12 BULLETIN 788, U. S. DEPARTMENT OF AGRICULTURE. 
The net change in weight due to change in moisture content from. 
the beginning of the tempering process to the end of the milling 
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 during milling 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 milling 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 rolls and other machines or in atmospheric conditions may 
cause a slight variation in the evaporation of moisture and the 
milling yield of the different products. All such variations neces- 
sarily affect the accuracy of the results. 
SUMMARY OF RESULTS. 
(1) The decrease in the moisture content of the various roll 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 milled, irre- 
spective of the amount of water added during tempering, closely 
corresponded to the percentage of moisture 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 
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