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OTATO PROTEIN . _ j
A. VARIETY AND ENVIRONMENT AND
B. AIR SEPARATION OF THE DRIED FLOUR
Thesis for the Degree of M. S.
MICHIGAN STATE UNIVERSITY .
. ORAL!) M. PEARE’
1973

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ABSTRACT

POTATO PROTEIN AS AFFECTED BY: A. VARIETY
AND ENVIRONMENT AND B. AIR SEPARATION
OF THE DRIED FLOUR

BY

Ronald M. Peare

Sixteen potato cultivars grown in 10 different
states were analyzed for total protein, net usable protein,
"available" methionine and protein quality. A micro-
biological method utilizing Streptococcus zymogenes was used
to estimate "available" methionine content and protein
quality. Variety, location of growth and their interaction
was found to contribute significantly to the total variabi-
lity. Environmental data for each location could not be
related to location mean differences in any variable.

"Available" methionine (mg met/l6 mg N) was
positively correlated with biological value (r = .37) while
a negative correlation existed between BV and total protein
(r = -.28). No apparent relationship existed between
"available" methionine and total protein.

A factor indicative of the amino acid balance of
the total protein minus the contribution due to the con-

tained "available" methionine was found. This factor,

Ronald M. Pearo

termed "relative protein quality" was negatively correlated
with "available" methionine (r = -.77) and total protein
(r = -.26). This in combination with "available" methionine
content explained differences in BV to a greater extent than
either one considered individually. Selection criteria for
improved protein quality as influenced by the environment is
discussed.

Air classification of potato flour was investigated.
A protein concentrate flour derived from whole flour,
representing 30% of the initial dry matter and containing
33% protein was obtained. Rat and micro-biological evalu—
ation of the concentrate and whole flour (of one variety)
showed no differences in quality. Based on these assays,
the protein quality of the potato variety studied was 75%
as effective as casein.

The importance and potential of micro-biological
assay and air-classification in relation to the potato

industry is discussed.

POTATO PROTEIN AS AFFECTED BY: A. VARIETY
AND ENVIRONMENT AND B. AIR SEPARATION

OF THE DRIED FLOUR

BY

Ronald M. Peare

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Crop and Soil Sciences

1973

.07
:M ,i

ACKNOWLEDGMENTS

a.
“I" r
r?’

The author expresses his appreciation and thanks to
Dr. N. R. Thompson for his interest, advice and instruction
during my graduate study.

My gratitude goes to Drs. O. Mickelsen, D. Penner,
S. Wellso, and C. Cress for their time, advice, and labo-
ratory facilities essential for this study.

For his advice and assistance, a special thanks is
extended to Robert Luescher.

The author also expresses thanks to Dr. C. M.
Harrison for his help in the revision of the draft.

I would like to thank Mr. Dick Kitchen for his help

with technical aspects of this study.

ii

TABLE OF CONTENTS

Page
LIST OF TABLES . . . . . . . . . . . . . V
LIST OF FIGURES. . . . . . . . . . . . . Vii
Chapter
INTRODUCTION 0 O O 0 o 0 O o o o o o o o 1
REVI EW OF LI TE RATURE O O O O O O O O O O O 4
Content and composition of nitrogenous substances. 4
Nutritive value of the nitrogen substances . . . 5
The effect of environment on nitrogen content and
composition. . . . . . . 7
Nitrogen content as related to stage of growth. . 8
Effects of water. . . . . . . . 9
Effects of soil properties and fertilizer . . . 9
Effects of storage . . . . . . . . . . . 13
Effects of variety and location on nitrogen
content . . . . . . . . . . . . . . 14

PART I. THE EFFECTS OF VARIETY AND LOCATION AND THEIR
INTERACTION ON PROTEIN QUANTITY AND QUALITY

INTRODUCTION. . . . . . . . . . . . . . 19
MATERIALS AND METHODS. . . . . . . . . . . 20
Determination of total protein . . . . . . . 21
Determination of "available" methionine . . . . 22
Determination of biological value of potato
protein . . . . . . . . . . . . . . 23
Discussion of S. zymogenes . . . . . . . . 24
Determination of net protein. . . . . . . 25

Determination of the relative quality of potato
protein minus the effects of "available"
methionine . . . . . . . . . . . . . 25

iii

Chapter Page

RESULTS AND DISCUSSION . . . . . . . . . . . 27

SUMMARY . . . . . . . . . . . . . . . . 37
PART II. PROTEIN QUALITY OF WHOLE POTATO FLOUR

AND AIR CLASSIFIED FRACTIONS AS MEASURED BY
RAT AND MICRO-BIOLOGICAL ASSAY

INTRODUCTION . . . . . . . . . . . . . . 38
MATERIALS AND METHODS . . . . . . . . . . . 39
Preparation of whole flour . . . . . . . . . 39
Preparation of concentrate flour . . . . . . . 39
Preparation of diets . . . . . . . . . . . 40
Determination of protein quality . . . . . . . 42

RESULTS AND DISCUSSION . . . . . . . . . . . 44

SUMMARY . . . . . . . . . . . . . . . . 48
LITERATURE CITED . . . . . . . . . . . . . 49
APPENDICES
Appendix

1. Environmental Data . . . . . . . . . . S3

2. Total Protein, "Available" Methionine, Biological
Value, Relative Protein Quality and Total Dry
Matter Data of 16 Varieties Grown in 10
Locations in 1971 . . . . . . . . . . 54

3. Total Proetin, "Available" methionine, Biological
Value, Relative Protein Quality and Total Dry
Matter Data of 8 Varieties in 4 Replications
Grown in Michigan in 1972 . . . . . . . 61

4. Analysis of Variance for Available Methionine,
Relative Protein Quality, Biological Value,
Total Protein and Total Dry Matter . . . . 62

5. Amounts of Added Components Per 1 kg of Potato
and Casein Diets . . . . . . . . . . 64

6. Protein Consumption, Weight Gain, NIB, and
Percent Body Protein Data of Rat Assay . . . 65

iv

Table

1.

LIST OF TABLES

Influence of increasing N rates on total
solids, total protein and non—protein
nitrogen . . . . . . . . . . . . .

Effect of variety on nitrogen content and
composition . . . . . . . . . . . .

Effects of variety and location on dry matter,
starch and protein content . . . . . . .

Percent of total variance in methionine, total
protein, and free N/total N contributed by
years, locations, varieties and their
interactions. . . . . . . . . . . .

Effects of variety, location and year on dry
matter, starch and protein content . . . .

Composition of Rural potatoes as affected by
cultural practices. . . . . . . . . .

Expected mean squares, their degrees of freedom
and F-ratios in the analysis of variance . .

Percent contribution by variance components to
the total variability in "available" methio-
nine, total protein, total dry matter, BV and
relative protein quality. . . . . . . .

Correlations among "available" methionine, total
protein (dry basis), total solids, BV, relative
protein quality, total protein (fresh basis),
"available” methionine/g dry matter and
available methionine/g fresh weight (data from
16 varieties grown in 10 locations . . . .

Page

12

14

15

16

17

18

22

28

30

Table Page

10. Mean value of varieties and locations for
"available" methionine, relative protein
quality, BV, total protein (dry basis),
calculated net protein content and
theoretical net protein content . . . . . 32

11. Composition of a 1 kg portion of whole potato
flour and air-classified fractions derived

from it . . . . . . . . . . . . . 40
12. Composition of casein, whole, and high protein

concentrate potato flours . . . . . . . 42
13. Means and ranges of rat responses as influenced

by casein and potato diets. . . . . . . 44
14. Correlations among PER, NIB, protein consumed

and weight gain . . . . . . . . . . 45
15. Micro-organism growth and rat responses on

potato diets as a percent of casein. . . . 45

vi

LIST OF FIGURES

Figure Page
1. Influence of available methionine and relative

protein quality on BV (data from 16 varieties
grown in 10 locations) . . . . . . . . 31

vii

INTRODUCTION

It is now recognized that in meeting world food
demands, emphasis must be placed on increased crop pro-
duction and yield, paralleled by increases in protein
content and quality. The alleviation of food shortages
and/or protein malnutrition by novel proteins, synthetic
foods, amino acid supplementation and new crop introductions
have been and will be of importance. However, due to the
complexities of distribution, industrialization, governments
and cultural backgrounds, progress in this area is inhibited.

Though not exempt from deficiencies, the permanent
improvement of quantity and quality through the genetic
manipulation of crops, in combination with good cultural
practices, more closely approach the principles of "putting
the food where the mouths are" and maintaining self-
sufficiency.

Grown everywhere in the world where temperate
climatic conditions exist, the potato has been a reliable
food source for man and animal. Generally regarded as the
"poor man's food," the nutritive value and potential of the

potato in contributing to world food demands is often

overlooked. Considered to be a good source of carbohydrate,
the potato also contains protein ranging from 10% to 17% on
a dry basis. Relative to other crop proteins Kuppuswamy

(22 31., 1958) reported net protein utilization values of

70 for the potato, 60 for wheat, and 50 for corn. In
relation to other crops the potato also ranks high in terms
of protein yield per unit area of land.

Methionine is the first amino acid which limits the
quality of potato protein. Feeding potato diets to voles,
Rios (1969) reported increased protein efficiency ratios
when diets were supplemented with methionine. Kies and Fox
(1972) found mean nitrogen balances of human subjects
receiving a potato diet alone or supplemented with methio-
nine to be -1.18 and -.27g N per day respectively.
Analyzing 16 cultivars micro-biologically, Luescher (1972)
found "available” methionine contents to be positively
correlated with protein quality.

Luescher (1971) found that genetic variability in
"available" methionine does exist and later (1972) reported
heritability estimates for this trait to range from 79% to
100%.

In a breeding program, information regarding the
effects of the environment on the trait under study is of
prime importance. Since the phenotypic variance of a trait
is composed of genetic and environmental variance, the

identification and removal of environmental variances, (by

sampling increased numbers of localities and/or years) will
provide a better estimate of the true genotypic variance.

To facilitate improvement of the potato, relation-
ships among and variability of protein content, protein
quality and "available" methionine as influenced by variety,
location and variety-location interaction were studied.

A preliminary study concerning the quality of a
high protein by-product of the potato industry was con-
ducted. Information concerning the comparability of micro-
biological and rat evaluation of this material was also

obtained.

