784 DISCUSSION ON WHEAT: 
Osborne, T. B., and C. G. Voorhees.—‘ The Proteins of the Wheat Kernel’ 
(‘ Amer. Chem. J.,’ 1893, 15, 392-471; 1894, 16, 524-535). 
Osborne, T. B., and I. F. Harris.—‘The Chemistry of the Protein Bodies of 
the Wheat Kernel’ (‘Amer. J. Physiol.,’ 1905, 13, 35-44; 1906, 17, 223-230, 
231-265). 
Sie C. E., and F. T. Shutt.—‘ Milling and Chemical Values of Grades 
of Wheat in Manitoba.’ (‘Bulletin Canadian Hxperimental Farm,’ No. 50, 1904; 
No. 60, 1907). 
Saunders, C. E., and F. T, Shutt.—‘ Quality in Wheat’ (Bulletin, No. 57, 
1907). 
Shite, F. T.—‘ The Relation of Composition of Flour to Bread Value’ (‘ Int. 
Congress of Applied Chemistry,’ London, 1909). 
Shutt, F. T_—‘ The Influence of Environment on the Composition of Wheat 
(‘J. Soc. Chem, Ind.,’ 1909, 28, 336-338). 
Snyder.—(‘ Minnesota Expt. Station Bulletin,’ 1904). 
Whymper, R.—‘ Microscopic Study of Changes occurring in Starch Granules 
during Germination of Wheat’ (‘ Int, Congress of Applied Chemistry,’ London, 
1909). 
Wood, T. B.—‘ The Chemistry of Strength of Wheat Flour’ (‘J. Agric. Sci.,’ 
1907, 2, 139-161; 267-277). 
Wood, T. B., and Hardy, W. B.—‘ Electrolytes and Colloids; the Physical 
State of Gluten ’ (‘ Proc. Roy. Soc.’ 1909, 13881, 38-43). 
9. An Analysis of the Factors contribuling to Strength in Wheaten 
Flour. By W. B. Harpy, F.B.S. 
Reduced to the simplest terms the physical properties of dough depend 
upon the protein complex gluten, starch grains and water. The greater 
the water-absorbing power of the glaten, that is the greater its water 
content, the less will be its tenacity and, within limit, the greater its 
ductility. 
Colloid bodies such as moist gluten have a sponge structure, and when 
solid particles are present the bars of the sponge-work may be seen under 
the microscope to spring from them. Thus solid particles may enter intimately 
into the framework, and by their size and number modify the thickness 
and length of the bars and the size of the interspaces. Rubber loaded 
with solid particles has elastic properties widely different from those of 
rubber free from particles, and moist gluten loaded with starch grains differs 
from gluten washed approximately free from them. It is less like elastic, 
more like putty, in its mechanical properties—the solid grains of starch 
act as though they enormously increased the internal friction. 
There has, so far as I know, been no exact work upon the influence of 
the size and number of the starch grains upon the mechanical properties 
of dough; in the absence of such information it is idle to pursue the point 
further. This may however be said; judging by what is known of the 
influence of embedded small particles in other cases the power of the 
dough to retain its shape may be due in some cases primarily to the nature 
and number of the starch grains. Whatever the influence of the starch 
grains may be, they operate as passive agents; the active mechanical pro- 
perties of dough, its tenacity and ductility, are due to the protein complex 
gluten. This is the labile elastic cement of the structure. 
Now gluten, even though it be prepared from the best Fife flour, has of 
itself neither ductility nor tenacity. In presence of ordinary distilled water 
it partly dissolves, the residue—the larger portion—forming a semi-fluid 
sediment destitute of tenacity. Why? Because tenacity and ductility are 
properties impressed on gluten by something else—namely by salts, by 
electrolytes, that is, which may be organic and may therefore he 
unrepresented in an ash analysis. 
