COg v s . treatment - Run Three

75

Figure 20

Production of COg vs.

treatment - Run Four.

78

Figure 21

Production of COg vs.

treatment - Run Five.

82

treatment - Run Two.

1

INTRODUCTION
Wheat one or two percent above the moisture content
level for safe storage causes heavy losses for the farmer
and the elevator operator.

The farmer without grain dry­

ing equipment must combine his wheat at a moisture content
which will insure safe storage, and must protect it from
the weather after it is binned.

The elevator operator is

plagued with migration of moisture within the bin caused by
changes in air temperature.

The migration of moisture may

cause spoilage by raising the moisture content of the grain
in parts of the bin.
Only recently have the processes of deterioration of
damp wheat been understood.

Formerly it was believed that

respiration of the stored grain was alone responsible for
heat production.

It was believed that when respiration was

sufficiently rapid, heat was produced, more rapidly than it
was dissipated.
It had been observed that the heating of damp grain
was usually accompanied by mold growth.

It is now known

that microorganisms are always present on the surface of
grains and within the seed coat and it is now generally agreed
that molds cause the sharp increase in respiration when the
moisture content of grain exceeds a certain value.
For sorrfe time it has been known that cathode ray irra­
diation can kill many forms of living organisms including

2

molds.

A logical question then arises.

Will cathode ray

irradiation prevent spoilage of high moisture content grain
by killing molds on the surface and within the seed coat?
Wheat placed in bins immediately after irradiation will be
difficult to reinfest.
Cathode ray irradiation is cheap because of the high
efficiency of conversion of electrical energy into cathode
ray energy.

Overall efficiencies as high as 15 percent are

possible for converting electrical energy into radiation
energy absorbed by matter.

At this rate if electrical

energy were selling for one cent a kilowatt hour, then a
500,000 rep treatment would cost 7.8 cents per ton of wheat.
Purpose of the Experiments
The purpose of the experiments carried out in this pro­
ject was to determine if cathode ray irradiation reduced
respiration to a low level in slightly damp wheat and to see
if the milling and baking qualities were impaired.
Points Investigated
Three types of tests were performed:

respiration,

thermos bottle, and comprehensive.
The points investigated of Irradiated wheat under fixed
storage conditions were the rate of respiration, the rate of
rise in temperature, the change in fat acidity, and the
changes in milling and baking qualities.

3

The rate of respirat5.cn was determined after ten days
while held at 87 degrees Fahrenheit and fixed rates of air
exchange.
The rise in temperature of wheat kept in thermos bot­
tles for twenty days was measured by thermocouples.
At the conclusion of each run rancidity determinations
were made of a sample of each t e s t .
Milling and baking tests were performed by the Inter­
national Milling Company according to Cereal Laboratory
Methods of the American Association of Cereal Chemists.
These tests were made for those dosages of irradiation that
showed the greatest promise of reducing respiration.

4

Definition of Terms
In this thesis the letters "rep", which will appear
many times, represent a word for roentgen equivalent physi­
cal.

There is some confusion as to its definition, hut it

is best taken as the absorption of 93 ergs of radiation en­
ergy per gram of body tissue.

This unit usually applies
27
to ionization radiation not covered by the roentgen.
The
roentgen shall be the quantity of X- or gamma-radiation such
that the associated corpuscular emmission per 0.001293 grams
of air produces, in air, ions carrying one electrostatic
27
unit of quantity of either sign.
The term cathode rays will appear often.

It is gener­

ally understood to be energetic electrons produced by a manmade machine .
Frequently the two terms ’’radiation” and ’’irradiation”
appear.

’’Radiation” in this thesis refers to an act or pro­

cess of diffusion or emission of radiant energy.

"Irradia­

tion” is the act or process of receiving Incident radiant
energy.
The term "percent moisture" or "moisture" as used in
this thesis refers to the ratio expressed in percent of the
weight of moisture to the total wet weight.

5

REVIEW OP LITERATURE
Respiration
Respiration processes occur in almost every living
cell, whether plant or animal, to carry on their metabolic
1 S3
functions. ,

Respiration carried on by the intake of at­

mospheric oxygen in the cell is known as aerobic respiration
and is the usual type referred to when respiration is spo­
ken of * On the other hand, anaerobic respiration occurs in
the absence of atmospheric oxygen and Is responsible for
fermentations carried out by microorganisms to produce car­
bon dioxide and other organic compounds.
Below is a chemical equation for the cumbustion of a
carbohydrate and a fat under aerobic conditions.'*'
D-glucose:

a carbohydrate.

g6h 12°6-+- 602 ----> 6C02 H - 6HqO — |— 677 calories
180 grams -f— 134.4 liters —> 1 3 4 . 4 liters-j-108 grams
Tripalmitin:

a fat.

<G 15H 31G 0 0 >3 G 3H54-724O2^ 51G0 2i-49H 20H- 7617 calories
806.8 grams—1-1624 liters->1142 liters-|-833 grams
The quantity of heat given off in combustion by other carbohydrates is similar.

33

In anaerobic respirations carbon dioxide also is given
off and a number of organic compounds are formed.

However,

6

the cells undergo internal oxidation and reduction.

Under

these conditions the energy released by a unit of substrate
is less than for aerobic respiration.
It should be stated that neither the oxygen consumed
nor the carbon dioxide produced should be considered as a
complete index of respiration if external and internal con­
ditions are not controlled.

However, if the temperature is

held constant and the oxygen supplied is constant, the amount
of carbon dioxide produced can be used as an index of compar­
ison of metabolic activity.
The total respiration of a grain can be accounted for
by the viability of grain, or microorganisms,

and of insects.

Insects are generally of a local nature and can be much bet­
ter controlled than the activities of the other two.

The

respiration of microorganisms and of the grain itself is in­
fluenced by such factors as temperature, moisture content,
supply of oxygen, prior history of the grain, etc.
In dry grain that is insect free, the respiratory rate
is very low.*^

As the moisture content increases, the respi-

ratory rate increases.

5

At some critical moisture content

the respiratory rate accelerates rapidly until the grain b e ­
gins to heat.
en

This can be illustrated best by Figure 1.

from Bailey and Uujar.

5

tak-

When the heat produced by respi­

ration exceeds the rate at which the heat can be dissipated,
the grain

increases in temperature.

Recently, most investigations have shown that the sharp

7

increase in respiration is due to the growth of m o l d s .

A

relative humidity o f . about 75 percent is a minimum for the
growth of molds at room temperatures.

According to the work

of Coleman and F e l l o w s h a r d red spring wheat of 14.7 per­
cent moisture (wet basis) would be in equilibrium with an
atmospheric relative humidity of 75 percent.

This is just

at the moisture level in wheat where there is a sharp in­
crease in respiration.
Respiration bests in which grain has been continuously
aerated support the theory that the acceleration of respira­
tion above

a certain moisture level Is due to mold growth.

Milner, Christensen, and Geddes have made the following ob­
servation concerning mold growth:
That molds are the primary cause of heating and
deterioration of various kinds of stored seeds at
moisture contents where molds can grow has been shown
by a member of workers, including Gilman and Barrow
(1930) J-9, Milner and Osddes (1946, 1946a)35,36, Nagel,
and Semeniuk (1947)37,
in a comprehensive review of
the literature on the deterioration of corn in stor­
age, Semeniuk and Gilman (1 9 4 4 ) ^ 2 state that M . . .
the conditions under which deterioration occurs and
the changes which follow its initiation, indicate that
it is primarily a biological decomposition. . .
To continue:
Sound wheat stored at 30 degree centigrade and at
moisture contents above 16.1 percent was rapidly over­
grown by molds. The increase in respiration and de­
crease in viability of the seed with increasing mois­
ture content was proportional to the increase in .
molds

8

Carbon dioxide
respired per 24hrs q
per 100 grams
of dry matter
5

18
16
14
12
10
Percent moisture of wheat (wet basis)
Pig. 1 Influence of moisture content on the
respiration of wheat

In view of these results the author has concluded that
mold growth is responsible for the initial spoilage and
deterioration of wheat at moisture contents where mold will
grow .

9

140
mg of
002
120
oer 100 gm
of dry matter - _
100
per 24 hours
*

30
norma
60
0 mold
growth
Inhibited

40
20

12

14
16
18 20
22
Percent Moisture (Wet B a s i s )

24

Pig, 2
Influence of moisture content on the
respiration of normal wheat subject to mold
growth and the same wheat with thiourea at a
concentration of 1% to inhibit mold growth at
30 C. The respiration trials were conducted
?or 3*3. daJ 3 an'3- the rates clotted for the 10th
day ,
Microflora
Microorganisms on gr ain .
fungi and bacteria,
grains.^

^

9^

There are a wide variety of

including actinomycetes, on cereal
Their activity results in spontaneous

heating, the development of off-odors, tastes and various
discoloration of the grains, although the exact nature of
their activity is not always known.^
Bacteria, fungi,
organisms.

and actinomycetes are simple micro­

Fungi are classified as molds, yeasts, and

yeast-like fungi.

Most microorganisms found in grains

10

require organic materials for growth.

Their diversity of

type makes growth of one or another of them possible over
a wide range of environmental conditions.
Microorganisms are found on both the inside and the
outside of cereal grains.
comment,

Semeniuk makes the following

"It is known that the parasitic fungi and bacteria

listed in Table I may be carried internally.

Their pres­

ence in kernels depends on their own parasitic aggressive­
ness, on the action of true parasites, on the stage of
grain development when they are present in the air.
on grain suseptibility
However, Thompson

. . . , and on weather

48

. . ,

...

.“-J-

states that heating cf damp wheat

is due to a sub-epidermal fungi entering through the stem
and that most of the heat of respiration is due to these
internal fungi.
On the surface saprophytes are the main components
while parasites may also be present.
Stark

P4

James, Wilson, and

found on the surface of wheat those listed in

Table II.

11

Table I.
PARASITIC FUNGI and BACTERIA FOUND INTERNALLY IN WHEAT*

Fungi
Calonectria graminicola
Fusarium s p p .
G . zeae
H . sativum
5 . nodorum
5 , tritici
Bacteria
Xanthomonas Translucens

* Adapted from Dickson

and Greaney and Machacek

21

Table II .
PARASITIC FUNGI and BACTERIA FOUND EXTERNALLY ON WHEAT*

Acrostalagmus cinnabarinus
Alternaria tenuis
Aspergillus glaucus
Aspergillus candidus
A . f lavus "*
A . fumigatus
A . n iger
A . oryzae
A . vers 1eolor
CepHaTosporium spp.
C. curtipes
Cephalothecium roseum
Fusarium culmorum~
F . poae
F. scirpi var.acuminatum
FT semitectum v a r . major
Helmlnthosporium sativum

Hormodendrum pallidum
H . viride
Mucor cireinelloides
M . racemosus
Paecilomyces variot1
Penioillium chrysogenum
P . flavi-dorsun
P . frequentans
P . purpurogenum
FT rugulosum
P . s'plnulosum
P . terrestre
Rhizopus spp.
Scopulariopsis spp.
5. brevicaule
Septoria nodorum
Trichoderma lignorum

* From James, Wilson and S t a r k ^

12

The principal factors determining the activity of m i c r o ­
organisms in stored grains are temperature, moisture, and
oxygen supply according to Semeniuk in Anderson and Aleock.^
Temperatures .

Microorganisms have a maximum, a minimum,

and an optimum temperature at which they grow.

At tempera­

tures outside the range of growth microorganisms die.

They

die quickly at temperatures above the limit for growth and
slowly at temperatures below the limit for growth.

Those

at high moisture content die more rapidly than those at low
moisture content when outside their range of growth.'*'
Microorganisms produce heat as a result of their metab­
olism

f the amount of heat they produce depending upon such

factors as temperature, moisture, oxygen concentration, n u ­
trients, and the age of the cells.
Moisture.

Water is required in the metabolism of micro­

organisms and is a part of their physical structure.

Semen­

iuk classifies microorganisms according to their water re­
quirements :
Microorganisms are classified as hydrophytes, mesophytes, or xerophytes on the basis of their minimum
moisture requirements for growth . . .
. Hydrophytes
grow when their minimum requirements are greater than
90% relative humidity, mesophytes when the minimum re­
quirement is between 80 and 90$, and xerophytes when
the minimum requirement is les3 than. 80$. Hydrophytes
grow best at 98 to 100$ relative humidity, and xero­
phytes grow best at 95 to 100$ relative humidity, or
at some lower value . . .
Bacteria are hydrophytes,

so far as is known.

Therefore,

bacteria grow faster on a solid or semisolid substrate in a

13

moist atmosphere than in a dry atmosphere.
Molds can be hydrophytes, mesophytes, or xerophytes.^
For this reason molds can be expected to be active at a much
lower relative humidity than bacteria.
Oxygen.

Microorganisms are subdivided, according to

their oxygen requirements, into anaerobes and aerobes.
teria are in both these classes.

B ac­

Molds also grow at wide

ranges of oxygen requirements.
Microflora in stored gr ain.

As was pointed out before,

molds grow at lower relative humidities than bacteria.

It

is usually the molds that cause heating and spoiling of grain
in storage.

Molds die slowly in stored grain when held below

the minimum relative humidity for growth.
According to Semeniuk in Anderson and Alcoek^- molds grow
faster and sporulate more abundantly as the relative humidity
approaches 95 to 100 percent, the temperature approaches 28
to 32 degrees centigrade, and the oxygen concentration exceeds
a level of about one percent.
Review* of Conditions for a Respiration Run
To test the effectiveness of the cathode ray treatment
in improving the storage quality of wheat, one must select
conditions giving a critical difference that would be simple
and direct to measure and capable of being measured over
a reasonable length of time.

Inasmuch as mold growth is the

principal cause of the deterioration of wheat, it was

14

decided to select conditions for its maximum growth.

Tem­

perature and rate of aeration were selected on the "basis of
research done by others in determining maximum mold growth.
The length of time to run a trial was chosen for a period
that would be sufficient to give a definite indication of
deterioration of the wheat.

Finally,

indexes of the condi­

tion of the wheat and degree of deterioration also had to be
chosen.
Methods of measuring respiration.

There are three gener­

al methods for measuring the respiration of dormant seeds.
In one method the seeds are kept in a closed container for a
sufficient length of time so that the carbon dioxide content
will build up to a measurable amount.
analyzed for carbon dioxide.
tem.

The air inside is then

This is called the close d sys­

In the second method seeds are subject to a continuous

aeration and the air passing through the seeds is analyzed
for carbon dioxide.

Finally, mi.crotechnlcs are employed to

measure respiration of Individual seeds.
5
Most workers in cereal grains, namely Bailey and Gujar ,
Goleman, Rothgeb and Fellows1 2 , Lamour, Clayton and Wren28
40
shall
, and Ramstead and Geddes
, have used the closed sys­
tem.

Matz and Milner3^, and Milner, Christensen and Geddes34

used the continuous aerated system.
Microtechnics were used by Stiles and William.

44

In

this method the respiration of individual seeds was measured

15

"by determining the electrical conductivity of a wire which is
in the atmosphere of the seed "being measured.

The tempera­

ture of a metal wire changes depending upon the type of gases
surrounding the wire, because gases present determine the
rate at which heat is dissipated.