REVIEW OF LITERATURE

Content and composition of nitrogenous substances

The potato in its fresh state has an average of 2%
crude protein, and may range from 10-17% on a dry basis. In
identifying the nitrogenous components of the potato, Chick
and Slack (1949) and Neuberger and Sanger (1942) found that
of the total N of the potato, 89-93% can be extracted with
a weak salt solution. Heat coagulation of this extract
resulted in precipitation of the protein "tuberin" which
accounted for 30-60% of the total soluble N. It was
composed of two proteins, one being globulin in nature,
retaining the name of tuberin, and the other tuberinin,
having characteristics of albumin, in a ratio of 70/30
respectively. Differences in the content of the sulfur
amino acids in tuberin from different genotypes were
reported by Luescher (1972).

The non-protein nitrogen, accounting for 40-70% of
the soluble nitrogen, is composed of 20% free amino acids,
40% amides, and 40% basic nitrogen, these values also
being subject to variation. Though the free amino acids

contribute only 8-14% to the total amino acid pool, Mulder

and Bakima (1956) found that free valine, methionine,
phenylalanine, and tryptophane may contribute considerably
to the total. Luescher (1972) found that 18% to 57% of the
total methionine was composed of free methionine.

The insoluble N accounting for 7-11% of the total N
has been found to consist largely of protein and asparagixe.
The high nitrogen content of the peel and outer cortex is
due to this fraction, while an increasing concentration
gradient of N from the vascular ring to the center is due
to soluble nitrogen present in the cell sap (Neuberger and

Sanger, 1942).

Nutritive value of the nitrogen substances

A 100 gram portion of whole raw potato contains
approximately 20.2 g total solids consisting of 17.1 g
carbohydrate, 2.1 g protein, .5 g fiber, .4 g salts and
vitamins and .1 g fat. Approximately 76 calories are
derived from this portion, 11% being protein calories.
These values vary, depending on the variety and method of
cooking (Watt and Merrill, 1963; Goldthwaite, 1925).

Quality improvement of the potato protein would add
to this very adequate food. Evidence strongly points out
that methionine is the amino acid which limits the biologi-
cal value of the potato protein (Williams, 1959). Kies and
Fox (1972) found mean nitrogen balances of human subjects
receiving a potato diet alone or plus methionine, phentla-

lanine, leucine, or a combination of these amino acids to

be -1.18, -.27, -.91, -.83, and -.30 g nitrogen per day
respectively. No differences were found in the digestibi—
lity of the potato protein as a result of amino acid
supplementation.

Studying the amino acid content of six strains of
potatoes, Rios (1969) found that of all the essential amino
acids, methionine had the lowest chemical score (as com-
pared to whole egg). These values ranged from 19-31 for
the varieties studied. Potato diets fed to voles resulted
in significantly higher protein efficiency ratios for all
varieties when supplemented with methionine. These high PER
values were associated with a greater digestibility and
utilization of the supplemented protein. Food intake was
similar in both cases. Finding varietal responses both
with and without supplementation, Rios concluded that those
varieties giving high PER values were in better amino acid
balance than other varieties. No relationship existed
between nitrogen content and its ability to support growth.
This was found to be true in the case of peas also (Bajaj
gt 31., 1971).

Luescher (1972) assessed the protein quality of 16
potato selections by measurement of the relative growth of
micro-organisms. Significant and positive relationships
existed between organism growth and methionine contents
(r = .60). Also, increases in nitrogen content (dry basis)
were positively correlated (r = .63) with non protein

nitrogen (as a percent of the total nitrogen) and negatively

correlated (r = -.41) with organism growth. In the same
study he found the heritability of available methionine to
range from 79% to 94%.

Factors other than the relative proportions of
protein N and NPN seem to influence the nutritive value of
the potato as indicated by Chick and Slack (1949).
Separating the protein and NPN from the soluble nitrogen,
they found that growth of weanling rats could be supported
by feeding the protein fraction alone, but not when the NPN
fraction was fed alone. However when fed a diet consisting
of unaltered soluble N which contained both the protein and
NPN fractions, rats gained weight to the same extent as
those whose diet contained the same content of nitrogen
from the protein alone. Protein efficiency ratio values
for the protein diet and the total soluble N diet were 1.54
and 1.52 respectively. The fact that the total soluble N
is digested to a greater extent than the protein N may in
part explain this occurrence.

In this same study, potatoes fed without the
periderm and outer cortex resulted in higher food intakes,
N digestibility and weight increases than when fed whole.
This is of interest since the major portion of the insoluble

N is contained in the periderm and outer cortex.

The effect of environment on nitrogen content and

composition

The content of dry matter in the tuber as well as

the relative amounts of the constituents in the dry matter

are subject to varietal and environmental influences.
Starch normally constitutes 60-80% of the dry matter, while
nitroqen, sugars, fat, fiber, and ash account for the
remainder. In many cases, the amounts of these latter
components have been found to be so consistent that the
percentage of starch has been calculated by subtracting a
constant from the percentage of dry matter present (Burton,
1966). Marcher (quoted from Burton, 1966) found a constant
of 5.8 to give an approximation of starch while Goldthwaite
(1925) found this value to be 6.7 for irrigated Coloradc
potatoes. Values obtained by other workers for particular
lots of potatoes ranged from 2.3-11.

Heinze (1955) found an inverse relationship between
dry matter and the proportion of nitrogen in the dry matter
(n = -.69). Similarly, Cobb (1935) found values which
ranged from .321% N in fresh tubers containing 22% dry
matter to .332% N in tubers containing 19% dry matter.
Thus, on a fresh weight basis, N content becomes more

similar.

Nitrogen content as related to stage of growth

Studying variations in N content during growth of
one variety, Fagen (1925) found that potatoes planted in
April and sampled in June had a dry matter content of 17.4%
and gradually increased to 22.2% in October. N expressed
as a percent of the dry weight and protein N as a percent of

the total N decreased from 1.49% and 46% in June to 1.06%

and 50% in August and again increased 1.35% and 57% in
October. Similar results were obtained for the next year.
In this case, immature tubers contained more N on a dry
basis than mature tubers. On a fresh basis however the
highest total N and protein N contents were found in mature
tubers. De and Singh (1959) reported similar results. The
variety studied decreased in N content from 2.17% at 47 days
after planting to 1.19% after 99 days.

Willaman and West (1922) reported that early

varieties had a higher nitrogen content than later varieties.

Effects of water

Growing the same varieties in both irrigated and
non-irrigated plots, Metzger (35 31., 1937) found that non-
irrigated plots had 8% less dry matter, 10% less starch, 2%
less fiber, 7% more ash and subsequently 13% more N than
irrigated plots. Similarly, Goldthwaite (1923) found that
dryland potatoes contained 15% more N and 10% less starch
than irrigated potatoes. No marked difference was noted in

dry matter content.

Effects of soil properties and fertilizer

The composition of potatoes as affected by ferti-
lizer applications has been a subject of extensive study.
The direct affect of applied fertilizer may be obscured by
variables such as previous cropping history, soil type and
its nutrient status, weather conditions, variety, and

numerous interactions. Schippers (1968) found dry matter

10

content of the four varieties studied to be inversely
related to increasing K rates when applied in the form of
sulfate. Dunn and Rost (1948) found lower dry matter
contents in tubers grown in KCL plots than in tubers grown
in K2804 plots. Increasing rates of KCL were associated
with increased water contents.

The same authors demonstrated that responses to P
and K, in terms of dry matter and N contents, are variable
in nature and influenced by chemical and physical properties
of the soil. Several varieties grown on a "potentially"
high or low yield soil, treated with identical rates of P
and K alone and in combination were compared to those plots
receiving no fertilizer. P applied to the heavy soils
decreased the percentage N on a per tuber basis but in-
creased total N accumulation (unit area basis) as a result
of an increase in dry matter content (per tuber basis). K
on the other hand decreased dry matter and N. P and K in
combination decreased dry matter and N content but increased
N accumulation as a result of increased dry matter pro-
duction. It was concluded that initially these soils
contained K at sufficient levels.

P and K applied alone on the low yield soils had no
effect on dry matter content, decreased N content, and
increased N accumulation, the latter being a result of an
increase in dry matter production. P and K in combination

decreased dry matter and N content but increased N

11

accumulation for the same reason as above. It was concluded
that these soils were deficient in P and K.

Average values for the heavy soil were 20.7% dry
matter content, 11.1% crude protein content, and 346 lb
crude protein/acre while for the light soil these values
were 22.3%, 9.8%, and 279 1b respectively. N content as a
percent of the dry matter tended to be higher in all check
plots. This agrees with Mulder and Bakima (1956) in that P
and K generally decrease total N on a dry weight basis.

In contrast to the effects of P and K, increasing
nitrogen fertilization tends to increase N content on a dry
basis. This may be due to a decreased dry matter content
and/or increased accumulation of N in the tuber. De and
Singh (1959) reported N contents of the variety studied to
increase with N fertilization, average values being 1.04%,
1.19%, 1.09%, and 1.18% at 0, 75, 150, and 225 1b N/acre.
Highest yields, on a fresh basis, were found at the 75 lb
rate. Higher rates resulted in decreased yields, more
vigorous top growth, delayed tuber initation and tuber rot.
Murphy and Goven (1959) found that over a period of 13 years
tubers of three varieties treated with 60 lb N/acre/year
had 18% more dry matter than the same varieties treated
with 210 1b N. Schippers (1968) reported both linear and
optimum responses with increased N in the four varieties he
studied.

Table 1 shows the effects of increasing N rates on

the variety Superior as reported by Wilcox and Hoff (1970).

12

Table l.—-Inf1uence of increasing N rates on total solids,
total protein and non-protein nitrogen.

 

 

N rate % Dry % Total Dry matter Total
(lb/acre) matter protein production protein
(DW) (lbs/acre) (lbs/acre)
36 22.4 9.5 7930 307
111 21.6 10.9 8964 401
186 21.3 11.5 8989 434
336 21.3 12.9 8840 479

 

In the analysis of the non-protein nitrogen fraction, Hoff
(23 31., 1971) found that the free amino acid pool doubled
when the rate of N was increased from 36 lbs to 336 lbs,
62% of the increase occurring with the first increment of
N. A5partic and glutamic acids and their corresponding
amides constituted the bulk of the pool and increased from
55% to 65% with increasing N rates. Free methionine in-
creased 1.4 times at the highest N rate but its relative
proportion in the pool decreased from 2.2% to 1.6%. Free
methionine expressed as a percent of the total N increased
from .619% to .659% with the second increment, further
increasing to .741% and then decreasing to .619% with the
fourth increment.

