UNITED STATES DEPARTMENT OF AGRICULTURE 
BULLETIN No. 557 
Joint Contribution from the Bureau of Plant Industry, WM. Ao *\& 
TAYLOR, Chief, and the Office of Markets and Rural 
4U9"^WU 
Organization, CHARLES J. BRAND, Chief 
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Washington, D. C. 
May 18, 1917 
A COMPARISON OF SEVERAL CLASSES OF AMERI- 
CAN WHEATS AND A CONSIDERATION OF SOME 
FACTORS INFLUENCING QUALITY. 1 
By L. M. Thomas, 
Grain Supervisor, in Charge of Milling and Baking Investigations. 
CONTENTS. 
Page. 
Introduction 1 
Factors of importance in determining the 
quality of wheat 2 
Milling yield and flour color 2 
Flours of high and of low strength 3 
Loaf volume and texture 3 
"Water absorption. 5 
Classes of wheat studied 5 
Milling yield and related factors 6 
Yield of flour 6 
Yield of bran and shorts 7 
Moisture content and flour yields 7 
Flour yield and weight per thousand kernels. . 9 
Flour yield and weight per bushel 10 
Page. 
Color of flour and bread 14 
Relation of yield and color to test weight and 
soundness 15 
Inseparable foreign material, flour 5ield, and 
color of bread 17 
Flour strength 18 
Comparisons of loaf volume 18 
Comparisons of texture 21 
Relation between crude protein in wheat and 
the strength of flour 22 
Protein content of wheat and flour 24 
Water absorption of flour 25 
Summary 25 
INTRODUCTION. 
The task of placing wheat classification and grading on a scientific 
basis involves a consideration of two important problems, the first of 
which is the investigation of the fitness of the several types of wmeat 
for the manufacture of white flour and the adaptation of the flour 
from these several types to the manufacture of different kinds of 
bread products. This primarily concerns the division of wheats of 
distinctly different character into general. classes. 
1 The investigations reported herein were made in the Office of Grain Standardization 
of the Bureau of Plant Industry, under the direction of Dr. J. W. T. Duvel, Crop Tech- 
nologist in Charge, in cooperation with the chemical department of the North Dakota 
Agricultural Experiment Station. Since August 18, 1916, the grain-standardization 
investigations of the Department of Agriculture have been administered jointly by the 
Bureau of Plant Industry and the Office of Markets and Rural Organization in connection 
with the enforcement of the United States Grain Standards Act, 
91418°— Bull. 557—17 1 
