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III. Milling and Baking Research Laboratories

III. Milling and Baking Research Laboratories

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Year



Market class



TABLE I

Establishment of Laboratories Engaged in Wheat Quality Research

Department, institution, or organization



1923

1931

1932

1933

1936

1937



Hard red spring

Hard red spring

Hard red spring

Soft red winter

Hard red winter

White winter and spring

Hard red winter and spring

Hard red spring

Hard red spring and winter

Hard red spring, hard and soft

red winter, soft white, durum

Hard red winter

Soft red winter

Durum

Durum

Soft red winter

Hard red winter



1938

1941

1942

1946



Durum

Soft red winter

Soft red and white

White winter and spring



1954

1956

1959

1961

1961



Hard

Hard

Hard

Hard

Hard



1897

1906

1908

1910

1911

1911

1913

1913

1918

1918



red winter

red spring and winter

red winter

red winter

red spring, durum



Location



Agronomy, Agr. Expt. Sta.

Cereal Crops, Central Expt. Farm

Chemistry, Agr. Expt. Sta.

Agronomy, Agr. Expt. Sta.

Chemistry, Agr. Expt. Sta.

Chemistry, Agr. Expt. Sta.

Agronomy, Agr. Expt. Sta.

Grain Res. Lab., Board of Grain Commissioners

Aroostook Farm, Agr. Expt. Sta.

Bur. Agr. Econ. and Bur. Plant Ind., U.S.D.A.



St. Paul, Minnesota

Ottawa, Canada

Fargo, North Dakota

Wooster, Ohio

Manhattan, Kansas

Pullman, Washington

Bozeman, Montana

Winnipeg, Canada

Presque Isle, Maine

Washington, D. C.



Agr. Chemistry, Agr. Expt. Sta.

Agronomy, Agr. Expt. Sta.

Bur. Agr. Econ. and Bur. Plant Ind., U.S.D.A.

Grain Res. Lab., Board of Grain Commissioners

Bur. Plant Ind., U.S.D.A. and Agr. Expt. Sta.

Bur. Plant Ind., U.S.D.A. and Milling Industry,

Agr. Expt. Sta.

Cereal Technology, Agr. Expt. Sta.

Home Economics, Agr. Expt. Sta.

Cereal Crops, Central Expt. Farm

Bur. Plant Ind., U.S.D.A. and Agr. Chemistry,

Agr. Expt. Sta.

Biochemistry, Agr. Expt. Sta.

Agronomy and Soils, Agr. Expt. Sta.

Agronomy, Agr. Expt. Sta.

Agr. Chemistry, Agr. Expt. Sta.

Cereal Technology & Crops Res., Agr. Expt. Sta.



Lincoln, Nebraska

West Lafayette, Indiana

Washington, D. C.

Winnipeg, Canada

Wooster, Ohio

Manhattan, Kansas

Fargo, North Dakota

Columbus, Missouri

Ottawa, Canada

Pullman, Washington

Stillwater, Oklahoma

Bozeman, Montana

Lincoln, Nebraska

Aberdeen, Idaho

Fargo, North Dakota



90



ERHARDT R. HEHN AND MARK A. BARMORE



The rediscovery of Mendel’s laws of genetics and their application

to plant breeding gave impetus to wheat improvement by hybridization.

Secure in the knowledge of genetic laws, the plant breeder was confident that he could select with considerable objectivity from his crosses

progeny agronomically superior. The breeder was equally certain that

he could not objectively classify his progeny on the basis of external

appearance for those internal kernel characteristics determining milling

and baking properties. To be effective in breeding for quality improvement, rapidly conducted direct and indirect tests were necessary.

These and other needs and questions motivated the establishment

of federal and state research laboratories dedicated to the search for

basic knowledge, evaluation of plant breeding material, and service to

industry. The laboratories established between 1897 and 1961 are listed

in Table I.

IV. Microquality Flour Tests



The early American, water wheel-powered flour mill was a purely

local enterprise. It served a trade territory within wagon distance of the

mill. Quality control was not of particular concern to the miller. His

job was to grind the wheat and sift the flour. It was the housewife who

made the necessary adjustments in her baking procedure to the differences in quality among the flour lots.