Mulder and Bakima (1956) concluded that the effect
of mineral nutrition on the amino acid content works mainly
through the protein content of the tuber. The N composition
of tubers grown in soils poor in N, P, K, and magnesium,
fertilized with the deficient element was found to respond

in a consistent manner. Responses to P, K, and Mg are

13

similar to those at low levels of N fertilization. The
higher N rate resulted in tubers having higher N contents,
lower protein/total N ratios and higher amide N/non-protein
N ratios. Conversely the higher rate of P, K, and Mg
resulted in lower N contents, higher protein/total N ratios,
and lower amide N/non-protein N ratios. Amino acid analy-
sis indicated no difference in composition of the amino
acids in the protein, but considerable variability existed
in the composition of the non-protein N fraction primarily
due to the amide N. Thus no correlation existed between
the amino acid composition of the protein and that of the

non-protein fraction.

Effects of storage

Separating a sample of Katahadin tubers into high,
intermediate and low specific gravity classes and storing
them for nine months at 38 F, Talley (gt 31., 1961) con-
cluded that regardless of the specific gravity class, the N
constituents were affected the same. In each class, N
content increased with a progressive decrease in dry matter
amounting to 7% at the end of the storage period. The
ratio protein N: total N also decreased 17% over the
entire period. Later (1964) he found an inverse relation-
ship to exist between dry matter and free amino acids
within any one Specific gravity class over the storage
period. When calculated on a fresh basis this relationship

was less evident.

14

Effects of variety and location on nitrogen content
Neuberger and Sanger (1942) found wide differences
in the dry matter and composition of 11 varieties grown in
the same field in one year. Table 2 contains those varie—
ties representative of the extremes of each characteristic,

being ranked on the basis of N content.

Table 2.--Effect of variety on nitrogen content and

 

 

composition.
Protein N as
% N % N a percent of
Variety (DW) (FW) total N % Dry matter

Redskin 1.95 .319 37.5 16.37
Arran Banner 1.65 .314 37.0 18.99
Keer's Pink 1.48 .238 58.0 16.82
Golden Wonder 1.38 .305 63.7 21.96
Dunbar Std. 1.16 .236 44.9 20.37

 

In the analysis of 12 varieties grown in the same

field under similar conditions Mulder and Bakima (1956)

found total N on a dry basis to range from 1.22-1.97% while

the proportion of protein N remained consistent regardless

of N content.

Nash's data (1941) indicated variety x location

interaction for the components studied in eight varieties

all grown in three diverse locations in a one year period.

Varieties containing the highest and lowest concentrations

of N on a dry basis tended to be associated with low and

high dry matter contents which in turn were associated with

low and high starch contents.

Higher proportions of

15

protein N to be associated with those varieties containing
lower N contents on a dry basis. On a fresh basis, those
varieties containing higher dry matter tended to contain
more protein N than those varieties containing lesser
amounts of dry matter. Location-wise, opposite effects were
noted. Higher proportions of protein N and total N on a

dry basis were associated with those locations producing
high dry matter tubers.

Table 3.--Effects of variety and location on dry matter,

starch and protein content (data from Nash,
(1941)).

Protein N as

 

 

% N a percent of % Starch

Variety (DW) total N % Dry matter (DW)
Earline 1.76 58.1 19.25 70.5
Katahdin 1.72 65.6 21.48 73.6
Chippewa 1.70 58.9 18.30 71.9
Warba 1.67 60.2 20.68 75.2
Sebago 1.63 70.7 21.38 72.5
Cobbler 1.53 69.5 21.05 73.2
Green Mt. 1.41 68.4 23.73 75.2
Houma 1.38 66.8 21.93 77.1
Locationa

I 1.75 68.6 22.14 75.9
II 1.62 68.6 22.88 73.8
III 1.52 58.7 18.67 71.4

a Silt loam, II Silt loam, III

In a similar investigation over a period of three

years, Talley (g£_gl., 1970) found that varieties,

locations,

years,

and their interactions all contributed in

16

varying degrees to the total variability in free methionine,
total protein and free nitrogen (Table 4).
Table 4.--Percent of total variance in methionine, total

protein, and free N/total N contributed by years,
locations, varieties and their interactions.

 

% Total protein Free

 

Source DF Methioninea (DW) N/total N
Replication 1 .3 0.0 0.0
Years 2 9.6 0.0 0.9
Locations 5 8.2 32.6 5.0
Varieties 4 29.0 0.0 31.4
Y x L 10 17.0 15.8 9.2
Y x V 8 2.1 7.6 0.1
L x V 20 8.6 12.3 10.0
Y x L x V 40 11.7 22.0 15.7
Residual 83 13.7 9.7 28.0

 

aMicromoles free methionine/l g dry matter.

Metzger (g£_al., 1937) in studying the composition
of the potato found that protein, total solids and starch
content differed significantly between varieties, locations
and years (Table 5). He did not give reference to inter-
action.

Eliminating climatogical differences, Goldthwaite
(1925) reported compositional differences of tubers of the
variety Rural grown by different growers in one specific
locality. Her results are reported in Table 6.

Making over 5,000 determinations on 12 varieties of
potatoes grown under diverse environments she concluded

that there is no definite percentage composition of any

Table 5.-—Effects of variety,
matter, starch and protein content (data from
Metzger (33 31., 1937)).

17

location and year on dry

.__

 

Variety % Protein (DW) % Dry matter % Starch (DW)
Triumph 11.39 20.45 64.9
Cobbler 10.50 20.01 77.4
Katahdin 9.90 21.82 69.1
Peachblow 9.77 23.13 72.2
Locationa
I” 11.22 20.04 65.8
II 10.37 24.32 74.1
III 10.29 21.87 70.6
IV 10.25 20.79 68.9
V 9.24 23.37 71.6
Year
1936 10.70 22.05 69.0
1934b 10.34 20.89 72.5
1935 9.75 23.29 69.9

 

aCommercial locations within Colorado.

bDescribed as arid.

18

Table 6.—-Composition of Rural potatoes as affected by
cultural practices.

— -— w:-

% Protein

 

Grower (DW) % Dry matter % Starch (DW) % Ash (DW)
I 12.86 22.40 68.0 4.10
II 10.20 20.98 70.5 4.69
III 8.91 20.59 73.3 4.57

 

variety but when compared between growers or locations,

varietal differences do indeed exist.

PART I

THE EFFECTS OF VARIETY AND LOCATION AND
THEIR INTERACTION ON PROTEIN

QUANTITY AND QUALITY

INTRODUCTION

The effects of variety and location on total protein
has been reported on by Talley (eg 21., 1970), Goldthwaite
(1925), Metzger (EE.21°' 1937), Nash (1941), and Neuberger
and Sanger (1942). Luescher (1972) in analyzing numerous
selections, related the composition and contents of protein
and non-protein nitrogen fractions and available methionine
contents to protein quality. He and others (Kies and Fox,
1972; Rios, 1969; Williams, 1959) have demonstrated that
methionine is the first limiting amino acid of potato
protein. In the same study he reported heritabilities of
available methionine to range from 79% to 100%.

The purpose of this study was to examine the effects
of variety, location and their interaction on total protein,

available methionine, and protein quality.

19

MATERIALS AND METHODS

Sixteen varieties of potatoes, all included in the
North Central Regional trials of 1971 were selected for
this study. The varieties 36097-9, Neb. 1.57, Norland,
Cobbler, ND6925-13, N07196-18, Red Pontiac, W629, B6024-3,
B6139-11, 86116-18, La22-111, N49.62-5, N93.55-16, ND6993-13,
and W634 each from a common seed source were grown at
experiment stations in North Dakota, Kansas, Nebraska,
Wisconsin, Missouri, Louisiana, Michigan, Ohio, and two
locations in Indiana. General environmental data for each
of these locations are described in Appendix 1.

At or shortly after the respective harvest date,
five tubers of each variety were randomly selected and sent
to Michigan State University. Upon arrival, the specific
gravity (Appendix 2) of each five tuber sample was deter—
mined by the weight in air-weight in water method (Isleib
and Thompson, 1957). Four longitudinal slices were cut from
the middle of each of the five tubers, quick frozen, com-
posited, and freeze dried. Dried samples were ground to to

mesh in a Wiley Mill and stored in screw cap bottles.

20

21

To estimate the magnitude of variability contri-
buted by locations and the variety--1ocation interaction,
mean squares were estimated for replication and variety x
replication within location from a similar but smaller set
of data (Table 7). This data consisted of a five tuber
sample from each of four replications of the first eight
above mentioned varieties grown in Michigan in 1972 and
were analyzed in the same way as samples from the unrepli-
cated experiment. Use of these estimates is based on the
assumption that these mean squares are similar for all
varieties grown in all locations in 1971.

The denominator mean square used to perform the
F-test for locations was derived from Satterthwaite (1946)
where:

Xi
V2

L = (MS - MSS) + MS

4 3

and where the degrees of freedom associated with L is:

_ L2
V“ 2 2
(VI/V2 x M84) + (M83) /df3
4

where df3 and df4.are the degrees of freedom associated

with their reSpective mean squares.

Determination of total protein
Total protein (N x 6.25) was determined by the

semi-micro Kjeldahl method described by Henwood and Gary.

22

Table 7.--Expected mean squares, their degrees of freedom and F-ratios
in the analysis of variance.

 

 

Source df MS EMS F-ratio

Location 9 1 02 + r02 + 02 + rv 02L MS /L
VR(L) LV v1 R(L) l 1

Variet 15 2 02 + r02 + r02 MS /MS

y vaun LY v 2 3

V x L 127 3 02 + :02 MS /MS
VRUJ LV 3 5

Rep. 2 2

(M1ch.) 3 4 O VR(L) + v20 R(L) MS4/MS5

V x R
(M1ch.) 21 5 O

 

Determinations were made in duplicate and repeated if they
differed by more than 3%. Protein values reported in
Appendix 2 are adjusted to zero moisture for easier con-

version to a fresh weight basis.

Determination of "available" methionine

The method of Luescher (1971) was adapted for the
determination of "available" methionine.1 Samples were
weighed to contain an equivalent of 50 mg (N x 6.25). After
weighted samples were placed into 4 oz. screw cap bottles,

20 m1 of citrate cyanide buffer was added. The pH was

 

1Methionine in an enzymayic digest which is avail-
able to‘g. zymogenes as measured by growth determined on a
methionine stan ar .

