6 BULLETIN 557, U. S. DEPARTMENT OF AGRICULTURE. 
MILLING YIELD AND RELATED FACTORS. 
YIELD OF FLOUR. 
As has been said, flour yield is the most important consideration 
in determining wheat values. Figure 3 affords a comparison of the 
average flour yields of soft red winter, hard red winter, hard red 
spring, and durum wheats, and also the extreme and ordinary 
ranges for each class. While an extreme range in flour yield of about 
20 per cent was secured with the durum wheat and a somewhat nar- 
rower range for other classes, the ordinary ranges show a variation 
of only about 10 per cent. Over 90 per cent of the samples of soft 
red winter and hard red spring and 80 per cent of the durum samples 
yielded between 65 and 75 per cent of straight flour. The hard red 
winter samples ranged somewhat higher, as over 90 per cent yielded 
between 67 and 77 per cent of straight flour. 
In average flour yield the hard red winter wheat is about 2 per 
cent higher than the other classes, between which only small dif- 
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Fig. 3. — Diagram presenting a comparison of the yield of straight flour of four com- 
mercial classes of American wheat, showing their general range and the average 
for each class. The samples used represented the crop years from 1908 to 1913, 
inclusive, except those of soft red winter wheat, of which only samples of the 
crops of 1911, 1912, and 1913 are included. 
ferences are noted, although soft red winter wheat falls slightly be- 
low the hard red spring and durum wheats. That this poor showing 
of the soft red winter wheat is due in part to experimental error is 
very probable, as this wheat is very difficult to handle in an experi- 
mental mill, the flour being soft and fluffy, clinging to the spouts 
to an unusual degree and causing not only a greater average me- 
chanical loss but also greater moisture losses through evaporation. 
This is borne out by the figures in Table I, which shows that the 
average loss was 1.2 per cent greater for soft red winter wheat 
than for spring wheat. With durum wheat the opposite was true. 
Durum wheat reduced to a very coarse granular flour which showed 
practically no tendency to hang to the spouts and dust out. 