Industrialization and centralization of the milling industry resulted in

the milling of wheats originating over a wide geographic area and created need for flour markets national and international in scope. Quality

control now became a function of the miller. To maintain a consumeracceptable level of flour standardization, it became necessary to evaluate not only the flour, but the wheat shipments prior to milling. To

achieve this end, quality control laboratories staffed by chemists were

established in commercial mills. These cereal chemists were not faced

with a supply problem; therefore, they developed laboratory quality

tests and designed laboratory mills without any serious concern for

sample size. Their answer to a highly repeatable laboratory quality test

was the one-pound loaf. A laboratory mill which required five pounds

of wheat satisfied the requirements of adequately simulating milling

steps in the large commercial mill and supplying sufficient flour for the

baking of several one-pound loaves.

When the state and federal quality research laboratories were established, it was soon realized that the commercial quality laboratory

methods did not completely meet their needs. In contrast to large relatively homogeneous commercial lots in industry, research cereal chemists found themselves dealing with large numbers of small samples from



91



BREEDING WHEAT QUALITY



varieties and selections grown in plant breeder yield nurseries. The

standard, rod-row yield nursery rarely provided enough seed of any

single entry to meet the needs of a commercial laboratory test. To meet

the sample-size limitations, the quality laboratory tests were scaled down

to a 100-g. grain requirement. Reduction in sample size did reduce the

accuracy of the quality tests, but this was more than compensated for

by an increase in the number and type of research samples lending

themselves to test. The need of plant breeders for quality evaluation

methods requiring a sample size no larger than can be obtained from a

single wheat plant remained unsatisfied.

The evaluation of any grain sample, however large or small, on the

basis of the quality of the end product-be it a loaf of bread, cake, or

string of spaghetti-is in any event a laborious process. Laboratory

control chemists, research chemists, and plant breeders have all engaged

in either the miniaturization of standard laboratory tests or the adaptation of microquality tests to the smallest possible sample size.

TABLE I1

Quality Characteristics of Bread, Pastry, and Macaroni Flour

Measurable by Micromethods

Characteristic



Bread



Pastry



Macaroni



Protein content ( 7 0 )

Flour yield

Ash

Flour color

Sedimentation

Flour absorption

Mixing properties

Loaf volume

Viscosity

Cookie diameter



11-13

High

Low

White

High

High

Strong

Large

High

Large



7-9

High

Low

White

Low

Low

Very weak

Small

Low

Small



11.5-13

High

Medium

Light yellow



-



Low

Medium to weak

Small



-



In the following subsections, development of the microquality tests

applicable to bread, pastry, and durum flour evaluation, for which

varietal differences have been demonstrated and which have been investigated and used by plant breeders as selection tools, are briefly described. The quality characteristics of bread, pastry, and macaroni measurable by micromethods are given in Table 11.



A. LOAFVOLUME

Geddes and Aitken (1935) made comparative bakes of 25 g. of flour,

milled on a scaled-down Allis-Chalmers mill, with 100-g. bakes. The

correlation coefficient between the loaf volume of the 100-g. loaf and

the 25-g. loaf was a significant 0.982. Correlation coefficients of similar



92



ERHARDT R. HEHN AND MARK A. BARMORE



magnitude were reported for crude protein per cent, carotene parts per

million, and diastatic activity. The investigators suggested that the reported micro baking method was applicable to the evaluation of Fs and

later generations.

A complete series of small-scale baking equipment designed for a

baking test of 100 g. of wheat was described by Shogren and Shellenberger (1954). According to Van Scoyk ( 1939) stimulation of interest

in the potential value of 25-g. flour doughs can be credited to Werner

(1925), who did not consider gluten quality to be a reliable indicator of

baking quality.

Using micro milling and baking techniques, Shellenberger and associates (1958) were able to obtain information (reported in the accompanying tabulation ) from 300 plant breeder samples from Texas,

Oklahoma, Kansas, and Nebraska using 100-g. wheat samples.

Grain

1,000 Kernel weight

Protein

Ash

Moisture



Flour

Yield

Protein

Ash

Moisture



Baking

Farinograph absorption

Mixing tolerance index

Mixing time

Loaf volume



The loaf volume correlation coefficient between the standard laboratory bake and 10-g. bake was 0.86. The method was recommended

for early generation, small plot, and greenhouse evaluation.