23

adjusted to 7.2 with N KOH and the container placed into a
water bath at 56 C. Two m1 of 4% W/V crude papain in
citrate cyanide buffer at pH 7.2 was added and incubated
with intermittent shaking for 3 hours at 56 C. The pH of
the digests was adjusted to 7.2, filtered, and diluted to
100 ml with distilled water.

Triplicate portions of 0, 1, 2, 3, 4, 5, and 6 m1
of the standard methionine (5 ug l- met/ml) were distributed
into 16 x 150 mm test tubes. Duplicate 2 m1 portions of
each sample were pipetted into the same sized test tubes.
Two m1 of basal media and 1 m1 of the amino acid supplement
were added to each test tube and brought to a final volume
of 11 ml with distilled water. After capping each tube,
samples were sterilized with flowing steam for 12 min. and
then cooled. One drop of inoculum culture (g. gymogenes)
diluted 1:10 with .85% saline solution was added and
incubated at 37 C for 48 hours.

After incubation, tubes were heated in flowing
steam for 10 min., stoppered and shaken vigorously, and set
aside for 30 seconds. The optical densities of the cultures
were then measured with a Hitachi Perkin-Elmer 139 UV-VIS
spectrophotometer (flow through cell) at 580 mu. The above

analysis was repeated again on a different day.

Determination of biological value of potato_protein
The method used to determine the biological value

of the potato samples is the same as that used in the

24

determination of "available" methionine, except that the
amino acid supplement was omitted from the samples.
Triplicate portions of 2 and 4 m1 of the papain digest
containing 50 mg casein protein/100 ml digest (prepared in
the same manner as sample digests) were distributed in 16 x
150 mm test tubes. Two m1 of basal medium was added and
the final volume brought up to 10 ml with distilled water.
Duplicate 2 and 4 m1 portions of potato sample digest were
treated in the same way.

The average growth response of the standard casein
growth cultures were determined at each concentration.
Culture growth in the potato samples as a proportion of the
standard casein culture was a measure of the biological
value of the potato nitrogen (Appendix 2). Optical density
values were determined at 580 mu. The above analysis was

repeated again on a different day.

Discussion of S. zymogenes

_S. zymogenes has an absolute requirement for
exogenous lucine, methionine, tryptophane, isoleucine,
arginine, histidine, valine, and glutamic acid, the first
four amino acids being essential to man. It is powerfully
proteolytic and grows quickly with an adequate intact
protein as the main source of nitrogen (Ford, 1960). While
chemical hydrolysis may cause destruction or unavailability
of certain amino acids, or cause destruction of inhibitory

substances, enzymatic digestion permits measurement of the

25

available amino acids which may be more indicative of con-

ditions in "vivo" (Evans and Butts, 1948).

Determination of netgprotein

With the exception of sample weight, the average
net protein content for each variety and location was
determined by the biological value method. After drying,
1 g. of each sample, representing a variety and location,
was composited by variety and by location. Digests con—
taining 400 mg. of the composited sample were then carried
through the same procedure as in the biological value analy-
sis. Average sample culture growth as a proportion of the
average standard casein culture growth (50 mg casein/100 m1
digest) was a measure of the protein contained in the
potato sample which is equivalent to the same amount of
casein protein. Net protein per lg of dry matter is
calculated as:

Absorbance of Sample Growth

Absorbance of Std. Casein Growth X 50 mg caseln X 2'5

Determination of the relative uality‘ofgpotatogprotein
minus the effects of "available methionine

The relative quality of the potato protein minus
the effects of available methionine was determined by
dividing the average growth of S. zymogenes in the methio-
nine analysis by the average growth in the biological value
analysis utilizing two m1 concentrations only. As a result

of using the same digest in both analyses, the same

26

concentration of methionine was present in each set of
tubes. Therefore the greater growth responses of cultures
used in the methionine assay are assumed to be a result of
the supplemented amino acids present in optimum amounts.
Less growth of cultures used in the biological value assay
is due to a less than optimum amino acid balance, therefore
it is assumed that the magnitude of the difference between
the absorbance readings of these two analyses (for each
sample) is indicative of the degree of quality of the
nitrogen constituents minus the effect of "available"

methionine.

RESULTS AND DISCUSSION

Contribution by varieties and location to the total
variability in "available" methionine, total protein, total
dry matter, BV and relative protein quality was found to be
significant. The variety-location interaction also contri-
buted significantly to all those variables except relative
protein quality (Appendix 4). Thus variety and location
means (Table 9) and the observations contributing to them
can be placed into high, intermediate and low classes with
overlapping of observations between adjacent classes but
rarely between the extreme classes (Appendix 2). The
variability due to variety, location, variety-location
interaction and error, expressed as a percentage of the
total variability for each of the above variables, are
reported in Table 8. Average values of the eight varieties
grown in Michigan over a two year period are reported in
Appendix 3.

Aside from several weak trends, the parameters
included in the environmental data could not be related to
differences within varieties grown over all locations

(Appendix 2). Specific gravity was highest in those

27

28

Table 8.--Percent contribution by variance components to the
total variability in "available" methionine,
total protein, total dry matter, BV and relative
protein quality.

 

 

Relative

Source of Dry Total protein "Available"
variability matter protein BV quality Methionine
02 location 42.5 46.7 34.2 58.4 31.5
02 variety 27.7 20.1 17.8 22.6 42.8
02 var x 10C 16.0 17.2 35.5 8.0 13.2
02 rep (10C) 0.0 0.0 0.0 0.0 0.0
02 error 13.8 16.0 12.5 11.0 12.5

 

potatoes grown in locations described as having optimum
growing conditions (North Dakota, Wisconsin, Nebraska) and
lowest in Indiana mineral soil, where high temperatures
prevailed, Indiana muck, were 300 lb KCL/acre was applied
and in Louisiana where poor drainage existed. In Michigan,
a very high rate of nitrogen application was associated
with high total protein and available methionine contents
and a low BV of the contained protein.

Potatoes prOduced in Indiana muck expressed the
greatest range in BV, available methionine and protein
content while potatoes from Missouri ranged least in these
variables. The greatest range in relative protein quality

was expressed in potatoes from Michigan and North Dakota

while potatoes from Louisiana ranged least in this variable.

29

The variety La 22-111 was outstanding in that it
expressed the greatest range in each of the above mentioned
variables. The variety Neb 1.57-1 expressed the least
range in BV and relative protein quality while the varie-
ties ND 6993 and B 6139-11 expressed the least range in
"available" methionine content and protein content
respectively.

Considered individually, little relationship existed
between BV and "available" methionine and BV and relative
protein quality (Table 9), but when considered in com-
bination, the influence of these variables on BV becomes
more meaningful. When all observations were allocated into
classes having high, intermediate, and low relative protein
qualities and "available" methionine contents (independent
of variety or location), an increasing gradient in BV was
observed with increases in these variables (Figure 1).
Based on this relationship, differences among mean bio-
logical values (Table 10) can be better explained. A low
relative protein quality, indicative of a poor amino acid
balance, depressed the benefit of higher "available"
methionine contents. Similarly, the benefit of a high
relative protein quality, indicative of a better amino acid
balance was depressed by low methionine contents.

While an increased relative protein quality or a
higher methionine content would increase the BV, greater
responses would be expected when the most limiting component

is upgraded. The relationship between relative protein

30

Table 9.--Correlations among "available" methionine, total protein (dry
basis), total solids, BV, relative protein quality, total
protein (fresh basis), "available" methionine/g dry matter
and available methionine/g fresh weight (data from 16
varieties grown in 10 locations).

 

 

2 e
-r-'I A .2
8%. a a or.
"45 v -8 :20
‘510 c u e u o~
0". 'H m O>1 -H’- 0\
E‘\ m 'o H p m - E u
«IJ u «4 CL-H 4"; 9’
o o o .4 r4 0 0 E
.4 E H o o m u .4
.8 04 U) >25 04.1: at?
61 -a 0' m s
HE H H 4.) H0 r-l
-a m m m a u -H
8 8 8 e .. 82: e
4 B B m A a e
"Available"
methionine
mg met/16 mgN 1.00
Total protein
(DB) .11 1.00
Total solids -.14 -.44** 1.00
BV .37** -.28** -.21** 1.00
Relative pro-
tein quality -.77** -.26** -.02 .26** 1.00
Total protein
(F8) -.01 .62** -.02 -.07 —.28** 1.00
"Available"
methionine
ug met/g DM .75** .73** -.08 .09 -.72** .42** 1.00
"Available"
methionine
ug met/g FW .71** .52** -.18** -.O6 -.77** .69** .84**

 

*significant at P = .05.

**significant at P

.01.

31

BV and relative protein quality

co. 1

ca. .

 

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muaamso cflopoum m>wuwamu one mchoHnumE maanHm>m mo menopamcH .H madman

ocficofieeos oumfipoasopcfi ocfl:0fi£poe 30H

 

 

onwcofleuoe Ame:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

.e.
..
n .1 .. .... l .
1H 1.... . e
.1. . u
. r .L
”In... .. I e . .
r... u .1 .
e. em .a n We
........ Tl . .8. .ll . .3. v... Fl
...v m. ..,...r w m“. .
Jammy. an. rlll- [
e... .n
r e g
ocficofifioa manager/4. U
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.5293 5530.5 Passage I

>m E0

sc.H

ue.H

 

euruotqiam GIQB[IBAB

Table lO.-Mean values of varieties and locations for ”available” methionine, relative protein

32

quality, BV, total protein (dry basis), calculated net protein content and

theoretical net protein content.