In this manner the presence

of carbon dioxide can be detected once the instrument is cal­
ibrated .
The Warburg-Barcroft manometeric apparatus also has been
used in respiration studies with wheat.
Finally, there have been techniques developed for the
measuring of respiration in grain bins.
Rate of air supply.

The rate at which wheat and the

microorganisms both within and on the surface of wheat respire is dependent upon the supply of oxygen,

1 5 34
9 9 ~ However,

it was not until recent times that respiration under fixed
conditions of temperature, moisture content, and air exchange
was used to determine the deterioration of cereals.
Perhaps the most careful work of determining the influ­
ence of various rates of aeration on wheat was that done by
34
Milner, Christensen, and Geddes in 1947,
In this experi­
ment studies were made of the respiration in relation to
moisture content, mold growth, chemical deterioration, ger­
mination, and rate of aeration.
in Table III.

The results are summarized

In rates above 12.5 milliliters per gram of

dry matter per day, the increase in respiration is not great.

16

Matz and Milner ( 1 9 5 1 ) , ^ in order to determine the influence of chemicals on respiration,

selected 20.0 milliliters

of air per day per gram of dry matter as part of a standard
test to determine rates of respiration.
For the work in this thesis an attempt was made to aer­
ate the samples at about 20.0 milliliters per gram of dry
matter.

As a matter of record, the samples averaged between

16.0 - 20.0 milliljters per gram of dry matter per day.
This variation in air exchange should make little difference
in the results, as can be seen from Table III.

17

Table III*
INFLUENCE OP AERATION RATE ON INTERSEED CARBON DIOXIDE
CONCENTRATION, RESPIRATORY RATE, RESPIRATION
QUOTIENT, FINAL MOISTURE CONTENT, FAT
ACIDITY, AND GERMINATION OF
REGENT WHEAT
(From Milner, Christensen,and Geddes 1947)
________________
p. 190_________________________
AeratIon
Respiratory Rate
Interseed CO q Concentration
Rate
3rd day 5th day 9th day
3rd day 5th day 9th day
ml/gdm/day
mg.COgper lOOgdm per "
%
" X ' ~ ..........
%
Original
------------Sample
12.41
6.4
10.1
13.0
0.16*(HP ) 5 .60
8.99
7.28
3.2
^
101.1
15.47
18.69
40.3
85.3
6.4
126.2
178.2
4.78
16.14
52 .8
11.47
65.2
12.5
3.02
12.44
6.67
143.3
269.3
2.02
18.9
8.86
4.39
65.6
289.7
142 .7
25.1
1.64
3.49
7.32
70.5
150.2
316.5
Aeration

Respiration Quotient

Moisture Fat
IniR a t e ___ 3rd day 5th day 9th d tialFlnal Acidity
ml/gdm/day
* %
%
mg KOH
____________1 0 0

Original
Sample
0.16*(N? )
3.2
6.4
12.5
18.9
25.1

---

---

6 .15
0.95
1.01
1.04
1.03
1.07

9.77
0.95
0.95
0. 93
0.92
0.92

---

13.20
0. 90
0.83
0.80
0.80
0.82

12.4
20.4
20.4
20.4
20.4
20.4
20.4

12.4
20.5
20.5
20.8
20.9
21.0
21.1

Germination
%

g______________

12.6
12.7
65.9
69.6
69.6
71.6
74.4

98
95
24
18
18
19
16

(All tests run at 30°Centigrade,)
J
«- Volume of air (20.93% oxygen)
equivalent to nitrogen con­
taining 1.01 oxygen.
Temperature for the respiration tests .

That molds are

the principal cause of the deterioration of stored grains
can be inferred from the discussion under microflora.
these tests it was decided to select a temperature that

In

18

would be maximum for the growth of molds.

According to Sem­

eniuk in Anderson and Alcock^, molds grow fastest in the tem­
perature range 28 to 32 degrees centigrade when the watervapor pressure approaches 95 to 100 percent and the oxygen
concentration exceeds a level of about one percent.

A tem­

perature of 30 degrees centigrade was therefore selected as
a suitable temperature to test the respiration of wheat.
Milner, Christensen, and Geddes3 4 , Matz and Milner3 2 ,
o
and Bottomley, Christensen, and Geddes used a temperature
of 30 degrees centigrade to test the effect of mold growth
on stored grains.
Length of time for a respiration r u n .

After a tempera­

ture, humidity, and aeration rate were selected for maximum
mold growth, it was necessary to choose a practical length
of time to run the experiment so as to have comparable resuits,

Milner, Christensen, and Geddes

34

have made a com­

plete analysis of the rate of respiration of wheat at a num­
ber of moisture percentages from one to twenty days at 30
degrees centigrade.

This is summarized in Table IV.

It can

be seen that at the ten-day level all samples up to 16.8 per­
cent moisture

(wet b a s i s ) show a definite trend in their

respiration rates.

Ten days for a respiration run at 30 de­

grees centigrade was selected by Milner, Ghristensen,

gA

Geddes (1947)'

gp

and Matz and Milner (1951)

and

19

A length of ten days is a practical limit that was long enough to show results, hut not so long as to interfere with
the number of runs possible with a limited time.
Table IV.
INFLUENCE OF MOISTURE CONTENT AND TIME
ON THE RESPIRATION RATE OF WHEAT
AT 30° CENTIGRADE
RESPIRATION RATE,
MG.C02 PER 100 G. DRY MATTER PER 24 HOURS
(Extracted from Milner, Christensen,and Geddes

34

)

Day

12.3

13.6

Moisture Content % (Wet Basis)
13.8 14.5 ■”R " T 16.3 16.8

1
2
3
4

0.05
0.04
0.06
0.07

0.13
0.15
0.15

0.13
0.18
0.25

---

---

5
6
7
8

0.08
0.08
0.08
0.09

0.14
0.15
0.12
0.15

9
10
11
12

0.08
0.09
0.10
0.04

13
14
15
16
17
18
19
20

0.16
0.25
0.31

0.20
0.37
0.45

0.54
0.86
1.03

0.25
0.25
0.26
0.24

0.36
0.36
0.35
0.36

0.48
0.51
0.49
0.41

1.24
1,38
1.72
2.26

1.8
1.8
2.7
4.0

0.12
0.14
0.14
0.12

0.26
0.23
0.25
0.23

0.36
0.36
0.33
0.33

0.53 5.58
0.55 6.98
--0.60
0.65 15.88

5.9
9.1
12 .4
15.2

0.07
0.08
0.07
0.08

0.10
0.14
0.14
0.13

0.22
0.23
0.24
0.22

0.33
0.34
0.36
0.41

0.78
0.90
1.06
1.25

17.71
19.21
20.04
20.54

17.7
18.9
19.8
20.2

0.07
0.07
0.10
0.07

0.13
0.11
0.14
0.11

0.22
0.23
0.24
0.23

0.42
0.46
0.53
0.57

1.48
1.75
2.08
2 .53

21.06
21.47
22.67
23.35

20.3

1.8
1.4
1.5

-------

20

Indexes of deterloration.

It has long been known that

grain and mill products increase in acidity while in stor­
age.

As a result a series of tests have been developed to

determine the quality of wheat in storage by measuring the
titrable acidity of grain.
(1)
(2 )
(3)
(4)
(5)

Foremost of these are:

The Besley and Baston Method.
The Greek or Balland Method.
Schalerud's Method.
The Former A.O.A.C. Tentative Method.
Methods Based on Determination of Free Fatty
Ac i d s .

None of these methods yielded correlated results .
50
Zeleny and Coleman
made a critical study of this problem.
Under conditions in which wheat was deteriorating in storage,
a series of acid tests was made on samples collected at
periodic intervals.

The results of these tests are shown

in Figure 3 below.

160

Fat A c idity

120
Percentage
Increase orso
Decrease
40

Phosphate acidity
4
*

0
-40

.... -n H .111
Total acidity

— *— X—

\

\

X -- X ->. - x- x

x

Amino-ac id
acidity

-SO
Germination
-120
o

10
20
30
40
50
60 .
Days in storage
Fig.3 Percentage change in acidity values and germination
of hard red winter wheat stored ,a± 15,35;t moisture at
Hays, Kansas (Zeleny and Coleman)t

21

They concluded from these te,3ts that a method based on
determination of free fatty acids was the best test of the
group to determine the deterioration of grain in storage .
For this reason the determination of fat acidity was used
as an index of deterioration in a series of experiments for
this thesis.
Under the section, Respiration,

it was shown that car­

bon dioxide is an index of the metabolic activity of living
cells.

While the complete combustion of a carbohydrate is

not the same for every carbohydrate, their differences are
not great .

The complete combustion of a grain is determined

the grain itself, microorganisms, and insects.

Insect

activity can be controlled, and therefore the total metabo­
lic activity of the grain itself and of microorganisms can
be fairly well determined by the carbon dioxide respired.
The rate of carbon dioxide given off is thus a critical
index of the rate at which a grain is deteriorating.
Biological Effects of Irradiation
An atom consists of a charged heavy nucleus surrounded
by electrons traveling in discrete orbits.
come ionized by losing an electron,
shell.

An atom may b e ­

usually in the outer

Ionization can be caused by another electron strik­

ing the electron of the atom In the case of cathode rays, or
by electromagnetic waves in the case of X-rays.

In some in­

stances, an electron may not be knocked entirely out of the
shell, but only to another orbit of lower

energy.

In this

22

cireumstance we say the atom is excited.

27

The ionization

and excitation account for most of the dissipation of energy
from irradiation except at very high energies of ra d i a t i o n . ^
The exact process whereby biological changes due to ir­
radiation take place is not fully kn o w n ,

It is theorized

that some biological effects may take place owing to the loss
of an electron, but of greater importance is the fact .hat
the ionized atom can take part in a chemical change.

Chemi­

cal combinations are set up which in turn can cause dissocia­
tion of the molecules.

This, of course, can lead to drastic

changes in the original material, since most organic materials
consist of large molecular structures built of many atoms.
The dose required to produce chemical change by direct action
is inversely proportional to the molecular weight.

31

Another

theory frequently advanced is that since the energy loss or
gain is confined to a very small portion of the atom, this
point could be at a very high temperature.
of the ,!point-heatM theory.

This Is the basis

31

A number of investigators have been Interested in the
effects of cathode and X-ray irradiation on cereals and mi croflora and insects found on cereals.

The effect of cath­

ode rays on germination and early growth of wheat was studied
46
by Soderholm and Walker.
They found that dosages between
10,000 - 200,000 rep did not limit germination, but the high
dosages had pronounced effect on further growth.

They also

found that dosages between 10,000 - 30,000 rep temporarily

23

limited the vigor of wheat.

Dosages between 40,000 -

200,000 rep not only limited vigor, but completely checked
continued growth.
Baker, Taboada, and Wiant^
ode rays on cereal insects.

studied the effect of cath­

They found that 10,000 rep

would sterilize flour beetle and granary weevil eggs and
that this same dose would prevent the adults from reprodu­
ce
cing. A dose of 5 x 10 rep was lethal to 100 percent of
adult flour beetles immediately after treatment, whereas a
dose of 2.5 x 10

rep was lethal to 100 percent of adult

granary weevils immediately after treatment.
Smith
cereals.

studied the influence of X-rays and heat on
He noted the effect of chromosomal aberrations,

percent of germination, and the height of seedlings after
treatment with X-rays and heat.

He found that severe heat

delayed or prevented germination, but that if the seeds ger­
minated, they grew more vigorously.

X-rays did not delay

or reduce germination so much, but after the more severe
treatments all the seedlings did not germinate at o n c e ,
Dunn, Campbell, Fram, and Hutchinslb made a series of
experiments on the biological effects of irradiations.

Some

of the conclusions they reached are as follows:
1* Dosages required to destroy bacteria 'with cathode
rays appear to be similar to those necessary with
X-rays .
2, It took extremely high dosages to destroy enzymes.
In many cases doses of 8,000,000 roentgens and
higher were required.

3. For vitamins 500,000 roentgens resulted in high
losses in the reduced ascorbic acid.
4. Non-spore forming bacteria were destroyed by dosage
of less than 500,000 roentgens and from 64.5 to 99.
percent of them were destroyed by 35,000 roentgens .
Most spore forming bacteria were destroyed by appli
cation of less than 1 ,000,000 roentgens and 15 - 96
percent were destroyed by 25,000 roentgens.
5 . The effect of X-rays on molds is summarized by the
table below.
Table V.
LETHAL EFFECTS OF X-RAYS ON ASPERGILLUS NIGER16

Dose in
roentgens
25.000
50.000
100,000
250.000
500.000

Average
percentage
destruction
of molds
95 .96
99.63
99.98
99 .999
100.00

Range of percentage
destruction of molds
91.29 to
98.93
99.999
99.999
100.00

98.25
99.96
99.999
100.00
100.00

In the case of the genus Mucor a dose of 1,000,000
roentgens destroyed all of the individual molds, whereas
500,000 roentgens destroyed 99 percent of them,
Lambou, et al/

used cathode rays produced by a Van de

Graaff generator at three million volts on cottonseed to
determine the effect on molds, bacteria, and germination.
These are summarized in the table that follows.

25

Table VI.
EFFECT OF HIGH-VOLTAGE CATHODE RAYS...
ON INTERNAL INFECTION OF STONEVILLE 2B COTTONSEED
______________ Seeds infected with"________ __
Dose of
Molds and
Total
cathode
Molds
Bacteria
bacteria
infected
%_______________ %
%
rays (rep)_______ %___
None
500,000
1 ,000,000
1,500,000
2 ,000,000
2,500,000
3,000,000

58
92
36
0
0
4t
4t

0
4
0
0
0
0
0

36
4
4
0
0
0
0

94
100
40
0
0
41
4t

* - Samples of 50 seeds each were used for the analyses.
t - Probably a plat© contaminant--molds were not of the same
genera as appeared on the other plates.
Lambou

P6

also found that high-voltage cathode rays re­

duced the number of microorganisms on and in the seed.

It

was done without bringing about any changes in the moisture
and free fatty acid content, but there was a reduction in
germination and an inhibition of growth.
Cathode Rays
Cathode rays, accelerated electrons, and beta rays all
refer to high-energy electrons.

Usually cathode rays and

accelerated electrons refer to machine accelerated electrons,
while beta rays refer to electrons emitted by radioactive
decay.
Electrons are relatively light, small particles

26

containing a fixed charge.

27

In passing through matter an

electron might give up a large part of its energy in a single
inelastic collision with an atomic electron, or it may pass
nearly through the material "before colliding inelastically
with an electron.

An electron is light*

It can rebound in

many directions when it hits a heavy particle or another
electron; as a result, there Is a great difference of range
of electrons of the same energy.
Electrons also lose energy by radiative collision.
When an electron is accelerated or deaccelerated in the elec­
tric field of the nucleus, X-rays are produced.

This pheno­

menon is known as Mbremsstrahlung11, a German word meaning
27
’'braking radiation.”
The specific ionization (total number of Ions formed
per centimeter of path corrected to one atmosphere) for the
mean electron at various energies can be seen in Figure 4.

Specific. 200
Ioniza
tion

10^
10 °
10 ' 10 °
Energy (Electron volts)
Fig.4

The Bragg ionization curve

27

27

The shape of this carve can he explained as follows.

At low

energies or speeds an electron can interact with other elec­
trons of an atom and therefore can transfer some of its en­
ergy to them easily.