Volume of the micro-loaf is not widely used by plant breeders as

a criterion of quality in the bread wheat breeding programs because it

lacks the essential features of simplicity and rapidity.

B. RECORDINGDOUGHMIXERS

The artistry of baking has centered on the ability of the artisan to

predict the quality of the finished product from the feel of the dough.

Such terms as bucky, stiff, sticky, silky, smooth, and dead occur in the

vernacular of the miller and baker. These terms are descriptive of physical properties of a dough amenable to objective measurement. Efforts

in this direction resulted in various instruments designed to measure the

power input pattern of a continuously agitated flour-water system.

C. W. Brabender (1934) reported to the American Association of

Cereal Chemists six years of experience in Germany with a continuous

recording dough mixer, the farinograph, developed in his laboratory.

Based on the principle of a dynamometer, this instrument records the

properties of a dough being agitated by two synchronized screw blades.

The farinograph power input curve, farinogram, inscribed by the continuous recorder measures the point of maximum dough consistency re-



93



BREEDING WHEAT QUALITY



ferred to either as peak or mixing time (Fig. 1 ) . The acute angle of

declination of the curve following the peak is interpreted as a measure

of dough tolerance to a wide range of dough mixing time schedules in

the commercial bake shop. It was optimistically anticipated that information from the farinograph would be superior to the protein test as a

prediction of loaf volume in the hard red wheats and pastry quality in the

soft red and white wheats. Numerous investigations, as exemplified by the

work of Geddes et al. (1940), have established that farinogram characteristics are in general associated with protein content and are equally

inconsistent in their relationship to loaf volume. This lack of loaf volume



4

-



FARINOGRAMS



t



I

e

B



E



s

MIXOGRAMS



Y



K



I !

MIXING TIME



I

.---C



FIG. 1. Typical farinograms and mixograms of strong and weak flours as recorded



by the farinograph and mixograph.



relationship, however, does not detract from the instrument’s objective

characterization of dough handling properties so important in the automated bakery.

The National-Swanson-Working recording mixer was developed in

the United States (Swanson and Working, 1933). It is known as the

mixograph and differs essentially from the farinograph in the manner

of dough mixing. The water-flour system is agitated by a system of stationary and planetary moving pins. The record of power input over time

is similar to the farinogram and is called a mixogram (Fig. 1).Swanson

and Johnson (1943) described five measurements that can be made on

the mixograph curve (Fig. 1 ) : (1)degree of incline; (2) time to reach

maximum height; ( 3 ) magnitude of height; ( 4 ) degree of decline or

weakening angle; (5) incline plus decline angle. Height of the curve

was found to be determined by protein and moisture content. A large

incline plus decline angle sum indicated a wide range in the mixing

tolerance of a dough. A. J. Johnson et al. (1943), using two dough



94



ERHARDT R. HEHN AND MARK A. BARMORE



formulas, concluded that the height, width, and weakening angle of the

mixogram were positively correlated with loaf volume and protein content.

The partial correlation coefficient between loaf volume and weakening angle, holding protein content constant, was negative and significant. The mixogram curves tended to differ among the twelve varieties of hard red wheat tested. In two series of hard red spring wheat

varieties grown at four locations in two years, Harris et al. (1944)

found significant mixogram characteristic variances due to years, stations, and varieties. In general, the variety x station interactions were

not significant. The authors were confident that the mixograph served

as an accessory tool in the evaluation of hard red spring wheat varieties

and selections.

Morris et al. (1944) investigated the relationship of the total area

under the mixograph curve as a measure of soft red wheat quality.

Mixogram area exhibited a significant negative association with cookie

spread. Flour protein was not as highly correlated with loaf volume

and cookie spread as was the mixogram area in a series of 29 varieties.

Lamb (1944) described a method of preparing 125 g. of sifted wheat

meal for mixogram evaluation. He found a correlation coefficient of 0.90

between the mixogram area of rapidly prepared meal and standard laboratory mill flour samples demonstrating that time-consuming sample

milling was unnecessary.