 

 

. a "Calculated" "Theoretical"b
mg met/ Relative protein % Protein mg net protein/g mg net protein/g
Variety 16 mg N quality BV (DW) dry matter dry matter

ND 7196-18 1.16 .490 .66 11.5 81 77
Neb 1.57-1 1.25 .490 .68 13.4 91 92
N 629 1.27 .488 .69 13.9 94 96
N 49.62-5 1.36 .459 .68 12.7 90 88
N 93.55-16 1.23 .455 .63 12.0 73 75
cobbler 1.55 .459 .73 11.2 80 82
B 6024-3 1.41 .452 .69 13.1 91 90
Norland 1.51 .439 .69 14.0 94 96
D 6139-11 1.54 .435 .70 10.9 76 76
Red Pontiac 1.61 .435 .72 12.7 93 91
W 634 1.54 .427 .69 12.3 84 84
8 6097-9 1.63 .429 .72 11.5 84 86
ND 6993-13 1.55 .418 .68 12.7 86 87
La 22-111 1.64 .422 .71 13.6 94 97
ND 6925-13 1.63 .418 .70 13.1 90 92
3 6116-18 1.71 .413 .71 13.3 95 95
Location

Ind. Mineral 1.20 .518 71 13.3 95 94
Missouri 1.35 .469 68 12.8 89 87
Nebraska 1.38 .472 71 12.0 86 85
Ind.-Muck 1.49 .459 72 12.6 93 89
N. Dakota 1.38 .444 67 10.9 79 73
Louisiana 1.52 .461 75 12.6 93 94
Wisconsin 1.47 .422 66 11.9 84 80
Kansas 1.59 .435 71 11.1 81 78
Ohio 1.64 .418 70 14.8 100 104
Michigan 1.66 .376 64 14.8 95 94

 

aRelative protein quality - l/

b

averaged).

absorbance methionine assay
absorbance BV assay/1.1

Theoretical net protein - BV x % protein (calculated for each observation and

33

quality and "available" methionine (r = -.77) suggests
difficulty in developing a variety with such an optimum
balance, however the variety Cobbler approaches this.

Though the magnitude of the relative protein quality
was indicative of amino acid balance, factors influencing it
were not identified in this study.

In discussing the cause of variation in "available"
methionine in potato protein, Luescher (1972) reported that
free methionine was highly correlated with available
methionine (r = .96) and accounted for 93% of the total
variability in "available" methionine contents. While free
methionine tended to increase with increasing non-protein N
contents (r = .30), the EV of the non-protein N decreased
as non-protein N contents increased (r = -.96) the latter
also increasing as total protein increased (r = .63). A
correlation of (r = -.69) between the EV of the total
protein and total protein content was also found.

These trends indicate that as non-protein N in-
creases, the amino acid composition becomes less balanced.
In regards to the study of Mulder and Bakima (1956, this
lack of balance may be due in part to increasing amide/non-
protein N ratios.

If the above is considered in this study, then the
observed negative correlations between the relative protein
quality and total protein (r = -.26) and BV and total
protein (r = 0.28) are logical. However, varieties

(N 1.57-1 and W 629) and locations (Indiana muck) can be

34

identified as having both a high total protein content and

a high relative protein quality. In these cases an increase
in "available" methionine would seemingly increase the BV of
the protein also resulting in an increased net protein
content.

The calculated net protein contents of composited
samples by variety and location were within the range of
theoretical net protein contents (Table 10). Thus it can
be assumed that for any one sample, the net protein content
can be calculated by obtaining the product of BV and total
protein content. It follows that potatoes, of a variety or
from a location, having a high BV will not necessarily
contain high amounts of net protein due to differences in
total protein content.

From a nutritional point of View a potato containing
large quantities of protein high in BV is to be desired but
from a breeding point of view, difficulty in developing a
variety with such a combination (both on a dry and fresh
basis) is suggested from inverse relationships occurring
among the involved factors.

In a breeding program for improved protein quality,
the variation due to varieties, and the environment in
which they are grown and the possible variety-environment
interactions must be considered. Based on this study, all
of these factors contributed in varying degrees to quality

and quantity components.

35

Due to the diversity of the environments in which
these varieties were grown, it is not surprising that
environmental data could not be related to locational
differences in protein quality and quantity. Thus the
nutrient availability of the soils and environmental factors
influencing nutrient accumulation and its distribution 1n
the tuber become important.

Equally important is the fact that varietal differ-
ences exist in protein quality and quantity and that
accumulation and distribution of nitrogenous constituents
as influenced by variety are subject to variation due to
environmental influences. The fact that some varieties do
not respond in a consistent manner relative to other
varieties when grown over different locations should also
be considered.

Since locations dictate to a great extent the
relative protein quality and available methionine contents,
selection of parents and offspring for improved protein
quality should be conducted where cultural methods are
representative of the area of production and should be
based on upgrading the methionine content and/or relative
protein quality. Identification of factors influencing the
latter merits further study.

The fact that large differences in quantity and
quality factors were detected among genotypes grown in

diverse locations is significant in that a great potential

36

exists for improvement of these factors through breeding.
If the variety-year interaction is small, gain within any

one location would be actual.

SUMMA RY

Variability due to variety, location of growth and
their interaction contributed in varying degrees to the
total variability found in total protein and "available"
methionine contents, relative protein quality and BV of
the protein of 16 potato varieties grown in 10 state
locations. Environmental data could not be related to
noted differences between locations for any one variable.

Relationships among the above variables in addition
to net protein contents are discussed. Based on these
relationships, both an increase in ”available" methionine
content and the relative protein quality should be con-
sidered in a breeding program aimed at improving the
utilization of potato protein. Ultimately, a potato con-
taining high amounts of total protein of high quality should
be sought. Due to environmental influences, it is sug—
gested that such a program be confined to a locality

representative of the area of production.

37

PART II

PROTEIN QUALITY OF WHOLE POTATO FLOUR AND
AIR CLASSIFIED FRACTIONS AS MEASURED BY

RAT AND MICRO-BIOLOGICAL ASSAY

INTRODUCTION

Chick and Slack (1949) studied potato protein
quality of the total protein and various fractions of it as
measured by rat assay, however a standard was not utilized.
Rios (1969) found varietal differences in potato protein
quality as measured by vole assays and concluded that
supplemented methionine increased the quality of the
protein.

Shaw and Shewy (1972) reported on the production of
potato starch utilizing air classification and thus
collecting a solid, high protein by-product. Though
feeding experiments were not conducted, they suggested the
possible use of this by-product as a feed supplement.

The purpose of this study is to: (a) compare the
protein quality of air-classified potato flour to that of
unaltered whole flour; (b) determine the quality of the
potato protein relative to casein; and (c) compare protein
quality as determined by rat assay to protein quality as

determined by micro-biological assay.

38

m0
tc

f1

we

re

s]

MATERIALS AND METHODS

The cultivar Merrimack 58, previously stored for 4
months at 45 F was selected for this study. The average
total solids and crude protein content of this lot was

found to be 21.6% and 3% (fresh weight) respectively.

Preparation of whole flour

Approximately 18 kg of large and small washed tubers
were autoclaved at 15 p.s.i. for 15 and 10 minutes
respectively. After removing the periderm, tubers were
sliced, quick frozen and freeze-dried. This material was

then milled to 30 mesh and stored in plastic bags at -10 C.

Preparation of concentrate flour

Approximately 23 kg of tubers were washed, lightly
peeled, sliced, quick frozen and freeze-dried. This
material was milled to 30 mesh, dried at 30 C and classified
utilizing the Walther laboratory air classifier. Air
classification yielded two fractions, namely, a fine
fraction containing cell wall material and small starch
grains, and a coarse fraction containing small amounts of

cell wall material and large amounts of medium and large

39

40

starch grains. It was necessary to reclassify the coarse
fraction in order to obtain maximum yields of crude protein
in the fine fraction. Periderm material was largely un-
millable as evidenced by large amounts of periderm residue
within the mill after a milling operation.

Aside from periderm losses the efficiency of the
operation, as reflected by the composition of the whole
flour and air-classified fractions derived from it, are
.reported in Table 11.

Table 11.--Composition of a 1 kg portion of whole potato
flour and air-classified fractions derived from

 

 

it.
Protein as a
Grams Grams percent of
dry total initial total Percent
Component matter protein protein moisture
Whole flour 1000 131.9 5.0
Fine fraction 292 91.5 69.5 5.0
Coarse
fraction 678 33.6 25.5 5.0

 

Preparation of diets

In a preliminary study, weanling rats fed the raw
concentrate at a level of 9% protein for a period of 5
days, barely maintained their initial weight. It was noted
that food consumption was very low, but when fed the con-
centrate in a cooked form, feed intake and weight gain

resumed to normal levels. It was noted that the uncooked

41

version had a very sharp bitter taste which disappeared
after cooking. Also the adverse effects of feeding larger
sized starch grains, characteristic of potato starch, were
considered (Harper, 1971; Morrison, 1936).

Thus before incorporation into the diets, it was
necessary that both the whole and concentrate flours be
cooked. Due to the destruction of physical properties upon
cooking, air classification of whole cooked flour is not
possible. Therefore it was necessary that the concentrate
be cooked after air classification. This was done by
adding the concentrate to boiling water in a ratio of 1:4
and heating over an open flame for 7 minutes. The resulting
smooth paste was then freeze-dried and milled to 30 mesh.

With slight modifications, diets were made up in
accordance with AOAC (1970). The whole and concentrate
potato flours and casein were analyzed for nitrogen (Henwood
and Gary) and moisture content prior to incorporation into
the diets (Table 12). So that all diets contained calories
derived from potato starch, commercial potato starch was
added in necessary amounts to the concentrate flour and
casein diets to equal that present in the whole flour diet.
Before addition to the diets, the starch was gelatinized,
dried and milled to pass a 35 mesh sieve. The amounts of
added components and final composition of the diets are
reported in Appendix 5. Small differences in caloric values

are due to the crude fiber in the potato diets.

42

Table 12.--Composition of casein, whole, and high protein
concentrate potato flours.

 

% a % % % % % Starch
Protein Ashb Watera Fiberb Fatb + sugarC

 

Whole

flour 13.10 3.70 7.0 1.60 .8 73.80
Fine d

fraction 32.93 3.70 5.0 5.25 .8 52.32
Casein 87.00 .71 9.6 -0- 1.2 1.40

 

aAverage of six determinations: Protein = Kjeldahl
N x 6.25.

bApproximate values; Watt and Merrill, 1963.

cEstimated by assuming all nitrogen is protein in
nature and substracting values of other components from
100.

dCrude fiber expected to increase 3.3 fold since

fine fraction contains 30% of initial dry matter and major
portion of cell wall material.
Determination of proteinuguality

Protein efficiency ratios (PER) and nitrogen incor—
poration efficiencies (NIE) (Stucki and Harper, 1962) were

used to evaluate the quality of the test diets as compared

to casein, where:
PER = Weight gain (g)/g (N x 6.25) consumed
and

N retained in carcass x 199

NIE = N consumed

43

For three days before starting the test diets, 21
day old male Sprague Dawley rats were fed a starter diet.
At the end of this period, 10 rats were assigned to each of
four groups such that the range in weight of any one group
was not greater than 11 g while mean weights between groups
did not vary by more than .49. Food and water was provided
29.112.t° three of these groups while the fourth group was
killed (body composition controls). The weighed carcass
(minus the gastrointestinal contents) of each of these rats
was autoclaved, homogenized, and diluted to a final volume
of 1400 ml. with distilled water. Duplicate 50 m1 portions
of the homogenate were predigested with an equal volume of
concentrated sulfuric acid and after cooling brought up to
a final volume of 100 ml with distilled water. Duplicate
2 m1 portions of each predigest were then analyzed for total
nitrogen. The remaining rats were killed at the end of a
26 day period and the carcasses treated in the same manner.
The nitrogen retention was calculated as the body nitrogen
content of the test animals minus that in the body compo-
sition controls.