In some instances enough energy may he

transferred to other electrons to produce delta rays.

Delta

rays are electron ejected from the shell of an atom hy inter­
action with electrons coming from outside the atom.
In the case of faster electrons the speed is great enough so that the field of the electron does not have time to
interact with the field of other electrons.

This is true at

ahout one million volts, as shown in Figure 4.
As the energy or speed of the electron increases heyond
one million electron volts, relativistic considerations must
he taken into account.

Thus the electric field of the elec­

tron is condensed in a plane normal to its path.

This in­

creases its strength in this space, and consequently the
electron reaches out further to interact with more electrons.
The range energy relationships for electrons of one mil­
lion electron volts and helow can he seen on Figure 5.
PO
curve was obtained empirically hy Grlendenin.

This

28

l.Of
Energy

7T.T

IT

.
i!

* 4 -.....

_- y

/
-

■i
1.

--

(Mev)
0.1

L....
h- I

“ t

.01 L
0.1

--- ^

1.0
>10
jl.w
oJ
-u
100
500
Range (mg/cm^ of Al)
Pig.5
Range of low-energy beta particle:
20
Prom Glendenin,Hueleonies
2,1 (1948)

29

EQUIPMENT
Description of the Resonant Transformer Electron Accelerator
The essential features of the accelerator are the tube,
the transformer, the tank, and the motor-generator set.
These are all combined into two large units with appropriate
controls and protection.

The transformer is enclosed in a

tank made of three-eighths Inch steel.

Within are the pri­

mary windings and the secondary windings.
the transformer is the tube.

At the center of

The output is a sine-wave en­

ergy curve delivered during the rectifying half-eycle.

It

delivers 1 ,000,000 volts at the peak.
The transformer.

The primary windings are excited by

the motor-generator set.

Three-phase, 60-cycle, 220-volt

current is converted to 180-cycle, single-phase current.
The number of secondary turns is so chosen as to make its
natural period of oscillation match that of the supply cir­
cuit .

This transformer has no metal core, and the magnetic

flux does not interfere with the operation of the tube .

The

advantage of this system is reduction in weight, no hystere­
sis losses, and small space requirements.

The secondary coil

is placed just within the primary windings.

To protect the

secondary coil from the high voltage, sulfur hexafluoride
gas under pressure of 60

pounds per square Inch in the steel

tank is used to increase the dielectric strength between the

30

turns of the secondary.

Also the potential is graded from

one end of the coil to the other so as to prevent creepage
over the solid dielectric "between coils .

The secondary

windings are connected at intervals to the 12 sections of
the t u b e .
Narrow strips of silicon steel electrically separated
from one another are placed on the outside of the primary
windings to shield the steel tank from the magnetic field
of the transformer.
The tube .

The tube consists of 12 sections of pyrex

glass tubing sealed to fernico rings which carry the accel­
erating

electrodes.

These electrodes or plates inside the

tube are of stainless steel and provide acceleration to the
electrons .

At the top of the tube is the cathode, which con­

sists of 6.5 convolutions of 8.5 millimeters tungsten wire
mounted in an electrostatic cup.

The whole tube is evacu­

ated to about 28 inches of mercury.

A focusing coil near

the bottom of the tube determines the spread of the beam
below.

Electrons shoot out through a stainless steel window

at the bottom of the t u b e .
The electrical controls.

There are two principal con­

trols, tube voltage and filament current.

The generator

field controls the voltage in the primary of the transformer,
and the primary voltage controls the voltage in the secondary
coil.

The secondary coil determines the tube voltage.

31

Beneath the steel tank a reversible motor rotates a glass
tube which controls the filament current.

The glass tube

extends up through the tank to a variable inductance in the
filament circuit .

Change in the inductance controls the fi­

lament current.
Power for the transformer is obtained from a synchro­
nous motor-generator set.

Three-phase, 60-cycle, 230-volt

power is converted into 180-cycle,

single-phase power.

There

are the usual motor controls and safeties.
A blast of air beneath the window of the tube cools the
window.

Whenever the electron beam is passing through the

window, this blast operates.
Beneath the accelerator is a conveyor belt that can run
at a number of‘precise speeds.

This is not a part of the

accelerator, but is one of the controls to determine dose
rate of the material being irradiated.
Efficiency.
mated as follows:

The efficiency of the machine can be esti­
at 1 ,000,000 volt peak and nine milliam-

peres in the tube there will be a beam-out current of six
milliamperes.

Fourteen kilowatts of input power will be

required at this setting.

There will be (,707)(,006)

(1 ,0 0 0 ,0 0 0 ) or about four kilowatts of beam-out power which
will make an efficiency roughly of about 30 percent.

If the

beam is used to 50 percent capacity on the material being
irradiated, 15 percent of the energy will be applied to use­
ful work.

32

The Respiration Chamber
The continuous aerated method was selected to measure
respiration in this study because it represents a set of
conditions that would be apt to occur in grain during storage.
The microtechnic method was not selected since individual
seeds tend to vary too greatly from the average.

The inter­

rupted method-, in which carbon dioxide is allowed to accumu­
late between the seeds, was rejected because respiration is
suppressed when carbon dioxide accumulates and therefore
tends to inhibit maximum respiration.
The respiration chamber consisted of the box, the train
of Brlenmeyer flasks, the heating system, and the timer, the
purpose of the chamber being to maintain wheat at a constant
temperature and to supply a constant source of air at a given
relative humidity free of carbon dioxide.
The box was constructed of one-quarter inch plywood cov­
ered with one-half inch celotex insulation and reinforced with
one-by-two-inch wood at the edges.

It was 24 inches high,

30 inches wide and 42 inches long.

A shelf approximately 30

by 30 inches divided the box horizontally through the middle.
This permitted a 6 by 30 inch space on each end of the shelf
which provided a path for the air to circulate inside the box.
Heat was provided by one 100-watt electric light bulb.

A

thermostat Inside controlled the light bulb.
The box was tested for variation In temperature.

A hygro-

thermograph placed inside the box showed a variation of plus

33

or minus one degree at 86 degree Fahrenheit, with a cyclic
period averaging 24 minute s.
ibrated

This hygrothermograph was cal­

with a mercury thermometer calibrated in turn with

a certified thermometer.
In the respiration method adopted, air was passed over
a thin layer of wheat in a gallon bottle and analyzed at in­
tervals for carbon dioxide.

Air was sucked through the sys­

tem by the continuous drop in level of a saturated solution
of calcium chloride in a gallon bottle (see Figure 6 ).

The

solution level was lowered by a synchronous motor of a time
clock F.

A rubber tube ’b ’ connected from the gallon bottle

D determined the .height of liquid level in this gallon bottle.

j time clock

30 G Box
1st gallon
bottle GaGlg t

150 ml
B a ( O H )o
Fan

150 ml
either KG1
or Na Cl

1000 ml
\
approximately
150 gm of
wheat
2nd bottle
to collect CaClg

F i g # 6 Schematic diagrsm of respiration chamber

34

As the time clock lowered the rubber tube, the liquid level
in both the gallon bottle and the tube dropped.

The general

scheme can be seen in Figure 6 .
The liquid that ran out of bottle D was collected in
bottle S.

If the air inside the system was at atmospheric

pressure, then the amount of air passing through the system
could be determined by the amount of liquid collected in the
second bottle S.

Actually there was only a slight difference

between the inside pressure and atmospheric pressure as meas­
ured by a water manometer.

Usually the variation of pressure

between inside and outside was one-eighth to one-quarter inch
of w a t e r .
Respiration Chamber for the Comprehensive Samples
A grain sample for comprehensive testing had to be at
least twelve hundred grams in size owing to the number of
tests and quantity of grain required per test .

This larger

sample necessitated a change in apparatus from that used for
the respiration determinations.

It was desired that condi­

tions for maximum rate of mold growth be duplicated, which
were 36 degrees Fahrenheit and 20 milliliters of air per
gram of dry matter in 24 h o u r s .

A large room was used to

maintain a temperature of 87 degrees Fahrenheit by electric
heat and a suitable thermostat.

Eighty-seven degrees Fahren­

heit was one degree higher than was desired, but was diffi­
cult to change.
The air exchange system depended on the displacement

35

of one gallon of water on an average of every four hours and
48 minutes.

The average air exchange was about 16.0 milli­

liters of air per gram of dry matter per 24 hours which Is a
lit bis lower than the 19.0 milliliters averaged in the res­
piration tests.

Even so there should be insignificant dif­

ferences in respiration according to Table III.
The apparatus used for making the 10-day conditions for
ideal mold growth consisted of three one-gallon bottles and
two 150-milliliter Erhlenmeyer flasks connected in a train
by rubber tubing.

The gallon bottle A (Figure 7) contained

a screen cylinder 3 3/4 inches in diameter and approximately
10 inches in height.

W h e a t was placed between thi3 cylinder

and the walls of the glass bottle, forming a thickness of
wheat approximately one Inch through.
A gallon of air was exchanged in the following manner.
Gallon bottle 3 was filled with water.
was opened, water ran down to bottle G.

When pinch cock d
This in turn drew

air through the train of Erlenmeyer flasks and the wheat sam­
ple to replace the water which had run out (see Figure 7).
Every four hours and 48 minutes this process was repeated by
exchanging bottles B and G, and exchanging the tube connec­
tions, the procedure being continued for 10 days.
this method did not provide continuous aeration,

Although
it was a

close approximation to such conditions,
Erlenmeyer flasks E and F were used for the same purpose
as those in the respiration bests.

Flask E contained an

36

excess of barium hydroxide to remove any excess carbon diox­
ide in the atmosphere.

Flask F was used to keep the air pas­

sing through the wheat sample at the desired relative humid­
ity by use of suitable salt solutions.

Fig*7 Apparatus for comprehensive tests

List of Other Equipment
Other equipment used is listed below.
Hygro-Thermograph (10° - 100°F) (0 - 100 percent RH),
The Instrument Corporation
Tag-Heppenstall Moisture Tester, Model 8004
Analytical Balance (accurate to 0.1 mg.),
Central Scientific Company
Boerner Divider, Seedburo Equipment Company
Potentiometer (Direct temperature reading)
Leeds and Northrup
Various mercury-in-glass thermometers
Graduated cylinders
Burettes
Drying oven

(1°F),

37

EXPERIMENTAL METHODS
Thre© types of tests were made in this experiment; res­
piration tests, thermos-bottle tests, and comprehensive
tests*

The respiration tests were conducted under conditions

suitable for maximum mold growth.

The thermos bottle tests

attempted to duplicate conditions in a grain b i n .
The comprehensive tests were a series of tests to deter­
mine the effectiveness of irradiation in the reduction of
mold growth and to find what deteriorating effect irradiation
had on the quality of wheat for food.

These tests were more

complete than simple carbon dioxide measurements and fat
acidity determinations.

Also tests actually required in the

milling Industry were performed*
Respiration Tests
Five respiration runs were made, each run consisting of
eight samples that were kept in a respirab ion chamber at 86
degrees Fahrenheit for a period of 10 days.

These runs were

made with samples of approximately 150 grams of wheat per sam­
ple.

At the end of 10 days the wheat samples were analyzed

for the amount of carbon dioxide given off in 24 hours (test
for respiration) and tested for moisture by drying a small
sample in an oven for 72 hours at 212 degrees Fahrenheit.
Then the remainders of the samples were placed in storage
at 40 degrees Fahrenheit until shipped to the laboratory for

38

fat acidity determinations.
The first two runs were exploratory in nature to find
approximately what irradiation dosages were necessary to re­
duce total respiration to a level comparable with that of
very dry wheat (10.0 - 12.0 percent wet basis).
The irradiation doses for the first run were 0 rep,
130.000 rep, 261,000 rep, and 392,000 rep.

It was found

after 10 days that these doses had little effect upon res­
piration.

On a second run at 0 rep, 1,000,000 rep, 2,000,000

rep, and 3,000,000 rep respiration was affected to a consid­
erable

extent in all but 0 rep samples.

Runs three, four,

and five were carried out at treatments of 0 rep, 500,000 rep,
700,000' rep, and 900,000 rep to find out how effective these
doses were at 14.0 - 15.0 percent, 15.0 - 16.0 percent, and
15.0 - 17.0 percent moisture.
Of the eight samples in a run, four of the samples were
of low moisture' content

(approximately 10.0 - 12.0 percent

moisture content wet basis) and were used as a control.

The

other four were of high moisture content (14.0 - 17.0 percent)
The high moisture samples were in one of three ranges 14.0 15.0 percent, 15.0 - 16.0 percent, or 16.0 - 17.0 percent.
Moisture contents above 14.0 percent wet basis are not safe
for storage, whereas those from 10.0 - 12.0 percent moisture
are safe.

For each run of eight there were three levels of

irradiation.

(See Table VII.)

a series of four pairs:

The samples were arranged in

one pair with no treatment, one at

39

a low level of treatment, another at a medium level of treat­
ment, and a final pair at a high level of treatment.

Each

pair consisted of a sample at low moisture content and one
at high moisture content, (See Table VII.)
Table VII.
SAMPLES OP WHEAT FOR A RESPIRATION TEST

Moisture Content

Doses
no

High
Low

Sample 1
Sample 2

low

medium

Sample 3
Sample 4

high

Sample 5
Sample 6

Sample 7
Sample 8

The arrangement shown In Table VII. is known in statis­
tics as two-way classification.
By analysis of variance it is possible to determine if
there is a significant difference between sample 2 (low mois­
ture content, no dose) and sample 7 (high moisture, high dose)
at a certain level of significance,

or in this instance whe­

ther the effect of irradiation on high moisture wheat was com­
parable to keeping wheat at a low moisture content.
Method of selecting samples.

Two lots of wheat from the

1955 crop of hard red spring wheat were furnished by the In­
ternational Milling Company.

Lot No. 1 was used on the first

run and lot No. 2 for the remainder of the runs.

For the res­

piration runs a sample about two gallons in size, sufficient
for the run, was selected at random for the l o t .

This large

40

sample was split equally by a B o o m e r ‘Divider
Figure 8).

( see

One of these samples was split in half in

the Boerner Divider, and then each of these halves was again
split in half.

This would make four samples of about one

quart each and one sample of about one gallon. Each one
quart sample was poured into a gallon bottle, stoppered, and
placed in cold storage at about 40 degrees Fahrenheit.

The

remaining one gallon sample was sprayed with distilled water,
as explained under the section "Conditloning grain to the
proper moisture” page 42.

This gallon was placed in storage

at 40 degrees Fahrenheit, tested

for moisture after two days,

and sprayed again if necessary until the proper moisture lev­
els was reached.

Then this sample was split in the Boerner

Divider and each half sample split again,
samples.

making four quart

Next, each of these samples was placed in a four

gallon bottle.

The bottles were stoppered and placed in stor­

age at 40 degrees Fahrenheit.
A definite numbering system was used.

The first four

samples that were not conditioned with water were numbered
2, 4, 6, and 8.

The samples that were conditioned with water

were numbered 1, 3, 5, and 7.
diated.

Samples 1 and 2 were not irra­

Samples 3 and 4 received the lowest doses;

samples

5 and 6, the next; samples 7 and 8, the highest doses.
Each of these samples was handled in the following man­
ner after irradiation.