Recording dough mixers have been shown to provide an objective

measurement of physical dough properties not always reflected by protein content nor related to loaf volume. The farinograph has become a

standard item of equipment in the quality control laboratories of commercial mills. Proper interpretation of the farinograph curve pattern

provides the cereal chemist and plant breeder with an indication of

the performance of flour under exacting production schedules and dough

machinability requirements of an automated bake shop. Bakers commonly include mixing time and mixing tolerance specifications in their

flour orders, Farinograms are in common use by plant breeders in

evaluating advanced selections. The mixogram has not found widespread

acceptance in the trade, but is used as a measure of quality in plant

breeding programs. Finney (1963) has concluded it is one of the most

reliable indicators of quality of bread wheats for use with 100-200 g.

samples.

C. WHEATMEAL FERMENTATION

TIME

Recording dough mixers do not meet the need of plant breeders for

selection criteria that can be applied on a single-plant basis or short

line rows. This need for micromethods that can be rapidly applied to a



BREEDING WHEAT QUALITY



95



large number of individual plant samples is expressed by Cutler and

Worzella ( 1931 ) : “For years the plant breeder has hoped in vain that

the cereal chemist would develop and perfect some test whereby an

accurate indication of quality of wheat could be obtained from a few

grains of wheat.” In response to this plea, Cutler and Worzella adapted

the Saunders test from flour to the use of 10 g. of meal, which was

formed into a ball of dough by the addition of a yeast solution and distilled water. The hand-kneaded doughball was placed in a beaker of

water maintained at a constant temperature. Time was recorded in minutes as the interval between immersion of the doughball in water and

definite evidence of doughball disintegration. Positive correlations were

reported between fermentation time and protein content, absorption,

loaf volume, and vitreous kernels for a large number of samples representative of the hard red, soft red, and soft white classes grown in the

established areas of production. In 1933, the same investigators (Cutler

and Worzella, 1933) obtained equally promising results from the use

of 3 . 5 5 g. whole wheat meal. An interannual fermentation time correlation coefficient of 0.671 for 67 hybrid selections from F, families was

interpreted as evidence of a genetic basis for fermentation time differences among the selections.

Pelshenke (1933) justified this simple test on the basis of two general

factors determining the baking quality of wheat: ( 1 ) those that cause

the gas holding power of dough; ( 2 ) those that influence the gas production of dough.

Many breeders and chemists have investigated the efficacy of the

wheat meal fermentation time test as an indicator of quality with varying degrees of success, from complete rejection by Bird (1957) to enthusiastic acceptance. Supplementation of the dough formula with sugar

and elemental yeast food has been used as a means of eliminating gassing power as a factor in fermentation time. This supplementation can

be justified because it is a dough modification practiced by millers and

bakers. Bayfield (1935) has attributed some of the unsatisfactory results to a sticking of some spreading types of doughballs to the sides

of the beakers, human error in the hand preparation of the dough, and

lack of a precise point of disintegration.



D. EXPANSION

Interest in development of a simple test of quality based upon the

swelling and water-imbibing properties of gluten has challenged cereal

chemists and plant breeders for decades. Hays and Boss (1899) suggested the use of the “bakers’ sponge test” as an aid in discarding less

desirable varieties of wheat. This test was a simple measure of volume



96



ERHARDT R. HEHN AND MARK A. BARMORE



increase of a definite quantity of fermenting dough. A dough expansion

test using a 5-g. flour doughball was reported by Miller et a2. (1951).

The yeast-leavened doughball supplemented with yeast food and sugar

was placed in a large-mouth jar filled with a weak saline solution. The

jar lid was equipped with a length of 10-mm. glass tubing graduated in

milliliters. Dough expansion was recorded at the point of maximum rise

of the water in the glass tubing. The doughball expansion test was found

to be equal to protein content in predicting the loaf volume of hard red

spring wheat samples of similar protein quality. In samples exhibiting

digerences in protein quality, as might be expected in breeder samples

representing selections from highly divergent parents, the expansion test

was superior to the protein test as an indicator of potential loaf volume.