The method used in this study to determine protein
quality as measured by enzymatic digestion and micro-
biological techniques is the same as in Part I of this

thesis.

RESULTS AND DISCUSSION

Results of this study are presented in Tables 13,

14, and 15.

Raw observations are reported in Appendix 6.

Table 13.--Means and ranges of rat responses as influenced
by casein and potato diets.

 

 

Meansa and
Diet Variable Their S.D. Range
Whole flour 2.34a : .21 2.10 2.73
Concentrate PER 2.23a i .12 2.05 2.40
Casein 3.02b i_.22 2.71 3.29
Whole flour .436a : .046 .358 .488
Concentrate NIE .434a :_.041 .354 .498
Casein .587b i .042 .535 .662
Whole flour 32.0a ‘1 3.8 27.5 38.4
Concentrate Protein 31.4a : 4.2 25.3 39.2
Casein Consumed (g) 35.3a 1’3.5 30.8 40.7
Whole flour 75.0a ‘1 12.2 63.0 99.0
Concentrate Weight gains 69.7a i_1l.l 60.0 94.0
Casein (g) 106.6b i 13.6 90.0 132.5

 

aMeans followed by the same letter are not signifi-

cantly different at the .01 probability level using Tukey's

test.

44

45

Table l4.--Corre1ations among PER, NIE, protein consumed
and weight gain.

 

 

 

PER NIE Protein consumed
NIE .92**
Protein consumed .42* .31
Weight gain .88** .77** .79**
*Significant at P = .05.
**Significant at P = .01.

Table 15.--Micro-organism growth and rat responses on
potato diets as a percent of casein.

 

a

 

BV PER NIE Weight gain
Whole flour 73 77.5 74.3 70.4
Concentrate 76 73.8 73.9 65.4
Average 74.5 75.7 74.1 67.9

 

aAverage of 6 determinations/sample.

46

PER determinations of this study are very meaningful
as a result of nearly equal food consumption by all test
groups. No differences in protein quality or food consump-
tion were noted between the whole and air classified potato
flours, therefore it can be assumed that air classification
neither added nor detracted from the protein quality nor
other characteristics which might alter consumption when
fed in a cooked form.

Both PER and NIE appeared to be equally effective
measurements for evaluating potato protein quality. The
high correlation coefficient (r = .92) between them is in
agreement with that of Bajaj (25 21., 1971). Thus, due to
the added labor required to determine NIE, the PER method
would seem to be preferred especially when food consumption
is nearly the same in all test groups.

Of significance is the fact that very similar
results were obtained by the BV method utilizing g.
zymggenes. This is not surprising for several reasons.
This organism has an absolute requirement for exogenous
leucine, methionine, tryptophane, arginine, histidine,
isoleucine, valine, and glutamic acid (Ford, 1960) while
all of these except glutamic acid are essential for the
rat. Further, enzymatic digestion does not cause
destruction of amino acids or inhibitory substances as does
chemical hydrolysis (Evans and Butts, 1948). Thus growth
of this organism, (described as being powerfully proteoly-

tic and growing quickly with an adequate intact protein

47

(Ford, 1960)) in such a digest may closely correspond with
results in "vivo."

Though meriting further study, the potential of this
method in evaluating protein is great. In a potato breeding
program for improved protein quality, literally thousands
of selections could be evaluated due to low labor, time and
cost factors.

Present day starch production operations, utilizing
wet methods results in waste of and pollution by a potenti-
ally recoverable, high quality, high protein by-product.
Aside from important economic considerations, the fact that
large quantities of a ”flour” containing up to 35% protein
derived by air classification is of importance. The
relatively high quality of the contained protein, when
cooked, could be utilized in a food or feed supplement.
Further increases in its quality by up-grading components
influencing its quality through supplementation (Part I of

this thesis) would add to its dollar value.

SUMMARY

By air classification techniques, a concentrate
flour containing 33% protein was derived from whole potato
flour containing 13% protein. When fed to weanling rats in
a cooked form, no differences were found in food consumption
or protein quality between whole potato flour and the con-
centrate derived from it. Based on protein efficiency
ratios, nitrogen incorporation efficiencies and weight gain
measurements, the responses of rats fed potato diets as a
percent of the responses of rats fed casein were 76%, 74%,
and 68% respectively. The protein quality of the potato
flours as determined by a micro-biological method utilizing

g. zymogenes were very comparable to those values determined

 

by rat assay.
The potential of air classification in the potato
industry and of micro-biological evaluation of potato

protein is discussed.

48

LITERATURE CITED

LITERATURE CITED

Association of Official Agricultural Chemists 1970. 11th
ed. Washington, D.C.: Association of Official
Agricultural Chemists, p. 801.

Bajaj, S., Mickelsen, 0., Baker, L. R., and Markarian, D.
1971. The quality of protein in various lines of
peas. Br. J. Nutr. 25, 207-212.

Burton, W. G. 1966. The Potato: A Survey of its history
and of factors influencing its yield, nutritive
value, quality and storage. 2nd ed. In the distri-
bution and composition of the dry matter in the
potato tuber. H. Veenman and Zonen N. V., Wagenin—
gen, Holland, pp. 143-169.

Chick, H., and Slack, E. B. 1949. Distribution and
nutritive value of the nitrogenous substances in the
potato. Biochem. Jour. 45, 211-221.

Cobb, J. S. 1935. A study of culinary quality in white
potatoes. Amer. Potato J. 12, 335-346.

De, R., and Singh, R. 1959. Effect of nitrogen fertili-
zation on yield and chemical composition of potato.
Indian Potato J. 1, 76-83.

Dunn, L. E., and Rost, C. O. 1948. Effect of fertilizers
on the composition of potatoes grown in the Red
River Valley of Minnesota. Soil Sci. Soc. Amer.
Proc. 13, 374-379.

Evans, R., and Butts, H. A. 1948. Studies on the heat
inactivation of lysine in soybean oil meal. J.
Biol. Chem. 173, 15-20.

Fagen, T. W. 1925. The variation in the moisture and

nitrogen content of the potato during growth and
storage. Welsh J. Agric. 1, 110-115.

49

50

Ford, J. E. 1960. A microbiological method for assessing
the nutritional value of proteins. Br. J. Nutr.

Goldthwaite, N. E. 1925. Variations in the composition of
Colorado potatoes. Colorado Exp. Sta. Bull. No.

Harper, A. E. 1959. The Yearbook of Agriculture. Y.S.
Dep. Agr. p. 91.

Heinze, P. H., Kirkpatrick, M. E., and Dochterman, E. F.
1955. Cooking quality and compositional factors of
different varieties from several commercial
locations. U.S.D.A. Tech. Bull. No. 1106, 1-69.

Henwood and Gary. The Hengar Company. 6825 Greenway Ave.
Philadelphia, Pa.

Hoff, J. E., Jones, C. M., Wilcox, G. E., and Castro, M. D.
1971. The effect of nitrogen fertilization on the
composition of the free amino acid pool of potato.
Amer. Potato J. 48, 390-394.

Isleib, D. R., and Thompson, N. R. 1957. Potato handling
equipment for use in experimental work. Amer.
Potato J. 35, 70-71.

Kies, C., and Fox, H. M. 1972. Effect of amino acid
supplementation of dehydrated potato flakes on
protein nutritive value for human adults. Jour.
Food Sci. 37, 378-380.

Kuppuswamy, S., Srinwasan, M., and Subrahmanyan, V. 1958.
Spec. Rep. Ser. Indian Coun. Med. Res. No. 33.

Luescher, R. 1971. Evaluation of methods to determine the
sulfur containing amino acids in potatoes. Master's
Thesis, Michigan State University, East Lansing,
Michigan.

Luescher, R. 1972. Genetic variability of "available"
methionine, total protein, specific gratity and
other traits in tetraploid potatoes. Ph.D. Thesis,
Michigan State University, East Lansing, Michigan.

Metzger, C. H., Tobiska, J. W., Douglass, E., and Vail,
C. E. 1937. Some factors influencing the composi-
tion of Colorado potatoes. Amer. Soc. Hort. Sci.
Proc. 35, 635-643.

51

Morrison, F. B. 1936. Feeds and Feeding. 20th ed. The
Morrison Publishing Co., Ithaca, New York, p. 313.

Mulder, E. G., and Bakima, K. 1956. Effect of the nitrogen,
phosphorus, potassium and magnesium nutrition of
potato plants on the content of free amino acids
and on the amino acid composition of the protein of
tubers. Plant and Soil, 7, 135-165.

Murphy, H. J., and Goven, M. J. 1959. Factors affecting
the specific gravity of the white potato in Maine.
Maine Agr. Exp. Sta. Bull. No. 583, 1-24.

Nash, L. B. 1941. Relation of variety and environmental
conditions to partial composition and cooking
quality: Potato quality. IV. Amer. Potato J. 18,
91-99.

Neuberger, A., and Sanger, F. 1942. The nitrogen of the
potato. Biochem. Jour. 36, 662-671.

Rios, B. J. 1969. Protein value of potato and navy bean
powders: Nutritional evaluation using the meadow
vole (Microtus pennsylvanicus). Master Thesis,
Michigan State University, East Lansing, Michigan.

Satterthwaite, O. B. 1946. An approximate distribution of
the estimates of variance components. Biometrics 2,
110-114.

Schippers, P. A. 1968. The influence of nitrogen and
potassium application on the yield and specific
gravity of four potato varieties. Europ. Potato J.
11, 23-33.

Shaw, R., and Shuey, W. C. 1972. Production of potato
starch with low waste. Amer. Potato J. 49, 12-18.

Stucki, W. P., and Harper, A. E. 1962. Effects of altering
the ratio of indispensable to dispensable amino
acids in diets for rats. J. Nutrition. 78, 278-286.