About 50 grams of wheat was used for

a moisture determination;

150 grams for a respiration run;

100 grams for a fat acidity determination;
thermos bottle test .

one pint for the

At the conclusion of the respiration

run the 150-gram sample was used to make a 50-gram moisture
determination and a 100-gram fat-acidity determination.
Moisture content was determined by finding the loss in weight
after drying 72 hours at 212 degrees Fahrenheit.
All samples were placed in storage at 40 degrees Fahren­
heit when not actually undergoing a respiration run, moisture
determination, or fat acidity determination.

Figure 8 . A Boerner Divider which
was used to make an equal and random
division .

42

Conditioning grain to the proper moisture.

It was

difficult to find wheat direct from the field with the de ­
sired moisture content for a given experiment.

Other inves­

tigators (5, 32, 34) have resorted to sprinkling the grain
with distilled water and waiting a few days for the grain
to reach

equilibrium before testing In a respiration run.
5
Bailey and Gujar compared wheat that had been sprinkled with
distilled water with grain that was naturally damp.
sults of this investigation are shown in Figure 9.

The re­
In this

experiment they had waited three days after wetting the grain
before testing in a respiration run.

There appeared to be

some difference in the rate of respiration, but it was not
gr eat .
In view of this work by Bailey and Gujar^, it was deci­
ded to sprinkle the grain to the desired moisture level and
then wait for the grain to come to equilibrium.
sprayer was used for sprinkling.

Usually,

A small fly

it took a week

for the grain to reach the desired level.
The average sample was conditioned in the following man­
ner:

it was sprayed with distilled water, poured into a

sealed container, and then placed in a cold storage room at
40 degrees Fahrenheit.

The following day a sample was tes­

ted for moisture on the Tag-Heppenstahl moisture meter.

The

moisture deficit from the selected moisture level was noted
and more water was sprayed on; then the sample was returned
to the sealed container and storage room:.

This procedure

43

was repeated until the desired moisture level was reached,
after which the sample was kept in the sealed container in
cold storage at 40 degrees Fahrenheit until tested for res­
piration*

The final moisture content was determined by dry­

ing in an oven for 72 hours at 212 degrees Fahrenheit and
finding the loss in weight.
COg per IQOgm
of‘“'dry matter
per 24 hrs
mg
14

12

10

urai s
at

Respiration of
hard spring
wheat incubated
at 38.8°G, for
four days.

pened sprihg
8

°12
13
14
15
16
Percent Moisture (wet basis)
. .
„
,
Fig*9 Graph showing the comparative activity of naturally
damp wheat ^nd wheat dampened in the laboratory three days
before being incubated,^

44

'4

i /

.

1

Ml
Figure 10.
Spr ay ing wheat wi th
di s t i l l e d water to condition it
to the pro per moi sture level.

Irradi a t i n g v/heat to the required d o s a g e .

All ir r a d i a ­

tion was pe r f o r m e d by the ele ctron accelerator described on
pages

29 - 32.

The

irradiation dosages were de te rmi ned by

the di stance f r o m the wi n d o w of the electr on accelerator,
the speed at w h i c h the samples pa ssed by this window,
the b e a m - o u t
era tor
els.

current.

by

and by

A conveyor b e n e a t h the electron accel­

w i n d o w could be rai se d and lowered to appropriate

lev­

Also the speed of the conveyor could be changed by a

simple

adjustment

be e n w o r k e d out

on the va ri a b l e - s p e e d gear box.

in advance

on a series

wh i c h could be c o n v erted into a series
currents,

Doses had

of mathem atica l curves
of speeds, bea m-o ut

and di sta nc es fr o m the window.

The

actual a d j u s t ­

m e n t of the e l e ctr on acc el er ator and conveyor was made by
Ri c h a r d Nicholas,

the operator.

The v/heat to be
nel in thick ness

irradia ted was

spread out

one wheat

on an a l umin um tray six inches wide and

ker­

45

inches long.

40

(see Figure
or

11).

; all persons

This t r a y held ahout one-half pint

The tray of wheat was placed on the con vey­
left the room,

e l e c t r i c a l l y after the machine
kil ovolts peak.
was

stopped;

was removed,

of wheat

At the

and the conveyor was started
reached the level of 1,000

con clu sion of the run the

conveyor

the electro n ac cel era tor was shut off;

the tray

and its contents poured into the appropriate

sample b ot tl e .

A n oth er tray had b e e n pr epa red meanwhile

it was pla ced on the conveyor.

and

This procedure was repeated

u nt il all samples ha d b e e n treated.

Fig ure

11.

The wheat

sample on the convey or ready
irradiated.

to be

46

Excluding carbon dioxide from the incoming a i r .

The

first flask A in Figure 6 was used to remove carbon dioxide
that might he in the atmosphere.

Air from the room was

drawn into the train of flasks by the displacement of cal­
cium chloride from the first gallon bottle D .

The barium

ion of barium hydroxide has a strong affinity for the car­
bonate ion and forms a very insoluble barium carbonate.

Car­

bon dioxide entering a solution of barium hydroxide first
forms carbonic acid and then ionizes to form hydrogen and
carbonate i ons .

The carbonate ion combines with the barium

ion to form the precipitate barium carbonate.

This reaction

will take place to eliminate completely carbon dioxide in the
incoming air provided that there is an intimate mixture b e ­
tween the air and the barium hydroxide.

It is easy to pro­

vide an excess of barium hydroxide, but difficult to make an
intimate mixture between the incoming air and the barium hy­
droxide solution.

To a large extent the intimacy of the mix­

ture depended Upon the size of bubble passing through the b a ­
rium hydroxide solution.

This in turn depended upon the rate

at which air passed through the system.

In this particular

case the rate of air passage averaged 2.4 liters per 24 hours
or about 1 2/3 milliliters per minute.

The bubbles coming

through seemed small.
No test was made of the efficiency of this method in
excluding carbon dioxide, but it is estimated that carbon
dioxide in the air had little influence on the results.

47

The content of carbon dioxide in air varies from place
to place and time to time, but averages about 0.03 millili­
ters per liter.

This should not decrease the accuracy ex­

cessively, as measurements of carbon dioxide to approximate­
ly plus or minus one milliliter per liter were made in these
tests.

The solution in the first bottle A removed any ex­

cessive carbon dioxide.
Maintaining the wheat samples in the respiration
chamber at a constant moisture level.

The moisture content

of atmospheric air varies considerably from day to day and
from one part of the year to another.

In addition, as the

air Is heated from about 77 to 86 degrees Fahrenheit (as it
generally was in this experiment) the relative humidity b e ­
came lower.

In this experiment it was desired that wheat be

kept at four ranges of moisture content:

between 14.0 - 15.0

percent, 15.0 - 16.0 percent, 16.0 - 17.0 percent, and 10.0
- 12.0 percent.
It was necessary to condition air that was drawn over
the samples in order to prevent the air from changing the
moisture content of the wheat.

Coleman and Fellows

11

tested

a number of wheats to determine the equilibrium conditions
between the moisture content of wheat and the corresponding
relative humidity.

Their work on hard red spring wheat is

listed in Table VIII.

48

Table VIII.
MOISTURE CONTENT OP HARD RED SPRING WHEAT IN EQUILIBRIUM
WITH VARIOUS RELATIVE HUMIDITIES11

Moisture Content of
Hard Red Spring Wheat
Dry Basis
%
7.27
9.25
11.21
13.40
17.32
24.61
33 .42

Wet Basis
%
6 .71
8.47
10 .08
11.8
14.7
19.7
25 .0

Relative Humidity
of Atmosphere
%
15
30
45
60
75
90
100

In order to maintain a moisture content of a wheat sam­
ple throughout a respiration test run it was necessary to
maintain the relative humidity in accordance with the results
shown in Table VIII.
have been costly.

To have done this mechanically would

A salt solution will maintain a certain

vapor pressure depending upon the chemical, its concentration,
and its temperature.

The easiest method of attaining a con­

stant concentration was to maintain saturated salt solutions
by placing an excess of salt in the solution.

The difficulty

with this method was that the saturated salt solution that
came nearest to maintaining the desired relative humidity
would not have been close enough.
Table IX.

This can be seen in

49

Table XX.
RELATIVE HUMIDITY OF A FEW SATURATED SALT
SOLUTIONS HELD AT 30°C
(From International Critical Tables, Volume 3,pp.351-85)

Saturated Salt

Vapor Pressure
m m . of H g .

Relative Humidity
at 30°G %

3.56

10.8

LiCl*H20
MgClg *6HgO

10.3

32.4

MnClg *4HgO

17.0

51.8

CuCl2

21.52

65 .5

KOI

26 .9

81.8

NaCl

23.9

72.7

In order to

make use of the material in Table VIII

it

was plotted on a

graph as shown on Figure 12. From this

fig­

ure

it can be seen that to maintain a moisture content of

16.0 - 17.0 percent a relative humidity between 80 - 84 per­
cent must be maintained; for wheat of 15.0 - 16.0 percent
relative humidities between 75 - 80 percent; for wheat of
14.0 - 15.0 percent relative humidities between 70 - 75 per­
cent; and for 10.0 - 12.0 percent wheat, relative humidities
between 47 - 62 percent. Table IX revealed that a saturated
solution of potassium chloride was in equilibrium at 81.8
percent relative

humidity and therefore could be used for

maintaining wheat between

16.0 - 17.0 percent moisture.

In

a similar way sodium chloride could be used for maintaining
wheat between 14.0 - 15.0 percent.

Inasmuch as potassium

50

chloride solution could maintain a relative humidity of
81,8 percent and this was very close to the 15.0 - 16.0
percent moisture level, it was used for maintaining this
level in the experiment.
The average inside air in the room surrounding the
respiration chamber averaged 70 degrees Fahrenheit at 50
percent relative humidity.

If this air was heated to 86

degrees Fahrenheit it would have a relative humidity of
about 29.7 percent.

This is about right for 8.5 - 9.0 per­

cent wheat which is close to 10.0 - 12.0 percent moisture.
Therefore, the air for the 10.0 - 12.0 percent wheat was
passed over water containing a dilute solution of sodium
chloride.
In summary, the following solutions were used to main­
tain moisture of wheat at the required levels:
16.0 - 17.0 percent
15.0 - 16.0
14.0 - 15.0
10.0

-

12.0

ii
ri
ii

Saturated KG1
ii

KC1
NaCl

Dilute NaCl

Percent
Moisture
(Wet .
Basis)
20

A
Data from Co
and Fellows

10%

‘

■*

'

•

dot' ' +5i

Relative Humidity of the air
F i g # 12 Equilibrium humidities of hard red spring
wheat at various moisture levels*

52

Maintaining a constant air supply.
section entitled 'Rate of air supply*

According to the

(page 15), it could be

expected that the maximum rate of mold growth would be at about 20,0 milliliters of air per day per gram of dry matter.
If the samples were approximately 125 grams of dry matter
each, then there should have been (20.0) (125) or 2,500 mil­
liliters of air supplied per day per sample.
A constant supply of air was obtained by allowing a con­
centrated solution of calcium chloride to drain from a gallon
bottle at a constant rate.

The displacement of the solution

sucked in air, which passed through the train of bottles,
consisting of the Erlenmeyer flask that removed the carbon di­
oxide from the incoming air, the Erlenmeyer flask that main­
tained a constant relative humidity, and the Erlenmeyer flask
that contained the wheat sample .
In Figure 6 the operation of the air supply system can
be seen.
rate.

Time clock F allowed the tube b to drop at a fixed

The level of tube b determined the level in gallon

bottle D .

As tube b was lowered, the excess solution of cal­

cium chloride solution drained over into bottle E,

The rate

at which b fell determined the rate at which air passed
through the system.

The time clock determined the speed at

which the tube fell, and therefore it determined the rate at
which air passed through the wheat sample.

As a result it

was necessary only to use the right size of pulley on the
time clock to control the rate at which the air passed

through the system.
The total quantity of air that passed over the wheat
could be measured if the solution of calcium chloride were
measured and if the air passing into bottle D were at atmos­
pheric pressure.

The solution passing into bottle E could

be measured to the nearest milliliter by means of volumetric
flasks and graduated cylinders, and by calibrated dip sticks
to the nearest 20 milliliters.

In gallon bottle D the pres­

sure could be determined by observation of the tube level
above the solution level in Erlenmeyer flask A.

It was ob­

served to be never more than one-quarter inch different from
the solution level.

As the atmospheric pressure was fair iy

close to 29.0 cm of mercury, one-quarter inch of water was
approximately (29.0)

(13.6)

(2.54) (4) or one part in 4,000,

a negligible amount.

ML

¥

A

i1
4 .4

Jf’*

kI
Figure 13.

¥ ■

Filling gallon bottle D of respiration chamber

54

It was necessary to refill bottle D each day (Figure 11)
to repeat the experiment for another 24 h o u r s .

This refil­

ling was accomplished by closing pinch cocks at J and K and
opening the pinch cock at L.
at H.

New solution was then admitted

This operation can be seen in Figures 13 and 14.
Calcium chloride solution was used, as carbon dioxide

is only slightly soluble in calcium chloride solution.

In­

asmuch as carbon dioxide was the gas to be measured to deter­
mine the rate of respiration,
tle be lost.

it was essential that very lit­

A test was made of the set-up in the experiment,

disclosing that approximately 0.7 milligrams of carbon diox­
ide was absorbed into the system each 24 hours.

This amount

was for new solution; for solution that would be in contact
with carbon dioxide every day, a_s it was in this experiment,
the amount1absorbed would be even less.
Determination of carbon dioxide content.
plained previously in the section 'Respiration'

As was ex­
(page 5),

the rate at which wheat respires can be determined by the
quantity of carbon dioxide given off.

In this experiment

the quantity of carbon dioxide given up was measured for a
24-hour interval and was used as an index of deterioration
and condition of the wheat.
When carbon dioxide is passed through a solution of
barium hydroxide, the carbon dioxide first goes into solu­
tion forming carbonic acid, and then the carbonate radical
combines with the barium ion to form the very insoluble

55

barium carbonate.

The completeness of* this reaction is de­

termined by the intimacy the carbon dioxide reaches with the
solution.

The total quantity of* carbon dioxide that passed

into the solution could be determined in these experiments
by measuring the remaining hydroxyl-ion concentration of a
known original quantity and normality of barium hydroxide,
if the carbon dioxide is sufficiently mixed with the barium
hydroxide solution, all of the carbon dioxide will go into
solution and form insoluble barium carbonate.
C02 -}- H g O —
h 2^03 —

That is,

H 2C03

I— Ba(-0H)2 — *-BaC03

2HgO

The remaining barium hydroxide will be that which is
not precipitated by the carbon dioxide.

The difference b e ­

tween the original quantity of barium hydroxide and that re­
maining which did not combine with the carbon dioxide is the
amount.that had combined chemically with the carbon dioxide.
With the chemical equation for combination of carbonic acid
and barium hydroxide known, the total quantity of carbon
dioxide combined can be found.
The method of using barium hydroxide to precipitate
carbon dioxide and titrating the residual barium hydroxide
against an acid of known normality was the method used by
Bailey and Gujar

in their classical experiments to deter­

mine the respiration of wheat.
In order to determine the normality of the barium
hydroxide accurately,

it was titrated against a carefully

56

prepared solution of potassium acid phthalate each time a
respiration test was m a d e .

