UNITED STATES DEPARTMENT OF AGRICULTURE 



„ BULLETIN No. 1013 



Contribution from the 

 Bureau of Markets and Crop Estimates 



H. C. TAYLOR, Chief S^fr*<$*SU 



•* 



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. Shollenbergee, 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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