Talley, E. A., Fitzpatrick, T. J., and Porter, W. L. 1961.
Chemical composition of potatoes. I. Preliminary
studies on the relationships between specific
gravity and the nitrogenous constituents. Jour.
Food Sci. 26, 351-355.

. 1964. Chemical composition of potatoes. IV.
Relationships of the free amino acid concentration
to specific gravity and storage time. Amer. Potato
J. 41, 357-366.

 

52

. 1970. Chemical composition of potatoes. VIII.

Effect of variety, location, and year of growth on

the content of nitrogen compounds. Amer. Potato J.
47, 231-244.

 

Watt, B. K., and Merrill, A. L. 1963. Composition of
Foods. U.S. Dep. Agr. Handbook No. 8.

Wilcox, G. E., and Hoff, J. 1970. Nitrogen fertilization
of potatoes for early summer harvest. Amer. Potato
J. 47, 99-102.

Willaman, J. J., and West, R. M. 1922. Composition of
potato tubers. Rep. Minn. Agric. Exp. Stn., p. 44.

Williams, H. H. 1959. Amino acid requirements. J. Amer.
Dietet. Assoc. 35, 929-933.

APPENDICES

APPENDIX 1

ENVIRONMENTAL DATA

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a“ camuamMuum :m

 

onfi Haamsmuh :n.mm ooN-oo~-ooH anH uHmw numpmoozu
owzo
mm mcofiuaufifinnm N :w :2 .:N .m+
nowpumahpa :m.~ mc~-NmH-NwH sacs xecam Amoccoucpso
auwwvch
«we cowuamautm 0: maum\goe pH oom+
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anmmvcm
:mcoauaacou mausotm essence: an“ oq-ow-om son xafio finance eschew
muoxan .z
macauaumfinnm NN

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ova “Housman :o.fi~ Nvm-em-NmH pcum camCOUmwz

oocomaoEo
ucmfin puma u:khv paw won: sea :ofipammnum :mH m: ukuw\nfiofi+ nanomhucmv
Hmecfiuh :m.o ~m~-~aH-NmN Ewoa chmm :achomz
meson» flouaapfia<o
gas; now macauaecou essence; so” afiauapau :NH o-cNH-oNa amoa acumm «snappoz

:oprho>mw: “pom

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gm“: ”oucowuoEo pagan oumH mmH o--ww-on Ema” uHmm Aswaxcuum 362V
“unemmwz

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fiewaom couamv
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umo>uag hmogucm Hauouv
on mewucuan camummwuum oNx.moN

uoguo scam man: can "Hamcmmm ouuuxna honmamuaom Hwow namuauog

«paw Hmucosq0hw>cu "H xfipcomm<

53

APPENDIX 2

TOTAL PROTEIN, "AVAILABLE" METHIONINE, BIOLOGICAL
VALUE, RELATIVE PROTEIN QUALITY AND TOTAL DRY
MATTER DATA OF 16 VARIETIES GROWN IN

10 LOCATIONS IN 1971

TOTAL PROTEIN,

Legend:

total protein
"available" methionine

biological value

relative protein quality

total dry matter

Variety

VALUE,

\IO‘U‘DWNH

"AVAILABLE"

54

APPENDIX 2

METHIONINE, BIOLOGICAL

RELATIVE PROTEIN QUALITY AND TOTAL DRY
MATTER DATA OF 16 VARIETIES GROWN IN

10 LOCATIONS IN 1971

mg (Nx6.25)/100 mg dry matter
mg available met/16mg N

growth produced by 50 mg
potato protein as a percent-
age of growth produced by 50
mg casein

the reciprocal of the per-
centage increase in growth as
a result of supplementing all
essential amino acids except
methionine

dry matter/100 9 whole potato
calculated from specific
gravity where specific
gravity is determined by;

(wt. in air)/(wt. in air -
wt. in water)

86024-3
36097-9
86139-11
86116-18
Cobbler

La 22-111
Neb 1.57-1

8

9
10
11
12
13
14
15
16

Location A

LIHIEQ'UMUOED

55

: N49.62-5

N 93.55-16
Norland
ND6925-13
ND6993-13
ND7196-18
Red Pontiac

: W 629
: W 634

Louisiana

Kansas

Missouri

Nebraska

Michigan

Wisconsin

North Dakota
Indiana sandy loam
Indiana muck

Ohio

13

Aver.

J

56

L 0 C A T I 0 N
”Availabl€ Methionine

A

F

 

1.79

1.87

1.78

1.61

1.93

1.77

 

1.89

1.75

1.65

1.69

2.41

1.62

1.51

 

1.78

1.64

2.01

1.58

1.74

1.47

 

1.87

1.76

1.79

1.68

1.43

1.62

1.66

1.48

 

2.04

1.80

1.69

1.59

1.48

1.51

1.56

1.22

 

1.57

1.74

1.74

1.70

1.39

1.50

1.47

1.43

 

1.71

1.68

1.68

1.44

1.51

1.49

1.24

 

1.89

1.59

1.60

1.17

 

1.63

1.96

1.71

1.48

1.58

1.52

1.43

1.49

1.23

 

1.84

1.66

1.49

1.52

1.40

1.74

1.44

1.21

1.35

 

1.65

1.61

1.56

1.25

1.51

1.34

1.19

1.29

1.22

 

1.66

1.57

1.40

1.43

1.34

1.22

1.29

1.37

1.22

1.10

 

1.39

1.48

1.35

1.39

1.27

1.24

.99

1.25

.96

 

1.66

1.29

1.40

1.22

1.21

1.16

1.04

Aver.

1.71

1.64

1.63

1.63

1.61

1.55

1.55

1.41

1.36

1.27

1.25

 

1.46

1.23

1.43

1.18

1.18

1.08

.99

1.23

 

 

1.38

 

 

1.36

1.13

 

 

 

 

1:66

1T5?

“ii—55‘

 

1.14

 

.94

 

1.24

 

1.01

1.16

 

 

1.38

1.38

1.35

1.20

Total protein

10

15

11

14

12

16

13

L"!

Aver.

E

J

H

57

L 0 C A T I 0 N

C

H

A

D

G

 

16.6

17.2

15.0

13.9

12.0

14.3

11.8

15.2

11.5

12.6

 

15.3

16.5

14.6

13.9

13.7

13.7

13.6

13.5

13.7

10.6

 

16.4

18.0

14.2

13.6

9.4

13.0

13.7

12.8

13.2

11.9

Aver.

14.0

13.9

13.6

 

15.3

15.1

13.7

13.4

13.3

13.9

13.4

13.8

11.4

10.5

13.4

 

14.1

14.5

14.7

13.5

15.3

11.6

14.0

11.0

11.2

13.3

 

14.8

15.0

13.9

12.3

12.4

12.2

11.7

13.4

12.4

13.1

 

17.7

16.3

13.3

12.4

14.5

11.5

11.6

11.3

10.3

11.5

13.1

 

14.6

13.6

13.4

13.8

13.7

13.1

11.8

10.9

11.8

10.6

12.7

 

14.6

15.7

14.0

12.8

12.4

10.9

12.7

11.2

10.3

12.5

12.7

 

15.6

12.5

12.2

13.5

13.2

12.0

11.7

12.5

11.5

10.1

12.7

 

14.1

02.5

12.2

12.3

13.2

13.2

13.2

10.1

11.8

10.1

12.3

 

16.2

14.0

1.6

11.3

13.6

11.6

10.8

12.0

9.2

9.6

12.0

 

12.7

13.5

11.9

13.5

11.9

12.0

9.2

10.1

11.5

 

13.3

12.9

12.0

11.3

12.0

12.3

10.6

10.5

10.1

11.5

 

12.2

13.0

12.3

10.9

11.1

11.3

9.8

10.9

10.7

11.2

 

12.9

 

 

10.6

 

 

11.8

 

 

10.5

 

 

9.1

 

 

10.9

 

 

14.8

14.8 13.3 12.8 12.6

12.5 12.0 11.9 11.1 10.9

8V

0'!

14

11

10

15

16

12

13

Aver.

58

L 0 C A T I 0 N

I

J

C

E

 

81.0

78.1

77.0

77.4

71.9

71.2

69.6

70.0

68.7

69.3

 

75.2

71.5

72.8

74.5

73.3

77.6

71.5

67.9

69.2

65.6

 

71.8

72.5

74.6

74.0

72.6

71.8

63.6

70.0

68.6

 

 

homo

74.3

73.1

74.1

71.2

73.2

67.0

68.0

67.3

 

76.4

L4.

69.1

68.2

68.7

66.9

66.5

67.9

67.3

64.5

 

78.5

67.9

72.8

73.1

74.4

70.8

69.7

67.9

65.0

61.4

 

71.8

73.6

68.6

72.6

65.6

 

73.8

71.5

72.1

71.2

72.9

65.4

64.1

68.3

70.7

64.5

 

75.2

66.8

68.4

70.3

67.9

69.0

73.3

65.7

70.2

67.3

 

70.3

69.0

67.3

70.0

73.3

71.8

68.1

69.6

66.4

62.4

 

70.3

69.4

71.4

69.7

72.6

67.6

64.0

66.6

61.1

 

78.2

84.6

71.8

69.0

64.4

68.3

63.7

67.5

58.3

Aver.

73.3

71.8

71.5

71.3

70.9

70.1

70.1

69.4

69.3

68.7

68.6

68.4

 

73.1

69.2

71.5

67.3

64.4

73.3

66.5

68.2

64.0

66.9

68.3

 

76.7

70.6

66.9

68.7

71.3

68.3

65.1

66.8

61.4

 

65.8

67.5

65.6

71.8

70.1

65.1

66.6

62.3

61.1

 

 

69.8

61.9

 

69.4

 

 

64.8

 

65.8

 

59.3

 

63.3

62.2

 

61.5

 

54.8

 

 

 

74.8 72.3 70.9

70.8

70.5

69.6

68.0 66.5 66.4 63.7

Relative

13
15
7
8
5

V
9

A
1

R
10

I
3

E
14

T
2

Y
16
6
11
12
4
Aver.

protein quality

59

L 0 C A T I 0 N

A

H

G

B

 

.578

.503

.483

.498

.524

.524

.490

.483

.441

.413

Aver.