Also the barium hydroxide was

titrated against the hydrochloric acid in the experiment to
standardize the hydrochloric acid.

Both of these titrations

were triplicated to ensure accuracy.
Potassium acid phthalate was used as a standard, first
because it does not change greatly with time, and secondly
because owing to its large atomic weight (204.0), it is re­
latively easy to use in making an accurate normal solution.
Dilute solutions of both barium hydroxide (usually about
.05 normal) and hydrochloric acid (usually about

.10 normal)

were used to increase the accuracy of reading the burette
during titration.
Method of obtaining a respiration sample.

Generally a

one-liter sample of air at atmospheric pressure was the size
of sample for respiration determination that was drawn from
the sir that had passed over the wheat.

As was explained in

the section "Maintaining a constant air supply" (page 53),
the total air passed over the sample in 24 hours was collect­
ed

in bottle D (Figure 13) .

The air that had collected in

this bottle was at atmospheric pressure or slightly below
(perhaps one-quarter inch of water below atmospheric pres­
sure).

A sample of one liter was drawn by closing pinch

cocks J and K, filling one liter of calcium chloride solu­
tion through H and drawing out one liter of the air at point

57

L (see Figure 14).

Previously, the one liter Erlenmeyer

flask N had been filled with one liter of distilled water.

Just before collecting a sample
in bottle K*

After collecting sample in bottle N

Fig. 14 Method of obtaining a respiration sample

58

The calcium chloride solution in volumetric flask M forced
the air out of bottle D' at the same time the distilled water
drained out below sample bottle N and helped draw in the sam­
ple .

If exactly one liter of distilled water was placed in

sample bottle N and one liter of calcium chloride solution
was placed in volumetric flask M, then a liter of air would
be drawn out of the bottle D into sample bottle N.

Allowance

was made for the volume of tubing.
This method of drawing air over wheat and collecting a
sample of air was similar to the methods used by Milner,
Christensen, and Geddes (1947)3^, Matz and Milner (1951)^2,
and Bottomley, Christensen,and Geddes (1952)

.

Measuring the respiration of a sample of w h e a t .

After

drawing the sample as explained in the section ’’Method of
obtaining a respiration sample” (page 56), thirty milliliters
of barium hydroxide solution of about 0.05 normality was add­
ed

to the sample of air drawn.

This was done by filling a

50-milliliter burette exactly full, placing the tip end in
one of the rubber tubes, opening the pinch cock on the rub­
ber tube, opening the valve on the burette, and allowing ex­
actly 30 milliliters to flow into the flask.
be seen best by observing Figure 15.

This method can

When the flask had been

filled to 30 milliliters, the pinch cock on the rubber tube
was closed and the burette withdrawn.

There

were now 30 mil­

liliters of barium hydroxide in contact with the sample of

59

air containing the carbon dioxide.

The sample bottle was

slightly above atmospheric pressure owing to the addition of
the 30 milliliters of barium hydroxide.

The increased pres­

sure helped precipitate the barium carbonate.

Then the sam­

ple bottle was vigorously shaken up and down two hundred
times to ensure that all carbon dioxide would be taken out
of the air sample .

It can be seen that there is an advantage

to this method as compared to collecting carbon dioxide by
passing it once over a solution as is sometimes done.

The

method described here ensures precipitation of almost all
carbon dioxide as a carbonate.

!

Figure 15. Adding 30 milliliters of
Ba(0H)g to the sample.

60

The stopper on the sample "bottle w a g now opened, and
distilled water was used to v/ash down the inside of the sam­
ple bottle to ensure that all of the solution would be titrat­
ed^

Two drops of phenolphthalein were added and the solu­

tion titrated against hydrochloric acid of about 0,1 normali­
tyThe total quantity of carbon dioxide was calculated as
shown in the section "Determination of carbon dioxide con­
tent"

(page 54).

The total carbon dioxide respired was:

Total carbon dioxide
/Total air passed^ /Carbon dioxide\
respired by sample
(over wheat in 24/(present in
J
of wheat in 24 hours - [hours in ml.
/\1,000 ml.
/
lTOOO
Usually, the respiration rate of wheat is given in mil­
ligrams of carbon dioxide per 24 hours per 100 grams of dry
matter.

Since there was on an average 125 grams of dry m a t ­

ter, a correction had to be made for this difference.
Errors in determining the rate of respiration.
od

The meth­

of determining the rate of respiration or the quantity

of carbon dioxide in a sample of air is subject to many pos­
sible errors .

The greatest error would be that not all the

air was thoroughly mixed with the solution of barium
ide

hydrox­

, and consequently some of the carbon dioxide would es­

cape and not be measured.

A second possible source of error

was that some of the carbon dioxide would be absorbed into
the solution of calcium chloride in which it was in contact.

61

There were several other possible sources of error, such as
inaccurate measurement of solutions and volumes, and losses
in t u b i ng.
It was decided to check the method against a known quan­
tity of carbon dioxide.
shown in Figure 16,

This was done with the apparatus

A quantity of dry ice was weighed care­

fully inside a small insulated box on an analytical balance.
As soon as it was weighed it was quickly dropped in the gal­
lon bottle A, of Figure 16.

Bottle A was stoppered quickly

in order to maintain atmospheric pressure,and test tube B was
lowered until the level of solution in the test tube was the
same as that in the graduated cylinder.

Then calcium chlor­

ide solution was allowed to enter gallon bottle A from gallon
bottle C by opening the two pinch cocks d and e.

Two samples

of air were then removed from bottle G by the method explained
in "Method of obtaining a respiration sample" (page 56).
These were immediately mixed with barium hydroxide according
to the method given in "Measuring the respiration of a sample
of wheat" (page 61), and the quantity of carbon dioxide d e ­
termined for two samples.

Again after the sample had been

In contact with the solution for 24 hours, two more samples
were taken.

A comparison was made between the quantity of

carbon dioxide obtained by titration and by weighing the dry
ice.

A second comparison was made between the carbon dioxide

found by titration immediately after placing the dry ice In
the bottle and the amount found by titration 24 hours later.

62

These results are shown below:
13.25 milligram proportion of dry ice per 900 milliliters
of air
First sample 15.2 milligrams
Second

M

15 .5

11

First sample 14.5 milligrams
Second

M

14.7

11

Determination of GO2 psr 900
milliliters by titration immediately after transferring in
bottle C.
Determination of COg per 900
milliliters by titration 24
hours later.

It can be seen there was not a great difference in any
of the two.

Actually, the titration shows slightly more than

the actual method by wei g h t .

There was slightly less carbon

dioxide after 24 hours than before.
A second test was performed with the results shown be ­
low :
19.6 milligram proportion of dry ice per 900 milliliters
of air
First sample 16.3 milligrams
Second

"

15.6

11

First sample

13.8 milligrams

Second

a failure

n

Determination of COg per 900
milliliters by
titration.
Determination of COg per 900
milliliters by titration 24
hours later.

From the results it can be seen that the determinations
by titrations were more consistent than those by weight.

It

is believed that some water condensed on the dry ice in some
cases and led to errors in the determinations by weights.

To

avoid this, samples were cut from the interior of a piece of
dry ice .

63

Prom these results an idea of the error in reporting
carbon dioxide respired can be obtained.

Pig. 16

Apparatus for determining total errors for
rate of respiration.
Thermos Bottle Tests

A series of tests was made with pint thermos bottles.
The purpose of these tests was to duplicate as nearly as
possible ..conditions in a wheat bin.

As far as heat transfer

is concerned, a perfectly insulated surface has the same ef­
fect mathematically as an infinite quantity of wheat.

In

other words, from a heat transfer standpoint the wheat in
the thermos bottle should be in conditions similar to a sam­
ple in the top and center of a large wheat bin.

The greatest

difference between a true wheat bin and the thermos bottle is
that eration is possible only from the top of a

64

thermos bottle .
air f l o w .

The sides and bottom contribute nothing to

Under these conditions molds and anaerobic micro­

organisms will develop that are not characteristic of condi­
tions in grain bins .

A second difference occurs because the

vacuum bottle is not a perfect insulator.
ertheless,

It was hoped, nev­

that these tests would approximate the conditions

in a wheat bin.
The samples for these tests were all obtained from a
division of those used in the respiration run.

Therefore,

the method of selecting the samples, conditioning them, and
testing for moisture were the same.

Also, they were irradi­

ated in the electron accelerator before they were divided.
After irradiation a division was made for those undergoing
a respiration test and those used to form a thermos bottle
test.
The thermos bottle tests were performed by filling eight
pint-size thermos bottles with wheat of the same test classi­
fication as those for the respiration run.

For example, each

respiration run consisted of eight samples which up to and
including irradiation were the same as the thermos bottle
samples.

At this point the samples were divided and for each

respiration sample there was a thermos bottle sample.

The

thermos bottles each had a copper-constantan thermocouple
placed in the bottom of the bottle before filling with w h e a t .
The eight thermos bottles were then placed in a room kept at
87 degrees Fahrenheit and were kept at this temperature for

65

20 d a y s .

Thermocouple temperatures were read on the second

day and every other day until the conclusion of the run.

At

the end of the run each sample was poured into a separate
paper "bag and kept at 40 degrees Fahrenheit or below until
shipped for fat acidity determinations.
Each thermocouple was calibrated in the following man­
ner.
ed

A pint thermos bottle was filled with water and adjust­
to a temperature of 87 degrees Fahrenheit on a mercury

thermometer which had been calibrated with a certified ther­
mometer.

The thermocouple was placed in the solution, the

water was constantly stirred for about three minutes, and a
reading on the potentiometer was compared with a reading on
the calibrated thermometer.

Usually, there was net more than

a half degree Fahrenheit temperature difference in reading
the thermocouples.
Comprehensive Tests
Respiration run for comprehensive tests. During the
respiration tests it was found that at doses of 900,000 rep
the respirations in high moisture content wheat, when subjec­
ted to a ten-day test at 86 degrees Fahrenheit and 16.0 20.0 milliliters of air per gram of dry matter, were nearly
the same as those in very low moisture content wheat.

This

seemed to indicate that mold activity was at a-low level and
hence spoilage should be low.

For this reason it ,vas decided

to compare a series of moisture levels at no irradiation and

irradiation at 900,000 rep.

The moisture levels decided upon

were 10 - 12 percent, 14 - 15 percent, 15 - 16 percent,
16 - 17 percent

on

a

wet

basis.

and

These were the same

moisture levels of wheat used in the regular respiration run.
Moisture determinations were made by drying 72 hours at 212
degrees Fahrenheit and finding the change in weight. The gen­
eral set up of the samples is given in Table X.
Table X .
NUMBER OF SAMPLES FOR COMPREHENSIVE TESTS

Moisture Percentage of Wheat (Wet Basis)
Doses
rep
0
900,000

10 - 12%

14.0 - 14.9$
one
one

one
one

15.0 - 15.9$

16.0 - 16.9$

one
one

one
one

The samples selected for the comprehensive test were
from the same lot of wheat as those for repiration runs N o s .
2, 3, 4, and 5.

These samples were selected by choosing a

sample of wheat of about 20 pounds.

This was subsequently

divided in the Boerner Divider into halves; then each half
again was split and so on until there were eight samples of
about 1,200 grams each.
The samples were conditioned to bring them to the de­
sired moisture level.

This was done in the same manner as

those for the respiration run as explained on pages 42 and
43 .
All samples were subjected to a 10-day test at 87

67

degrees Fahrenheit and an aeration rate of about 16.0 milli­
liters per gram of dry matter to check thoroughly the pre­
ceding respiration and fat acidity determinations in order
to see if 900,000 rep were effective in reducing the spoil­
age of wheat by molds .
Milling and baking tests .

All tests were performed by

the International Milling Company of Detroit, Michigan.

They

followed the procedures of Cereal Laboratory Methods, 5th
edition, of the American Association of Cereal Chemists.
The baking method was an intermediate sponge and dough
method, employed routinely in the International Milling Com­
pan y ’s laboratory.
The wheat was ground in a Buhler mill.

A five-pound

sample was weighed, tempered to 16 percent moisture^ and al­
lowed to stand for approximately 18 hours, at which time it
was run through a laboratory Buhler mill at the rate of about
five pounds in 12 minutes.

The flour was collected and weighed,

and the percentage yield calculated on a wheat input basis.
Likewise, the bran and shorts were separated and similarly
calculated.

68

ANALYSIS AND RESULTS
Th ree.distinct types of tests were analyzed:

the res­

piration tests, the thermos "bottle tests, and the comprehen­
sive tests.
iment

The respiration tests were an accelerated exper­

conducted at optimum conditions for rapid mold growth.

The thermos bottle tests attempted to reproduce conditions
in a grain bin.

The comprehensive tests reproduced conditions

for rapid deterioration of wheat and tested conditions of no
treatment against the treatment that had been most effective
in reducing respiration.

Finally, the comprehensive tests

included most of the standard milling tests such as dry mat­
ter, percent bran, percent shorts, milling time, baking tests,
odor, taste, etc.
Analysis of Respiration Tests
The respiration tests consisted of five runs of ten days
duration at 86 degrees Fahrenheit.

From 16.0 - 20.0 millili­

ters of air per gram of dry matter were passed over the wheat
per day.

The amount of carbon dioxide respired on the tenth

day was used as a criterion to determine the rate of deteri­
oration of wheat.

Fat acidity determinations were made of

these samples of wheat both before and after each run for the
third, fourth, and fifth runs.

These data were likewise ana­

lyzed .
The first,

second, and third respiration runs were

69

exploratory in nature,

It was known that dosages up to

1,000,000 rep were required to kill certain molds completely.
Since doses of 100,000 rep cause a 99.98 percent mortality
of certain molds, it was believed that doses in these lower
ranges would be effective in reducing the activity of molds
to a low level.
The fourth and fifth runs were to determine how effec­
tive treatments were in the ranges of 500,000 to 900,000 rep.
The experiments revealed that these ranges of doses reduced
production of carbon dioxide.
Analysis of the first respiration r u n .

The first res­

piration run was conducted at 0, 130,000 rep, 261,000 rep,
and 392,000 rep.

Two levels of moisture in wheat were tested,

one between 11.9 - 12.2 percent and the other between 16.6 16.9 percent.
XI

The results of this test can be seen in Table

and Figure 17.

This was purely an exploratory run.
Table X I .

RESULTS OF THE FIRST RESPIRATION RUN

0 rep
Moisture con­ 16.6 12.2
tent at start
(Wet basis)
X X . 95 13.65
Average air
in m l . per
day/lOOgrD ,M.
"0Q2Eig/lOOgr
35.3 13.1
D .M ,10th day

130,000
16.9 11.9

261,000
392,000
T6.7
12.05 16.85 12.1

14.95 15.1 ' 14.41 13.''2"" 1 5.X T3Y3
35.5

14.0

35.3

11.6

35.1

14.0

70

mg
Production
of
3a
COg
per
2(>
100 gm
dry matter
per 24 hrs
ot
0

16«6-16»9 % Moisture
■^ ■o —
---

X /£l«9-12 ,2^A*Moi31ure
100,000

200,000 3t)0,000 4’00,000

Treatment in rep
Fig. 17

Production of COg vs. Treatment--Run One

The method of analysis of variance was used to ana­
lyze these data (see Table XII ).
Table XII.
ANALYSIS OF VARIANCE COg PRODUCED 10th DAY--FIRST RUN

Siam of Squares

Mean
d.f . Square

Moisture Means
Treatment Means
Residual

974 .4
1.4
2.8

1
3
3

Total

978.6

7

It can be seen from Table XII

F

F .95

974.4 1047.7
.47
.505
.93

10.1
9.28

that there is a definite

difference in respiration rate between the moisture means of
the wheat at 12.1 - 12.2 percent and 16.6 - 16.9 percent,
but practically no difference in the rate between treatment
means.

