2 BULLETIN 788, IT. S. DEPAETMENT OF AGRICULTURE. 



(flour, feed, and other mill products), the method used was that of 

 drying to constant weight a small portion of the sample in a water- 

 bath oven, at the temperature of boiling water. 



MOISTURE REQUIREMENTS OF WHEAT FOR MILLING PURPOSES. 



At the beginning of the process of milling, the miller gives much 

 consideration to the question of the moisture content of his raw ma- 

 terial. He knows that in order to secure the highest yields of flour 

 and to insure its greatest purity, the pericarp or outer cpatings of the 

 wheat kernel at the time of grinding must be of a certain toughness, 

 and the endosperm, or inner part, of a certain mellowness. The de- 

 gree to which these properties are possessed by the different parts 

 of the kernel is influenced largely by the amount of moisture present. 



Wheat when received at the mill is seldom, if ever, in the best 

 condition for milling, its moisture content being too high, too low, 

 or not properly distributed throughout the kernel. To acquire the 

 right moisture content for the outer and inner parts of the kernel, 

 thereby insuring the best possible milling condition for different 

 wheats, requires the application of various methods of tempering. 

 These methods may consist of a single, or successive, or of com- 

 bined applications of water, heat, or steam, working through a period 

 of time, ranging from a few minutes to as much as 36 hours, in order 

 that the moisture may be properly distributed within the kernel. 



Dry chmates and dry seasons naturally produce wheat of low 

 moisture content, and damp climates and wet seasons produce wheat 

 of high moisture content. There is, moreover, often considerable 

 range in the moisture content of wheat during any given season and 

 in any one locahty. Moisture determinations of samples obtained 

 from more than 5,000 cars of wheat, which were made by this depart- 

 ment at Kansas City, Mo., during the years 1910 to 1914, inclusive, 

 showed a range in the content of that factor from 7.4 per cent to 22 

 per cent. The fact that the moisture content of wheat may vary so 

 greatly is evidence that the problem of properly tempering wheat is 

 a complicated one. 



AMOUNT OF MOISTURE ADDED TO WHEAT DURING TEMPERING. 



In Table I is shown the percentage of moisture contained in wheat 

 before and after cleaning and tempering as found from moisture 

 determinations made on a series of samples secured from five dif- 

 ferent mills. The wheat of each mill was of similar class (hard red 

 winter) and grade, and contained, at the beginning of the tempering 

 process, approximately the same percentage of moisture. Different 

 amounts of water, however, were added by each mill. The difference 

 in moisture content of tempered and untempered wheat as shown in 

 this table indicates the change in that factor which resulted from 



