UNITED STATES DEPARTMENT OF AGRICULTURE 
- BULLETIN No. 1013 
Contribution from the 
Bureau of Markets and Crop Estimates 
H. C. TAYLOR, Chief J&&*&3 ! U 
1 
Washington, D. C. PROFESSIONAL PAPER December 22, 1921 
THE INFLUENCE OF RELATIVE HUMIDITY AND MOIS- 
TURE CONTENT OF WHEAT ON MILLING YIELDS AND 
MOISTURE CONTENT OF FLOUR. 
By J. H. Shollenbeegek, Grain Supervisor, in Charge Milling Investigations. 
CONTENTS. 
Page. 
Introduction 1 
Humidity 2 
Normal moisture content 2 
Material and method of experiments 3 
Influence of relative humidity on total yield of mill products and invisible loss 4 
Comparison of the influence of relative humidity and of moisture content of wheat 
on milling yields 6 
Influence of relative humidity on moisture content of flour 7 
Comparison of the influence of relative humidity and of moisture content of wheat 
on the moisture content of flour 8 
Influence of atmospheric temperature on the total yield of mill products 10 
Summary 10 
INTRODUCTION. 
It is common knowledge among millers that the total weight of 
the products obtained in milling almost invariably differs from the 
weight of the wheat used. This difference in weight is due largely 
to changes occurring in the moisture content of the wheat during 
its preparation for grinding and throughout the process of milling ; 
therefore, any factor influencing the amount of moisture which be- 
comes added to wheat or evaporated therefrom in its preparation 
for milling and during the different steps of milling influences to 
that extent the percentage yield of mill products. 
The results of certain milling tests conducted in the experimental 
mill operated by the Federal Bureau of Markets and Crop Estimates 
at Washington, D. C, indicate the nature of some of these factors and 
the extent of their influence. Information was obtained on the fol- 
lowing subjects: The influence of the relative humidity of the air 
within the mill and of the moisture ' content of hard wheats when 
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