.494

 

.575

.459

.529

.500

.465

.541

.483

.452

.444

.452

 

.515

.526

.505

.483

.472

.498

.478

.472

.488

.452

 

.549

.472

.478

.500

.472

.442

.457

.474

.424

.365

 

.521

.483

.498

.467

.478

.444

.457

.450

.420

.403

 

.546

.508

.503

.455

.442

.465

.472

.427

.427

.356

 

.526

.478

.476

.493

.461

.442

.424

.442

.364

 

.498

.474

.485

.459

.476

.444

.455

.392

.392

.364

 

.543

.457

.441

.418

.356

 

.532

.478

.442

.433

.439

.433

.420

.435

.407

.365

 

.493

.461

.461

.444

.402

.391

.412

.437

.388

 

.529

.461

.435

.446

.418

.439

.410

.412

.388

.375

 

.535

.457

.452

.441

.442

.431

.405

.403

.382

.348

 

.478

.433

.476

.452

.444

.408

.413

.388

.405

.336

 

.427

.483

.410

.444

.478

.418

.397

.391

.420

.355

 

 

.495

.448

 

 

.444

 

 

.422

.379

 

 

.415

 

.364

 

.397

 

.378

.490

.489

.463

.462

.460

.456

.444

.443

.438

.432

.431

.430

.423

.422

 

 

.521

.473

.472

.465

.459

.449

.438

.425

.421

.379

Total dry matter

16

12

15

13

11

10

14

Aver.

G

F

D

60

L 0 C A I I 0 N

J

C

B

E

H

 

19.4

21.4

19.7

18.8

22.4

 

24.8

20.3

18.0

20.3

19.7

27.8

19.2

18.0

17.7

17.5

 

23.3

22.2

19.7

20.5

18.2

18.2

20.3

19.1

19.7

 

23.5

20.7

21.4

19.7

18.0

19.7

19.0

17.3

20.3

18.8

 

23.1

22.4

19.7

19.2

18.8

18.8

19.2

19.2

19.9

17.1

 

24.6

22.9

20.7

19.0

18.4

16.7

18.4

19.2

18.0

16.7

 

24.2

19.9

19.9

18.0

20.3

18.6

18.4

18.2

18.0

17.7

 

24.2

22.2

20.7

18.8

19.4

16.9

18.2

18.4

17.1

16.9

 

22.7

19.4

20.1

19.4

19.0

17.5

18.0

16.2

17.3

 

22.0

20.3

20.7

18.8

17.1

18.2

18.4

16.0

18.6

16.2

 

23.1

20.1

19.7

18.4

16.9

17.5

16.9

17.5

16.9

17.1

 

23.1

18.8

18.8

18.4

17.3

17.1

17.3

17.1

17.1

17.1

Aver.

20.3

20.3

20.0

19.8

19.7

19.5

19.3

19.3

18.7

18.6

18.4

18.2

 

20.9

17.5

18.6

16.7

16.5

15.0

0

15.

16.9

17.1

13.9

 

19.9

18.8

22.0

18.2

14.3

13.7

16.2

14.3

15.4

16.8

16.3

 

20.7

18.2

16.9

15.4

16.5

16.7

11.4

 

 

 

 

 

 

14.1

15.0

 

 

r-rj‘

 

15.6

 

 

L1‘7.B'JL17.3"L'1"'7.5 17.1 '

16.5

16.1

 

APPENDIX 3

TOTAL PROTEIN, "AVAILABLE" METHIONINE, BIOLOGICAL
VALUE, RELATIVE PROTEIN QUALITY AND TOTAL DRY
MATTER DATA OF 8 VARIETIES IN 4 REPLICATIONS

GROWN IN MICHIGAN IN 1972

TOTAL PROTEIN,

APPENDIX 3

"AVAILABLE" METHIONINE, BIOLOGICAL

VALUE, RELATIVE PROTEIN QUALITY AND TOTAL DRY

MATTER DATA OF 8 VARIETIES IN 4 REPLICATIONS

V A R I E T Y

"Available" methionine
Rep 2 5 7
1 1.95 1.58 1.40
2 2.00 1.75 1.30
3 1.98 1.75 1.25
4 1.98 1.60 1.30
Relative protein quality
1 .385 .461 .441
2 .379 .425 .459
3 .390 .431 .461
4 .420 .446 .455
Biological value

1 72.5 76.1 68.1
2 72.5 75.4 67.4
3 73.9 76.1 65.9
4 76.1 74.6 66.7
Total protein

1 13.0 14.9 15.3
2 13.3 13.0 16.6
3 11.8 13.4 16.0
4 12.5 13.8 15.8
Dry matter

1 19.7 17.5 18.0
2 18.2 18.4 16.7
3 20.1 18.2 16.9
4 19.7 18.0 17.5

10

1.88
1.73
1.80
1.55

.385
.397
.389
.392

70.3
68.8
69.6
64.5

15.8
15.9
16.7
16.5

19.0
16.0
15.4
14.8

61

11

1.95
1.93
1.75
1.88

.351
.357
.392
.372

65.9
66.7
68.8
68.1

14.8
15.1
15.6
14.7

17.3
17.3
16.7
18.2

GROWN IN MICHIGAN IN 1972

13

1.13
1.20
1.35
1.13

.493
.439
.441
.459

66.7
61.6
65.9
62.3

14.9
13.1
13.8
12.6

16.7
18.6
16.7
18.0

14

2.05
1.90
2.03
1.95

.361
.388
.364
.366

70.3
71.7
70.3
68.8

13.3
14.2
12.4
12.7

17.3
17.7
18.4
17.7

15

1.25
1.18
1.23
1.33

.441
.465
.444
.444

63.0
64.5
63.0
66.7

16.2
15.3
17.4
14.9

17.7
17.1
16.5
17.5

APPENDIX 4

ANALYSIS OF VARIANCE FOR AVAILABLE METHIONINE,
RELATIVE PROTEIN QUALITY, BIOLOGICAL VALUE,

TOTAL PROTEIN AND TOTAL DRY MATTER

APPENDIX 4
ANALYSIS OF VARIANCE FOR AVAILABLE METHIONINE,
RELATIVE PROTEIN QUALITY, BIOLOGICAL VALUE,

TOTAL PROTEIN AND TOTAL DRY MATTER

 

Legend:

L : locations

V : variety

VxL : variety-location interaction

R(L) : replicationwithin location

RxV(L) : replication-variety interaction within location
Source df SS MS FS

L 9 2929.38 325.49 28.11**
V 15 4242.11 282.81 17.59***
VxL 127 2042.25 16.08 2.88**
R 3 16.75 5.58 ns
RxV(L) 21 164.53 7.83

Relative protein quality

L 9 2070.76 230.08 605.49***
v 15 903.82 60.25 12.91***
VxL 127 592.68 4.67 1.73 ns
R(L) 3 1.66 .55 ns
VxR(L) 21 56.62 2.70

62

63

 

Source df SS MS FS
Biological
L 9 1360.09 151.12 18.53***
V 15 886.45 59.10 4.72***
VxL 127 1589.26 12.51 3.86***
R(L) 3 3.19 1.06 ns
VxR(L) 21 68.11 3.24
Total protein
L 9 2525.72 280.64 27.17*
V 15 1265.46 84.36 7.10***
VxL 127 1509.99 11.89 2.06*
R(L) 3 14.98 4.98 ns
VxR(L) 21 120.96 5.76
Total dry matter
L 9 4143.30 460.37 12.46***
V 15 2871.39 191.43 10.30***
VxL 127 2359.22 18.58 2.16*
R(L) 3 13.00 4.33 ns
VxR(L) 21 181.00 8.62
* : significant at P = .05.
** : significant at P = .01.
*** : significant at P = .001.

APPENDIX 5

AMOUNTS OF ADDED COMPONENTS PER 1 kg

OF POTATO AND CASEIN DIETS

APPENDIX 5
AMOUNTS OF ADDED COMPONENTS PER 1 kg

0F POTATO AND CASEIN DIETS

 

 

 

Grams in
Sample Grams Added Composition

Whole Flour 687.0

Protein 90.0 9.0
Fat 5.5 74.5 8.0
Salts 25.4 24.6 5.0
Vit. . . 10.0 1.0
Cellulose 11.0 1.1
Water 48.1 1.9 5.0
Starch 507.0 50.7
Sucrose 202.0 20.2
Concentrate Flour 273.3

Protein 90.0 9.0
Fat 2.2 77.8 8.0
Salts 10.1 39.9 5.0
Vit. 10.0 1.0
Cellulose 14.3 1.4
Water 13.7 36.3 5.0
Starch 143.0 364.0 50.7
Sucrose 198.7 19.9
Casein 103.4

Protein 90.0 9.0
Fat 1.2 78.8 8.0
Salts .7 49.3 5.0
Vit. 10.0 1.0
Cellulose 10.0 1.0
Water 9.9 40.1 5.0
Starch 507.0 50.7
Sucrose 201.4 20.1

64

APPENDIX 6

PROTEIN CONSUMPTION, WEIGHT GAIN, NIE, AND

PERCENT BODY PROTEIN DATA OF RAT ASSAY

APPENDIX 6

PROTEIN CONSUMPTION, WEIGHT GAIN, NIE, AND

PERCENT BODY PROTEIN DATA OF RAT ASSAY

Protein Weight 8 Body
Diet NIE consumed(g) gain(g) protein
Whole potato .358 32.5 73.5 16.20
flour .464 34.3 83.5 17.90
” .436 35.3 87.5 16.74
" .362 35.6 74.5 16.66
" .428 29.3 63.0 17.26
" .488 27.9 76.0 17.64
" .444 29.9 69.5 17.52
" .476 38.4 99.0 16.64
" .424 27.5 59.0 22.10
.480 29.1 64.5 17.88
Concentrate .404 37.7 85.0 17.26
" .456 29.3 67.5 18.32
” .454 27.5 61.0 17.66
” .418 30.8 71.0 17.16
" .354 31.4 63.0 17.04
" .404 29.5 65.5 17.04
" .498 25.3 60.0 18.16
" .444 31.7 65.0 17.94
" .428 31.4 65.0 18.06
" .476 39.2 94.0 17.90
Casein .572 30.9 90.0 18.38
" .580 30.8 95.0 17.96
" .535 35.1 105.0 17.86
" .648 35.9 117.5 18.08
" .602 40.2 132.5 17.18
" .546 36.1 97.5 18.88
" .554 36.3 99.0 18.48
" .566 35.5 102.5 17.86
” .608 40.7 123.5 18.22
" .622 31.4 103.0 18.08

65

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