Harris and Sibbitt (1956) obtained similar results in correlating the

expansion test with loaf volume data of 50 hard red spring wheat selections derived from the North Dakota breeding program and 55 selections

from Mexico representing a wide range of quality in the parental background, which supported the observations of Miller and associates. The

correlation coefficient between the expansion volume and loaf volume

of the North Dakota breeder samples was 0.101, indicating a negligible

difference in protein quality of the hybrid parents. In contrast to the

North Dakota selections, the diversity of quality in the parentage of

the Mexican selections reflected in the progeny a significant correlation

coefficient of 0.601. These investigators were of the opinion that expansion volume was also indicative of flour absorption, mixing requirements and dough handling properties.



E. SEDIMENTATION

This most recently developed microtest for quality is based on the

hydration capacity of flour in a weak acid suspension. Flour hydration

was intensively studied by Sharp and Gortner (1923) by means of viscosity measurements. Viscosity measurements have been extensively used

as an index of soft red wheat flour strength. Finney and Yamazaki

(1946a) measured the water retention capacity of 5 g. of flour in a

weak lactic acid solution against centrifugal force. The supernatant was

decanted, and the weight difference between the hydrated flour and

initial weight was used as a measure of quality. The hydration values

of hard red winter wheat samples grown in Great Plains nurseries were

associated with protein content and loaf volume. The significance of

standard partial regression of loaf volume on water retention independent

of protein and variation in regression coefficient values among varieties

were considered as evidence of the ability of this method to measure

protein quality differences.



BREEDING WHEAT QUALITY



97



Capitalizing on the swelling property of hydrated flour, Zeleny (1947)

developed a simple test for the measurement of water-retention capacity

of flour. The method consisted of the gentle mixing of a 5-g. flour sample

and a weak lactic acid solution in a stoppered graduated cylinder. After

a 5-minute rest period the sharp line of sediment was read directly on

the graduated cylinder. Protein content, sedimentation values, and loafvolume determinations made on 135 samples of hard red winter wheat

were interrelated as indicated by significant correlation coefficients. Evidence of a measure of quality independent of protein quantity was provided by a significant partial correlation coefficient of loaf volume on

sedimentation at a constant protein level. Similar data supporting the

usefulness of the sedimentation test as a microtest for quality indication

is presented by Pinckney et al. (1957). Zeleny et al. (1960) reported

favorably on the value of the sedimentation test in screening F3 lines

for mixing tolerance. Significant positive correlations were obtained between sedimentation value and mixogram measurements indicative of

mixing tolerance. Gillis and Sibbitt (1963) were not as enthusiastic

over the usefulness of the sedimentation values as a measure of quality

in breeder samples. From the viewpoint of the plant breeder, Dewey

(1963) found the sedimentation test a useful tool in classifying hard

red winter selections for mixing stability and loaf volume.



F. PEARLING

INDEX

Degree of kernel hardness is the quality referred to by the adjectives,

soft and hard, used in naming certain market classes of wheat. Hardness

of kernel is considered desirable in the hard red and durum classes and

conversely in the soft red and white classes. The common laboratory

method of determining kernel hardness is to subject a given quantity

of wheat to the abrasive action of a grinding stone for a specified period

of time and calculating the percentage grain weight loss (Taylor et al.,

1939). A standard laboratory barley pearler is used to determine this

characteristic, and the weight loss has been called the pearling index.

Taylor and his associates found a strong correlation between pearling

index and flour particle size in a series of soft and hard red winter wheat

varieties. Protein content was not associated with pearling index. Cutler

and Worzella ( 1931) reported strong interannual correlations for kernel

hardness in varieties of wheat grown throughout the United States and

Canada. Beard and Poehlman (1954) concluded from F2 and F5 data

that the genetic variability of pearling index was large relative to the

environmental effects.



98



ERHARDT R . HEHN AND MARK A. BARMORE



G. VISCOSITY

Another small-scale test dependent on the properties of flour which

appear to be similar to those expressed by sedimentation is the viscosity

test. It requires 20 g. of flour in 100 ml. of water to which 6 ml. of normal

lactic acid is added, followed by agitation and measurement of viscosity.

