12 BULLETIlSr 788, U. S. DEPAKTMENT OF AGKICULTURE. 



The net change in weight due to change in moisture content from 

 the beginning of the tempering process to the end of the milUng 

 process was, for mill No. 1, a gain of 0.29 per cent; for mill No. 2, a 

 loss of 1.01 per cent; and for mill No. 3, a loss of 0.90 per cent. From 

 a comparison of all the results given in part 5, it may be concluded 

 that the amount of water added in tempering compensated for the 

 evaporation of moisture diu-ing miUing only in the case of mill No. 1. 



Whether or not the calculated gains and losses given here for each 

 of the three mills agree with the gains and losses ascertained from 

 an actual weighing of the wheat and the products milled therefrom 

 is not known except in the instance of mill No. 1. Calculations 

 made from the daily and weekly reports of this mill giving the scale 

 readings of the wheat before cleaning and tempering, after tempering, 

 and of the products from the packers showed approximately the 

 same results as those given in the table. 



In the actual milling of wheat on a commercial scale, the correct 

 percentage of gain or loss resulting from the addition or evaporation 

 of moisture during the tempering and miUing processes, whether 

 based on differences in moisture content or in weight, can not be 

 obtained exactly, for the reason that the moisture content is affected 

 by certain variable conditions, and calculations which would be 

 based upon any samples obtained would be incorrect to the extent 

 of their variation from the true average condition. Both the mois- 

 ture content of the untempered wheat, and the amount of water 

 added during tempering are also likely to vary from time to time, 

 resulting in a proportionate variation in the moisture content of the 

 tempered wheat. Furthermore, any change in the adjustment of 

 the roUs and other machines or in atmospheric conditions may 

 cause a shght variation in the evaporation of moisture and the 

 milling yield of the different products. AU such variations neces- 

 sarily affect the accuracy of the results. 



SUMMARY OF RESULTS. 



(1) The decrease in the moisture content of the various roU streams 

 from the head to the tail of the milling process was closely related to 

 the amount of water added to the wheat during tempering. 



(2) It appeared that very little of the moisture added to the 

 wheat during tempering penetrated farther than the pericarp or 

 outer coatings of the kernel. 



(3) The moisture content of the better grades of flour miUed, irre- 

 spective of the amount of water added during tempermg, closely 

 corresponded to the percentage of moistm-e contained in the un- 

 tempered wheat. 



(4) The amount of water added in tempering compensated for the 

 evaporation of moisture during milling only in the case of one of 

 three mills examined. 



WASHINGTON : GOVERNMENT PRINTING OFFICE : 1919 