This can be seen best from Figure 17.

It was conclu­

ded for this set of conditions that the doses applied had no
significant^effect upon reducing the production of carbon

71

dioxide.

Higher doses were necessary.

Analysis of the second respiration r u n .

Inasmuch as

doses up to nearly 400,000 rep were not successful in reduc­
ing

the production of carbon dioxide, it was believed neces­

sary that a much wider range of doses should be given.

This

was done in the hope that a pair of doses would bracket the
position where carbon dioxide production was reduced.

Wheat

samples at nearly the same range of moisture levels at the
previous run were given doses of 0, 1,000,000, 2,000,000, and
3,000,000 rep.

This wheat was hard red spring wheat from

the fall harvest of 1955, but of a different lot from run
number o n e .

All the remaining runs were carried out with

this second lot of wheat.
The results of the second respiration run are shown on
Table XIII

and Figure 18.
Table XIII.
RESULTS OF THE SECOND RESPIRATION RUN

0 'rep
Moisture con­
tent at start
(Wet basis)
Average air
in ml. per
day/lOOgrD,M.
C02mg/lOOgr
D .M .10th day

16.7

1,000 ,000

12.8 16 .6 12.8

2,000 ,000
16 .5

12.8

3,000,000
16.8

11.9

14.71 13.9 14.1 14.45 15 .55 15.05 15.65 15.15
16.2

3.9

4.4

3.9

5 .0

1.72

0

0

Respiration is zero at the 3,000,000 rep level for both

72

the high mcpisture content wheat and the low moisture content
wheat.

Evidently at this point both the molds and enzymes

were neutralized.

At the 1*000,000 rep level there was not

a great deal of difference in carbon dioxide production of
the wet wheat and the dry wheat of no treatment.

An analy­

sis of variance was made to determine at what level of sig­
nificance there was a difference in the treatment means at
0 rep and 1,000,000 rep.

A moisture content between 11.9 -

12.8 percent was used as one level and 16.5 - 16.8 percent
moisture as the other level.

The results of the analysis

of variance are shown below.
Table XIV.
ANALYSIS OF VARIANCE FOR C02 PRODUCED ON 10th DAY--SECOND RUN

Sum of Squares

d.f .

Moisture Means
Treatment Means
Re sidual

32 .31
104.85
48.84

1
3
3

Total

186.00

7

mg.
Production
15#
of
per
100 gm.
dry matter
per 24 hrs

16.5-16

Mean
Square
32.31
34.95
16.28

F
1.98
2.15

moisture

11.9-12

moisture

5.
0

2x10
1x10
Treatment in rep'

3x10

Fig.18 Production of C02 vs. Treatment— Run Two

P .95
10.1
9.28

73

There was no difference in moisture means or treatment
means at the five percent level of significance.

However,

there was a difference in wheat net treated and wheat treated
at 1,000,000 rep at high moisture according to the t test.
There may he some criticism of making a t test when the treat­
ment means show no significant difference; however, according
pp
to Goulden
, ”lt is valid to make any t test provided that
the test is preconceived at the time the experiment is de­
signed.”

A comparison of this type had been contemplated

before making the experiment.
- I 2(16.28)
I -------- * 5.68
\
1

The standard error of a mean
difference .

We shall compare the treatment means at 0 and 10
16.2 mg. COg
4.4 mg. CO^

at
at

0

rep.

0 rep
1,000,000 rep

16.2 - 4.4
t = ----------- - - 2.08
5 .68
t r

1.64 for three degrees of freedom at the 20
percent level of significance.

Prom the results of runs one and two it would appear
profitable to explore the possibilities between 400,000 rep
where there was no effect and 1,000,000 rep where there was
an effect .
Analysis of the third respiration r u n .

Since doses

of 1,000,000 rep had an effect on reducing the respiration

74

and doses of 392,000 rep had no effect, it was decided to
test doses of 500,000, 700,000, and 900,000 rep, respectively.
The results of the third respiration run can be seen in Table
XV.

Two air samples were taken and tested for C02 •
Table XV.
RESULTS OF THE THIRD RESPIRATION RUN

0 rep
Moisture con­
tent at start
(Wet basis)
C02mg sample
/lOOgr
1st
D.M.
lOthdav
2nd
"p-pPA Fn-h-hy)
acid 10th
day mg .KOH
/lOOgm D.M.

500,000

15.65 11. 3 15.5

700,000

900,000

11.3

15.5

11.7

15.9

11.3

15.9

1. 9

4.1

3.8

1.7

0.2

1.3

0.7

13.1

3. 3

6.5

3.8

4.0

3.0

3.9

3.2

13. 7 14.2

15.5

15.4

13.0

16.0

14.2

16.0

An analysis of variance for the carbon dioxide test on
the 10th day is given in Table XVIa and the same is shown in
Table XVII

for the free fatty acid test on the 10th d a y .
Table XVIa.

ANALYSIS OF VARIANCE OF C02 PRODUCED ON 10th DAY --THIRD RUN

S .3 .

M.S.

1
3
1
3
7

7.84
105.96
58.52
92.95
7.40

7.84
35.32
58.52
30.18
1.06

15

272 .67

d.f .
Replications
Treatments
Moisture
Interaction
Error
Total

F*

P .95

0.26
1.17
1.93

5 .59
4 .35
5 .59

Interaction mean square used as the denominator for the F ratio.

75

Since the interaction mean square was significantly
larger than the error mean square, the interaction mean
square was used for making tests in Table XVIa as to whether
treatment mean square and moisture mean square were signifi­
cantly different from interaction mean square. According to
the P test it can be seen that there is no significant dif­
ferences in moisture means nor treatment means.
In order to exclude the effect of the large interaction,
analyses of variance were made for both high moisture wheat
and low moisture wheat.

These analyses are shown in Tables

XVIb and X V I c .
Table XVIb.
ANALYSIS OP VARIANCE OP COg PRODUCED ON 10th DAY--THIRD RUN
HIGH MOISTURE ONLY

d.f.

S.S.

Replications
Treatments
Error

1
3
3

3.3
187.7
9.6

Total

7

200.6

M .S .
3.3
62.3
3 .2

F
.10
19.47

p .95
10.13
9.28

Table XVIc
ANALYSIS OP VARIANCE OP COg PRODUCED ON 10th DAY--THIRD RUN
LOW MOISTURE ONLY
d.f.

S.S.

M .S .

Replications
Treatments
Error

1
3
3

5.5
5.6
1.5

5.6
1.9
0.5

Total

7

13.7

p

F.95

3.8

9.28

76

According to the F test there is no significant differ­
ence between treatments at low moisture.

1st sample 15.5-15.9^ moisture
2nd sairrole 15 ,5-15 .9/o
0

Production
of
COg
per
100 gm
dry matter
per 24 hrs

-l.3t__aiimp.le.

,

7fo
moisture

500,000
700,000
Treatment in rep

Pig.19 Production of COg vs.Treatment—

900,000

Run Three

According to the F test there was a significant difference
between treatment means at the five percent level of significance
for high moisture.

Carbon dioxide
respired per 24hrs
Average of
0 rep treatment at high moisture 14.5
"
,f
500,000 "
"
11
"
“
5.3
11 700.000
rl
11
11
11
Tl
2.9
"
n
900,000 "
”
‘
11
2.6
2 (3 .2 )
-

1.79

The standard error of a mean difference.

Comparing 0 rep treatment with 500,000 rep treatment.
14.5 - 5.3
- 5.13
1.79
Comparing 500,000 rep treatment with 900,000 rep treatment.
5.3 - 2.6
1.51

t 1.79
t =

2.36 for seven degrees of freedom at the five percent level
of significance.

From these comparisons there was at the five percent
level of significance a difference between 0 rep treatment
and the 500,000 rep, 700,000 rep, and 900,000 rep treatments,
but none between the 500,000 rep, 700,000 rep, and 900,000
rep treatments.

(A significant difference was shown between

the two extremes at 500,000 and 900,000 rep treatments.
Consequently, there must be no significant differences at the
700,000 rep treatment and the 500,000 and 900,000 rep treat­
ments . )
Analysis of variance was made for the free fatty acid
test at the end of the run, the results appearing in Table
XVIII .
Table XVII.
FREE FATTY ACID (mg .KOH/lOOgm D.M.)--END OF THIRD RUN

Moisture#
Wet
Basis
Low moisture
11.3 - 11.7#
High moisture
15.5 - 15.9#

Treatment in reps
0

500,000

700,000

900,000

13.7

15.5

13.0

14.2

16.0

14.2

15 .4

15.0

77

Table XVIII.
ANALYSIS OP VARIANCE OP FREE PATTY ACID -- END OP THIRD RUN

Sum of* Squares

d.f*.

3.38
.89
84.53

1
3
3

Moisture Means
Treatment Means
Re s idual
Total

88.8

Mean
Square

F

3.38
.30
28.17

^,95

.120
.011

10.1
9.28

7

Clearly there is no difference in treatment means and
moisture means.

The free fatty acid determinations evidently

are not sensitive enough to show any distinct differences.
There seem to be no more profitable comparisons.
Analysis of the fourth respiration run.

Because the

treatments at 500,000, 700,000, and 900,000‘rep had shown
excellent results so far as respiration was concerned, it
was decided to test these treatments at a slightly lower
level of moisture.
Table XIX

The results of this test appear in

and Figure 20.
Table XIX.
RESULTS OF THE FOURTH RESPIRATION RUN

500, C00
rep
0 :
Moisture content
% at start
14.3 10.8 14.1 10.9
(Wet basis)
COgmg/
Sample
1.0
lOOgrD.M.
1st 1.9 1.05 1.0
1.4
10th day
2nd 2.6 1.05 3.0
Free fatty acid
10th day mgKOH/ 14,8 13.1 13.0 13.0
lOOgm.D,M.

^00, 000
14 .2

10.9

2.0
2.1

2.4
1.9

13.7

11.9

900,000
14.3 10.8
0.0
1.8

2.6
3.1

14.2 11.9

78

10.Gmg
Production
(10.8-10.9)
(14.1-14.3)
of
Q Is t sample low moisture olst sample high
COg
5.0- A 2nd sample low moisture? / x2nd sample hio-h
per
100 g m .
dry matter
per 24 hrs
0.0
j—

i

500,000

r

700,000

900,000

Treatment in rep
Pig* 20

Production of COg vs. Treatment--Run Pour

The amount of carbon dioxide produced in the fourth run
was analyzed by the method of analysis variance in Table XX.
Table XX.
ANALYSIS OP VARIANCE FOR COg PRODUCED ON 10th DAY--FOURTH RUN
”
Sum of Squares
Replications
Treatment Means
Moisture Means
Interaction
Error
Total

d.f .

1.56
0.65
0.00
5 .89
2 .48

1
3
1
3
7

10.56

15

Mean
Square
1.56
.21
0.00
1.96
.35

F
4.45
.60
.00
5 .60

P .95
5.59
4.35
5.59
4 .35

Only the interaction was significant at the five percent
level for the F test.

Evidently, the low moisture content

did not produce any significant change.

Apparently, below

15.0 percent moisture wheat will keep safely without treat­
ment, a fact proved true in practice.
Analysis of variance was applied to the free fatty acid

testa made at the end of the run, the results appearing In
Table XXII.
Table XXI
FREE PATTY ACID (mgKOH/lQOgr .D .M .)--END OF FOURTH RUN

_______ Treatment in reps
___________________________ 0
Low Moisture Content
10.8 - 10.9#
High Moisture Content
14.1 - 14.3#

500,000

700,000

900,000

13.1

1-3.0

11.9

11.9

14.8

13.0

13.7

14.2

Table XXII.
ANALYSIS OF VARIANCE OF FREE FATTY ACID--END OF FOURTH RUN
Sum of Squares
Moisture Means
Treatment Means
Residual
Total

MWan
d.f. Square

4.20
1.57
1.51

1
3
3

7.28

7

F

4.20 9.34
.523 1.04
.503

f .35
10.1
9.28

It Is evident that the F test does not 3how any differ­
ence in treatment means or moisture means at the five percent
level of significance for the free fatty acid tests.

Here

again there seem to be no more profitable comparisons.
Analysis of the fifth respiration r u n .

The fifth res­

piration run v/as with two levels of moisture between 12.0 12.3 percent and 15.7 - 16.1 percent and treatments of 0,

80

500,000, 700,000, and 900,000 rep.
pare with those of run three.
shown in Table XXIII

The results should com­

These data for this run are

arid Figure 21.
Table XXIII.

RESULTS OF THE FIFTH RESPIRATION RUN
T1

Moisture e o n t . at
start (Wet basis)
COgmg/lOO Sample
gr D .M .
1st
2nd
Fr.fat.acid 10th
day mg KQH/lOOgm
D.M.

L

'■ "

0 re P

700, 000

500 , 0 0 0

16 .1

12.1

16 .0

12 .0

11.0
11.7

3 .6
2 .3

4.7
3.7

2.7
2.1

18.4

15.5

15.5

14.2

900, 000

15.0 12.3 15.7 12.1
2.9
2.1

2.9
1.7

1.7
1.7

1.1
1.9

15 .4 13.7 16 .7 16 .0

Table X X I V a .

Sum of Squares
Replication means
Treatment means
Moisture means
Interaction
Error
Total

d.f .

0.72
72.53
28.09
45 .79
2 .41

1
3
1
3
7

149 .54

15

H

.

b
o

j. _

o

ANALYSIS OF VARIANCE FOR COg PRODUCED

Mean
Square
.72
24 .18
28.09
15 .63
.344

DAY-- FIFTH RUN

F

*\95

0.05
1.55
1.80

5 .59
4.35
5.59

-/f Interaction mean square used as the denominator to determine
the F r a t i o ,
Since the interaction mean square was so much larger than
the error mean square, the interaction mean square was used
in the denominator to determine the F ratios.

Here again

80-i.

there were no significant differences in treatment means
nor moisture means.
. Analyses of variance were made for both the high mois­
ture treatments and the low moisture treatments to avoid
the effect of the large interaction.
Table XXIVb.
ANALYSIS OP VARIANCE FOR C02 PRODUCED ON 10th DAY--FIFTH RUN
HIGH MOISTURE ONLY
1

...

.

d.f .

S,S .

M .S .
38.7
.33

Replications
Treatments
Error

1
3
3

.15
116.16
1.08

Total

7

117.24

F
117.27

f .95
9.28

According to the F test there was a significant differ­
ence between treatment means at the five percent level of
Carbon dioxide
significance.
respired per 24hrs
Average of
0 rep treatment at high moisture 11.4
n
" 500,000
"
"
"
"
"
2.2
"
u 700,000
"
"
M
”
,T
2.5
" 900,000
"
"
tr
«t
'i
1. V
2( .33)
-

.57

Standard Error of a Mean Difference,

Comparing 0 rep treatment with 700,000 rep treatment.
11.4 - 2.5
= 15.81

t .57

81

Comparing 700,000 rep treatment with the 900,000 rep
which is the largest comparison that can be made above 0
treatment.
2.5 - 1.7
t -

=1.40
.57

t -

2.36 for seven degrees of freedom at the five
percent level of significance.