The instrument commonly used is the MacMichael viscosimeter, which

consists of a disk-shaped bob suspended by a fine wire in a rotating

cup of the flour suspension. The viscosity is expressed in degree of twist

imparted to the bob. The test has been widely used in the production

of pastry and cracker flours and in the quality evaluation of soft wheats

(Barmore, 1958, 1959; Bode, 1959) ever since Sharp and Gortner ( 1923)

published their extensive study. However, there is some doubt as to the

significance of the results of this test in terms of soft wheat baking

quality, because the acidification of flour causes a swelling of proteins

which appears to affect the viscosity out of proportion to protein’s apparent importance in cookie baking (Yamazaki, 1962).

H. COOKIEBAKING

Yamazaki (1962) considered the cookie baking test to be the most

reliable index of soft wheat quality. The amount of flour required was

reduced from 225 g. to 40 g. by Finney et al. ( 1950). Their micromethods

were found to agree closely with the macroprocedure in ranking the

soft winter varieties. One of these micromethods has been used by the

two Federal laboratories working with pastry wheats since 1950 (Bode,

1959; Barmore, 1958). Good quality pastry flours produce larger cookies

than poor quality flours.

I. COLOR

Historically, white bread has been a status symbol. The degree of

“whiteness” in flour is dependent on contamination by bran, shorts, and

carotenoid pigments. A high level of carotenoids imparts a yellow color to

flour which is considered objectionable in bread flour, but paradoxically

is highly prized in macaroni flour. Bleaching bread flour neutralizes the

color effect of this pigment. Coleman and Christie (1926) devised a

simple, rapid method of arriving at an objective color value for varieties

and selections. A colorimetric reading was made of a gasoline extraction

of the carotenoid pigments from 20 g. of ground and sifted wheat meal.

The pigment content of the finished durum wheat products is influenced by an enzyme, lipoxidase, which reduces the desired yellow

color in the dough during processing ( Irvine and Anderson, 1953). Irvine

and Anderson have devised an assay for this enzyme and shown that

pigment content of macaroni can be predicted from 20 g. of grain.



BREEDING WHEAT QUALITY



99



J. ALKALINEWATERRETENTION

CAPACITY

Flour swells in an alkaline as well as an acid environment. The alkaline water retention capacity ( AWRC test) (Yamazaki, 1953) and the

alkaline viscosity test (Finney and Yamazaki, 1953) have both been

developed as a result of this property. The AWRC test requires 15 g.

of flour plus 75ml. of 0.1 N sodium bicarbonate solution with agitation

followed by centrifugation and decantation. The gain in weight is expressed as a percentage. The results of the correlation of the 6-year

varietal means of cookie diameters and the results of this test gave a

coefficient of 0.95. The advantage that this test possesses over other

existing physicochemical methods is that the results may be compared

directly with cookie diameter without the necessity for protein or ash

adjustment.

The alkaline viscosity test requires 20 g. of flour and an instrument

for measuring viscosity, commonly the MacMichael viscosimeter. The

flour is treated with 60 ml. of water and two additions of 1 ml. each of

normal sodium bicarbonate followed by the determination of the viscosity. The values obtained by this test as well as by the lactic acid

viscosity test are highly influenced by protein content, and in order to

compare them with cookie diameters they are adjusted to 9 per cent

protein. Finney and Yamazaki ( 1953) obtained correlation coefficients

of -0.93 between cookie diameter and adjusted alkaline viscosities and

-0.81 for cookie diameters and adjusted acid viscosities.

V. Micromilling Methods



Flour milling would be a relatively simple process if the sole objective was pulverization of the entire wheat kernel to a meal. Efficient

and maximum separation of the starch fraction (endosperm) from the

bran (seed coat) and germ (embryo) is necessary in the production

of a white flour. Many milling problems arise from the economic necessity of obtaining maximum white flour extraction from a lot of wheat

in a minimum period of time. Development of micromills capable of

extracting flour from small samples of wheat is a necessary adjunct to

microquality tests if these tests are to be of value to the plant breeder.

The commercial flour mill represents a complex, interlocking array

of rollers, sifters, and air classifiers. The challenge in the development

of micromills has been a simulation of the physical aspects of a commercial mill in a miniaturized system with a minimum sacrifice in capabilities. The Allis Chalmers laboratory mill met this challenge and became a standard item of equipment in research and quality control



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III. Milling and Baking Research Laboratories

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