According to these comparisons there was at the five
percent level of significance a difference between 0 rep
treatment and the 500,000, 700,000, and 900,000 rep treat­
ments, but none between the 500,000, 700,000, and 900,000
rep treatments.

(The first comparison was made between those

that had the least difference and the second comparison wag
made between the 500,000, 700,000, and 900,000 rep treat­
ment that showed the greatest difference. )
Table XXIVc.
ANALYSIS OF VARIANCE FOR COg PRODUCED ON 10th DAY--FIFTH RUN
LOW MOISTURE ONLY

d .f .

S .S .

M.S .

F

p .95

1.40
1.51

9.88

Replications
Treatment s
Error

1
3
3

0 .66
2.14
1.41

0 .66
0.71
0.47

Total

7

4.21

0.60

81a

According to the P test at the five percent level
there is no significant difference between treatments at
low moisture.
Analysis of variance was carried out for the free
fatty acid tests.
Table XXV,
FREE PATTY ACID (mgKOH/lOOgrD .M .)--END OP FIFTH RUN

Sum of Squares
Moisture Means
Treatment Means
Residual
Total

d .f ,

5 .45
8.06
1.29

1
3
3

14.80

7

Mean
Square
5.45
2.69
.430

P

P .95

12.67
6 .25

10.1
9.28

There is clearly a difference in moisture means at the
five percent level of significance and nearly a difference
in treatment means .

Examination of Table XXV reveals that

at 500,000 and 700,000 rep there is a low point in the fat
acidity.

This can be observed also in Table XVII for the

third respiration run for high moisture wheat.

At the higher

doses (900,000 rep) the free fat acidity is increased.

A

82

t test to determine the difference between treatment means
of 0 treatment and 500,000 rep yields:
2 ( .430)
--------2

— ,635

The standard error of a mean
difference.

(14.2 -f 15.5)
- 14.8

at 500,000 rep

r 17.0

at 0 rep

2
(15 .5 + 18.5)

t

17.0 - 14.8
r -------------- - 3.31
.635

t t

3.18

at the 5.0 percent level of signifi­
cance for 3 degrees of freedom.

This shows a strong significant difference between 0
and 500,000 rep at high moisture content.

mg
Product ion
of
C02
per
100 g m .
of
dry matter
per 24 hrs

15 4

1st sample 15.7-16.1 moisture X
!2nd sample 15.1-16,1
M
^
1st sample 12.0-12.3 n
2nd sample 12.0-12.3 A
moisture
i
500,000

f
700,000

900,000

Treatment in reps
Fig. 21

Production of C02 vs. Treatment --Run Five

83

Summary of the Respiration Tests
1. At moisture levels ahove 15.0 percent there was a
significant difference between treatments at 0 and treat­
ments above 500,000 rep for the respiration tests.
2. There was not a great difference in effect upon
respiration at treatments below 500,000 rep.
3. The free fatty acid test was not a satisfactory
method of testing for changes due to treatment.
4. In some cases there was an actual increase in free
fatty acid with treatment, especially at the 900,000 rep
level of treatment,
Analysis of the Thermos Bottle Tests
The thermos bottle tests consisted of five runs of 20
days duration with an average room temperature of about 87
degrees Fahrenheit.

The thermos bottles were one pint in

size and were filled to the top and not stoppered.

A cali­

brated thermocouple was placed in the bottom of each bottle
and the temperatures read every other day.

The samples

placed in the bottles were a division of the same sample made
for the respiration run.

An exception to this was run five,

in which an attempt was made to duplicate the moisture per­
centages of the respiration run.

Actually the high moisture

level averaged 16.8 percent against about 16.0 percent for
the respiration run. The treatments were on the same level
as the corresponding respiration run.

84

Analysis of the thermos bottle test--run one.
XXVII

Table

lists the temperatures recorded for the thermos bottles

of run one.

The analysis of variance for the temperatures

is shown on Table XXVIII.

The analysis of variance was made

for two variables of classification of repeated measurements.
Table XXVII.
THERMOS BOTTLE TEMPERATURES DEGREES FAHRENHEIT--RUN ONE
Treat­

rep

Mois­
ture^
(Wet
ba sis )
start

0
0
130,000
130,000

16.6
12.2
16.9
11.9

78 87
76 .987
77.5 87
76 87

261,000
261,000
392,000
392,000

16.7
12 .05
16 .85
12.1

78
86
75
79

87 84 .587 87
87 84.5 87 87
86 .5 84 .587 87
86.5 84.5 86 .5 87

88

88

ment

Room
Temperature

Aver­
age
Tem­
pera­
17 19 20 ture

Day of Reading
1

3

5

9

u

13

85 87.5 87.25 87
85 87.5 86
86
85 .87.5 87
87
84.5 87 86
86

85

87

15

88 87
87 86
88 87
86 .586

87 88
86 87
87 88
86 .587

87.5 87

87

89 88
88 87
89.9 88
88 87

87 90
86 .589
87.5 90
86 88
90

87

89
87
89
87

87
87
88
86

86.4
85 .7
86 .5
85.4

88
86
87
86

86 .59
36 .6
86.2
85.8

187 87 87.3

Table XXVIII.
ANALYSIS OF VARIANCE THERMOS BOTTLE TEMPERATURES--RUN ONE

Sum of Squares

Mean
Square
d .f.

Treatment s
Moistures
Interact ion
Subtotal
Within groups

5 .80
1.04
8.64
15 .48
643.74

3
1
3
7
80

1.93
1.04
2 .88
2.21
8.05

Total

659.22

87

4.70

p
.177
.095

P .95
4.07
4.00

w Denominator is the pooled sum of interaction and within
group mean squares, as the interaction is not significant.

85

According to the P test at the five percent level of
significance, there is no differcence in treatment means or
moisture means.

However, there does appear to he a small

difference between the low moisture average temperatures and
the high moisture average temperatures, except for the
261,000 rep treatment when both average temperatures were
about the same.
The treatment at this level had little effect, which
was similar tc that of run one of the respiration tests*
Since the zero treatment, high-moisture average tem­
perature is not the highest average temperature, the thermos
bottles evidently were too small and aeration too inadequate
to produce the high temperatures necessary for a significant
difference.
The reason the room temperatures appear higher than the
thermocouple temperatures in the thermos bottles was that
the mercury thermometer was located at a higher elevation
in the room than the thermos bottles.

The room in which

the thermos bottles were kept tended to have a slightly high­
er

temperature near the ceiling. This would account for the

higher average temperature of the room thermometer in some
instances .
Analysis of the thermos bottle test--run t w o .

In run

two the treatments were increased to 1 x 10^, 2 x 10^, and
3 x 106 rep corresponding with those in the respiration

86

tests.

Table XXIX

lists the temperatures for this run.

As

in run one an analysis of variance was made for two variables
of classification of repeated measurements.

This is shown

in Table XXX.
Table XXIX.
THERMOS BOTTLE TEMPERATURES DEGREES FAHRENHEIT--RUN TWO

Treat­
ment
rep

Mois­
ture'^
(Wet
bas is ;
start 1

0
0

16.7
12.8
1 x 10° 16.7
1 x 106 12 .8
2
2
3
3

x
x
x
x

10®
106
106
106

16.5
12.8
16 .8
11.9

Room
Temperature

Day of Reading
3

7

5

9

11 13

15

19

20

87
86
86
86

87
86
86
86

87
86
86
86

87
86
86
86

87.5
86.5
86.5
87

88.6
86.
86.1
86.4

86
86
86
86

86
86
86
86

86.5
86.5
86.5
86.5

86
86.1
86.1
86.1

87

87.1

83
83
84
85

86
86
86
86 .5
86
86
87
86

84
83.5
84
84

86
86 .5
86 .5
86

87 .586 .5
86 87.5
86 87.5
86 88

86 .586 86
87 86 86
87 86 86
86 .586 86

87

87

87

87

88
87.5
87
88

90

88
87
87
87

Aver age
Tem­
perature

87 86 .586 .586

Table XXX
ANALYSIS OF 'VARIANCE THERMOS BOTTLE TEMPERATURES--RUN TWO
T"

- -

—

Sum of Squares

d •f .

Me an
Square

Treatments
Moistures
Interaction
Subtotal
Within group

0.9
0.1
2.2
3 .2
78.1

3
1
3
7
72

0.03
0.10
.73
.46
1.09

Total

81.3

79

1.03

F ”ratio

F #95

.0165
.055

2.74
3.98

* Denominator is the pooled sum of interaction and within
group sum of squares as the interaction is not significant.

87

According to the F test there is no significant differ­
ence in treatment means or moisture means at the five percent
level of significance.
In this experiment it was expected that there would be
a rise in temperature of the no treatment, high moisture
sample as there was a large production of carbon dioxide in
the respiration tests.

For this reason a t test was made to

determine the difference between no treatment, high moisture
and 1 x 10 G rep treatment, high moisture.
i 2 11.071)
-------10

r .463

t -

88.6
86 .1
----------.463

t

2.90

The standard error of a mean
difference.

-

=

: 5,4

for the 0.5 percent level of signifi­
cance for 72 degrees of freedom.

This very significant difference indicates that treat­
ments of 1,000,000 rep and above had a very strong effect
on temperature.

Tnis result was similar to that of the

respiration run .
Analysis of thermos bottle test--run three.

In test-

run three the treatments were lowered to 500,000, 700,000,
and 900,000 rep.

In run two the treatment at 1,000,000 rep

was very effective, while the treatment at 392,000 rep in
run one had no effect .

Between these two treatments a turn­

ing point should be found.

88

The results of run three are shown in Table XXXI.
No analysis of variance for temperatures was made (see Table
XXXI ), since there is practically no difference in average
temperatures.

Evidently at moistures below 16 percent very

little heat is produced.

Run two had been at higher mois­

tures and therefore a treatment of 106 rep had some effect.
In run three, shown below, all moistures were below 16.0
percent and there was little difference between samples.
Free fatty acid determinations were made of all sam­
ples, the x*esults of which are given in Table XXXII.

Ana­

lysis of variance was made of the free fatty acids in
Table XXXIII.
Table XXXI.
THERMOS BOTTLE TEMPERATURES DEGREES FAHRENHEIT--RUN THREE
Mois­
ture^
Treat­ (Wet
ment
basisT
rep
start

8

10

12

14

16 18

Aver­
age
Tem­
pera­
20 ture

87
87
87
87

85 .5 85 .8
85
85.7
85
85 .9
86
35 .7

Day of Reading
2

4

6

0
0
500,000
500,000

15 .65
11.3
15 .5
11.3

83
83
84
83

'86
86 87
86 .86 .5 86
37.5[86 .5 36
86
86 86

86
86
86
86

85 .5
85 .5
35,5
85.5

86
86
86
86

86
86
86
86

700,000
700,000
900,000
900,000

15 .5
11.7
15 .9
11.3

83
83
83
83

86
86
86
86

86
86
86
86

86
86
86
86

85
85
85
85

86
86
86
86

86 87 85
35.6
86 87 85
85.6
86 8 * 7 85 .5 85 .6
86 ,87 85.5 85 .7

37

1 i
87! 87 8 5
r
i

Room
Temperature

86
36
35 .5
86

.5
.5
.5
.5

I

34

87.5 86

86

87 87
.. i

i

86 .3

89

Table XXXII.
PRES FATTY ACID(mgKOH/lOOgrD.M.)TEST FOR THERMOS BOTTLE--RUN
THREE
Moisture??
We t Basis
at start

Treatment reps
0

500,000

700,000

900.000

11.3 - 11.7

13.0

13.0

20.2

13.1

15 .5 - 15 .9

17.8

16.0

14.2

15 .5

Table

XXXIII.

ANALYSIS OF VARIANCE FREE FATTY ACID(Mg.KOH/lOOgmD.M.)--RUN
THREE

Sum of the Squares

Mean
d.f. Square F ratio

Moisture Means
Treatment Means
Res idual

2.20
10.50
34.70

1
3
3

Total

47.40

7

2.20
3 .50
11.57

.190
.302

f .95
10.1
9 .28

According to the F test there is no difference in treat­
ment means or moisture means at the five percent level of
significance.
able

The results of this test were almost predict­

except for the sample at the treatment 700,000 rep, low

moisture.

The high value of 20.2 introduces the possibility

of a large error either in sampling, measuring,

or testing.

Except for this value the low moisture content wheat has low
values, and for high moisture content wheat the values are
lower for the treated samples than for the untreated.

90

Evidently there is a large error or errors somewhere that
will not permit us to find a meaningful difference.
Analysis of the thermos bottle test--run f o u r .

The

results of the thermocouple temperatures in the thermos bot­
tles can be 3een in Table XXXIV.

This run was made at an

even lower moisture percentage than run three, which was done
to obtain comparable runs with the respiration tests.

No

analysis of variances was made of the mean temperatures as,
one can see, there is practically no difference in mean
temperatures.
The results of the free fatty acid tests appear in
Table XXXV

and the analysis of variance in Table X X X V I .
Table XXXIV.

THERMOS BOTTLE TEMPERATURES DEGREES FAHRENHEIT--RUN FOUR

Treat­
ment
rep

Mois­
ture^
(Wet
bas is)
start

0
0
500,000
500,000

14.3
10.8
14.1
10.9

84
84
84
84

85
35
85.5
86

85 .5
35.5
85.5
85 .5

700,000
700,000
900,000
900,000

14 .2
10.9
14.3
10.8

85
85
85
86

86
86 .5
86.5
86 .5

35 .5
85 .5
85 .5
85 .5

Room
Temperature

D ay of Reading
2

4

10 12

14

16

85 .5
85 .5
85.5
85 .5

86
86
86
86

36
86
36
86

86 .5
86
85 .5
85 .5

37 .5
87.5
87.5
85

85 .5
85.5
85 .5
85 .5

86
86
86
86

86
86
86
86

85 .5 86 * 87.5 86.9
36
86
87.5 86.0
37
87.5 86.1
86
87
87
87.5 86.3

37

87 87

6

87 87.5 87

Aver­
age
Tem­
pera18 ture

8

36.5 87

88.5
88.5
87.5
88

87

86.0
86.0
85.9
85.8

87

91

Table XXXV.
FREE FATTY ACI D {mgKOH/lOOgrD.M.) FOR THERMOS BOTTLE--RUN FOUR

Moisture^
Wet basis
at start

Treatment reps
0

500,000

700,000

900,000

10.8 - 10.S

17.7

17.2

16.0

16.7

14.1 - 14.3

17.7

17.7

16.5

17.2

Table XXXVI .
ANALYSIS OF VARIAN CE FREE FATTY ACID(MgKOH/lOOgmD.M.)--RUN
FOUR

Sum of Squa res

Mean
d.f. Square

Moisture Means
Treatment Means
Residual

.28
2.45
.10

1
3
3

Total

2 .83

7

28
816
033

F ratio

P gg

8.48
24.72

10.1
9.28

According to the F test at the five percent level of
significance there is a difference in treatment means.

A t

test was made between the high moisture treatment at 500,000
rep and 700,000 rep.
The standard error of a mean difference is:
2 ( .0333)
— ------*

V 1
t

-

“ .257
17.7 - 16.5
---------.257
4.18

r 4.67

at the 2.5 percent level of s i g n i ­
ficance for three degrees of freedom.

92

This shows a strong significant difference.
Analysis of the thermo3 bottle test--run five.

Run

five was carried out at higher moisture percentages than any
previous run.

Also the wheat was tested for moisture on a

Tag-Heppenstall moisture meter.

This sample had to he dried

slightly to bring it below 17 percent during preparation of
the sample, and it is believed most of this drying occurred
on the surface.

A Tag-Heppenstall moisture meter tends to

'read’ the surface moisture, and therefore this sample may
have been even slightly higher in moisture than indicated.
The results of the thermos bottle temperatures are
shown in Table XXXVII.
Table XXXVII.
THERMOS BOTTLE TEMPERATURES DEGREES FAHRENHEIT--RUN FIVE

Treatment
rep

Moisture/£
(Wet ____________
basis )
6
2 4
start

0
0
500,000
500,000

16 .8*
io.8':;
16 .8"
10.9*

85
85
85
86

86 .5
86.5]
86 .5
86.5

700,000
700,000
900,000
900,000

16.8*
10. 9~
16.8*
10.8"

86
86
86
86

86 .£85 .5 86
87
86 .5 86 .a85.5 86
87 86 .586
87
87 85 .586
87

Room
Temperature

18

Day of Reading_______
8

10 12

86 85.5 87
86 85 .686
86 85 86
86. £85 .586

87 87.5 87

16

Average
Tempurature

14

88
87
87
87

87.5
87
87.5
87

87.5
86
86 .5
86 .5

88.5
87.5
87.5
87

86.8
86 .3
86 .4
86 .4

87
87 .5
87 .5
86

87
87
87.5
87.5

86 .5
86 .5
87 .5
87

88
87
88.5
87.5

86 .5
86 .5
86 .9
86.6

87

87

P7 87
j
._.._j—

86 .5 87

# Taken by Tag-Heppenstall Moisture Meter .

1

93

No analysis of variance was made of the mean temperatures
as practically no difference in temperatures occurred.
The results of the free fatty acid determinations are
given in Table XXXVIII

and the analysis variance on Table

XXXIX.
Table XXXVIII.
FREE FATTY ACID(mgKOH/lOOgrD.M.)FOR THERMOS BOTTLE--RUN FIVE

Moisture/^
(Wet basis)
at start

Treatment Rep
0

500,000

700,000

900.000

12.0 - 12.3

16 .0

16.6

16 .0

16.0

15.7 - 16.1

26.0

24.2

19.6

21.9

Table XXXIX
ANALYSIS OF VARIANCE FREE FATTY ACID(mgKOH/lOOgmD.M . )_ -RUN

Sum of Squares
Moisture Means
Treatment Means
Residual
Total

91.80
12.70
10.76

1
3
3

115.26

7

According to the F tost
between the moisture means.
the highest
Let us

Mean
d.f. Square
91.8
4.23
3 .58

F ratio

F .95

25.64
1.18

10.1.
9 .28

fiv:

there is a significant difference
This might be expected as it had

moisture average of any run so far.
compare high moisture, 0 treatment with high mois­

ture, 700,000 rep treatment.

94

The standard error cf a mean difference is:
\[2 (3 .58 )

\|
t

=

t r

= 2.68

26 - 19.6
---------2.68
2.35

r 2.39

at the 10.0 percent level of signifi­
cance for three degrees of freedom.

This shows again that there is a low point in the free
fatty acid determination .at 700,000 rep, high moisture.
Summary of the Thermos Bottle Tests
1. A pint thermos bottle sample apparently is too small
to effect a rise in temperature.

In only one run was there

a significant difference between a treatment and no treatment
and this was not very large . Evidently to achieve results
similar* to a grain bin, air should be piped down to the bot­
tom of the bottle .

Ho doubt an aerobic action was taking

place which was not conducive to heat production.
2. In all tests made, the free fatty acid test In the
high moisture level showed lowest at 700,000 rep treatment
with an Increase in the free fatty acid test at 900,000 rep
treatment.

The general trend was a decrease in fat acidity

from no treatment to the 700,000 rep treatment and then an
increase in fat acidity.

This increase in fat acidity at the

900,000 rep level was also noticeable in the respiration
tests .

95

Comprehensive Tests
The purpose of these tests was to find out how samples
of wheat treated at zero and 900,000 rep reacted to milling
and baking tests.

There were eight samples, four of which

had no treatment and four the 900,000 rep treatment.

The

900,000 rep treatment was selected as it was the one that
was most successful in reducing the respiration to the lowest
level.

The moisture levels in the test were 12.2 - 12.2 per­

cent, 14.0 - 14.1 percent, 14.6 - 14.7 percent, and 15.6 15.7 percent.

It had been intended that moisture percentages

at the 14.6 - 14.7 percent and 15.6 - 15.7 percent levels
should be one percent higher.
The respiration part of the test was run for ten days
with an average passage of air over the samples of 16.0 mil­
liliters per gram of dry matter.
was slightly lower than

This rate of air passage

that of the respiration tests.

The air exchange was obtained by making five air

changes

of 3,8 liters 9t equal intervals of time every 24 hours.
The average ambient temperature was 87 degrees Fahrenheit.
A complete set of milling and baking tests was made
for each of these samples.
shown on Tables XL

The results of these tests are

and XLI .

The milling and baking tests

were made by the International Milling Company.

96

Table XL.
MILLING DATA
^Moisture at
start of test 12 .2
Treatment rep

0

12 •2
9xl05

^DWMoisture** 10,4
% WT R M o istur e 14.8
% Extraction 70.4
% Bran
21.2
% Short s
6 .0
Milling time* 5 f ,01”
% Flour
moisture
13.1
z^Flour ash
at 14
.415
$Flour prot .
at 14 13.55
Mgs .maltose
at 14 157
FFA (mg.KOH/
lOOgm at0/£mt)23.9
Odor of flour
water paste N o r m .

14.1
0

14.0
1
9xl05

14.7
0

14.6
1
9xl05

15 .7
0

15.6
9xl05

13.5
14.8
70.8
21.6
6.4
4,47

13.2
14.9
70.3
21.9
6.4
4,39

13.0 13.0

13.0 13.0 13.1

13.3

.458 .472

.452 .432 .458

.434

10.5
14.9
71.7
21.3
6 .5
10,13

11.6
14.8
70.5
32 .0
5.9
4,38

12.9
.471

11.9
15.6
70.7
21.5
6.0
4,51

13.72 13.70 13.45

12.1
14 .7
71.5
21.7
6.3
5,00

12 .0
15 .0
70.8
21.7
6.3
4,51

13.8513.8513.75 13.75
131

188

160

192

160

23.8

24.5

25 .1

22.6 21.S 21.3

V-Bad Norm. V-Bad

N orm .Bad

157

178
22.6

N o r m . Bad

* IP, 2P , and 3P/1000 gram samples, 4 P , 5 P , 6 P , 7 P , and 8P/
1100 grams.
Before milling.
D.W.Moisture means percent moisture of the dry weight of the
the wheat prior to tempering before milling.
%WFR Moisture means percent of moisture of the dry weight
after tempering’and just prior to milling.
% "Extraction means percent of total flour obtained from total
wheat.
Mgs. Maltose at 14 means milligrams of maltose at 14,0% mois­
ture of 100 grams of dry matter.
PPA (mg.KOH/lOOgm at O^mt) means free fatty acid of 100 grams
of dry matter.

97

Table X L I .
BAKING DATA

^Moisture at
start of test 12 .2
Treatment rep

0

Absorption
61 $
Mixing time
61
Dough
handling Good
Avg.loaf
ol .3040
Total score
(max.41)58.0
OK
Odor
Taste
OK
Baking quality VG-

12.2
9xl05

14.1 14.0
0

9xl05

14.7 14.6 15.7
0

60$
7J'
Good.
SI .soft Good S I .soft
3000
3075 2890 3025
60$
7'

37.0
Mild
Mild
Good

61$
7'

38.0
Mild
OK
VG-

62$
6i'

34.5 38.0
Strong OK
VStrongOK
Pair
VG-

9xl05
60$
6!
Good

0
61'fo
9T

15.6
9xl05
62%
8r

Good
3975 3115

Good
2925

37 .0 38 .0
Mild OK
Mild OK
Good VG-

37.0
Mild
Strong
Good

Notes made by those conducting the bake test and the
scoring of the baked loaves were as follows:
"The odor might not be strong enough to be objection­
able to a customer, but the taste, designated as mild, would
be objectionable . The odor and taste were like burned feath"When the flour was checked for odor by making a flour hot water paste, the odor of those samples designated as
very bad was described as similar to that of burned hair."
"Absorption in the baking test means percent of water
needed at 14.0 percent moisture (dry basis) to obtain a
dough of satisfactory and optimum consistency."

93

Analysis of Milling and Baking T e s t s .

Table XL

shows

that there is not a great difference in percentage of mois­
ture of the samples before the milling tests are made as all
samples were purposely not stoppered or sealed after going
through the ten-day respiration run.

However, it can be seen

that there is a slightly higher moisture for those samples
that were higher in moisture at the start of the test.

Evi­

dently, they had not reached equilibrium.
Table XLI

discloses that there is an unusually long

milling time for the 12.0 percent, 900,000 rep treatment.
This time is more than twice the average, and there seems no
reason why this should be so.
The test for milligrams of maltose at 14 percent mois­
ture seems to indicate a difference in treatments. This is
indicated in an analysis of variance test in Table XLIII.
Table X L I I .
TEST FOR MILLIGRAMS OF MALTOSE AT 14# MOISTURE
__________ Moisture (Wet basis) at start of test
Treatment___ 12.2 - 12.2# 14.0-14.1#

14.6-14.7# 15.6-15.7#

0

157

160

160

157

900,000

188

192

181

178

99

Table XLIII.
ANALYSIS OP VARIANCE FOR M O S . OP MALTOSE AT 14# MOISTURE

Sum of Squares

d.f.

.78
11.29
3.04

3
1
3

15.11

7

Moisture Means
Treatment Means
Residual
Total

Mean
Square
.26
11.29
1.01

P
.257
11.18

F .95
9.28
10.1

According to the F test at the five percent level of
significance there Is a difference in treatment means for
milligrams of maltose at 14 percent moisture. This treatment
effect is not gre^fc, but significant.
The free fatty acid test showed a difference in moisture
means, as shown in Tables XLIV

and XLV .

Table XLIV.
FREE FATTY ACID (mgKOH/gmD .M.) FOR COMPREHENSIVE TESTS

Moisture (Wet basis) at start of test

Treatment
reo

12 .2 - 12.2# 14.0 -14 .1# 14. 6 -14.7# 15.6 -15.7#

0

23.9

24.5

22.6

21.3

900,000

23.8

25.1

21.9

22.6

100

Table XLV.
ANALYSIS OF VARIANCE, FREE FATTY ACID (mgKOH/lOOgmD .M.)
COMPREHENSIVE TEST

Sum of Squares

Mean
d.f. Square

Moisture Means
Treatment Means
Residual

10.89
.15
1.14

3
1
3

Total

12.18

7

3.63
.15
.38

F

F 95

9.55
.0395

9.28
10.1

The F test reveals a difference in moisture means at the
five percent level of significance.
The average loaf volume was about the same except for
the 14.6 - 14.V percent moisture, 900,000 rep treatment.
There is no accounting for this unusually high loaf volume
since the other treatments averaged slightly lower than the
non-treated samples.
The mixing time increased a small amount as the mois­
ture -increased.

Treatment seemed to have no definite effect.

This pan be seen best in Table XLVI.
Table XLVI.
MIXING TIME
Moisture (Wet basis) at start of test ■
Treatment
rep

12 .2 -12 ,3%

14.0 -14.1/o 14.6 -14.7/5 15.6 -15 .7i

0

6T

7'

7i ’

8'

900,000

7’

6*'

6'

8'

101

The total 3core averaged 37.0 for the treated samples
and 38.0 for the non-treated samples with the' exception of
34.5 for the low moisture (12.2 percent), 900,000 rep treat­
ment.

For some reason this scored very low.
Baking quality was very good minus on the non-treated

samples and good on the treated samples with the exception
of the treated 14.0 percent moisture sample which was graded
fair .
Summary of the milling and baking tests .

The milligram

of maltose at 14 percent moisture seemed to be influenced by
the 900,000 rep treatment.

Other effects were noticed such

as total score, average loaf volume, and dough handling, but
none were significant.
A review of all the results of the milling and baking
tests does not show a great deal of difference in milling
and baking quality, except for the odor, for both the milling
and baking tests and the taste for the baking test.

The taste

was designated as mild; however, it would be objectionable to
a consumer,

102

SUMMARY
Treatments of 500,000 rep and above reduced the respi­
ration rate of wheat between 15.0 - 16.8 percent moisture
(wet basis) in the ten-day respiration test at 86 degrees
Fahrenheit.

In most cases it was found that for treatments

of 500,000 rep there was little difference in resoiration
between high-moisture wheat (15.0 - 16.8 percent; and lowmoisture wheat (10.8 - 12.8 percent).

This indicated that

treatments of 500,000 rep reduced the activity of molds to
a low level.
Treatments of 392,000 rep and below had no effect upon
the respiration rate.
The free fatty acid test was not a satisfactory index
of deterioration.

As a rule, for the respiration tests for

high-moisture content wheat (15.0 - 16.8 percent) there was
a reduction in free fatty acid at the 500,000 and 700,000 rep
treatment and an actual increase again at the 900,000 rep
treatment.
A pint thermos bottle was too small a sample to effect
a rise in temperature due to the heat production of wheat.
In only one run wa3 there a significant difference in tem­
perature between a treatment and no treatment, and this
difference was not very large.

Evidently, to achieve

results similar to a grain bin, air should be piped

103

down to the bottom of the bottle.

No doubt aerobic action

was taking place which was not conducive to heat production.
In the thermos bottle tests there was a decrease in
free fatty acid at the high moisture level 500,000 rep and
700,000 rep treatments with an increase again at the 900,000
rep treatment.

This was similar to the results in the res­

piration tests .
The most significant result of the comprehensive milling
and baking tests was the burned odor and taste.

While this

was not great, it would be definitely noticed by a consumer.
49
In the work of Wiant
it was found that dosages of 50,000
rep and above had a burned taste and odor.

To avoid this

burned taste and odor dosages must be lower than 50,000 rep,
at least through the bread-making part of the wheat. According

4B
to the work of ThompsonJ the heating of stored wheat

Is due to a fungi next to and inside the epidermis of the
wheat.

If this is true, then it is not necessary to give

such penetrating dosages to wheat nor at such high dosages
throughout.

Perhaps a pass on either side may be adequate

if of the right dosage and penetration.

Also, some way may be

found to roll wheat while under the beam to give an even pen­
etration

through the epidermis.

Finally, there were some minor milling and baking
effects.

The milligrams of maltose at 14.0 percent moisture

seemed to be increased at the 900,000 rep treatment.

Other

effects noticed were the slight decrease in total score and

average loaf volume at higher levels of treatments.
were significant.

None

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