502 
Proteins, unlike starches, combine with acids 
and alkalis. Such combinations differ in their 
properties according to the quantity of acid or 
alkali which they contain. Similar differ- 
ences are also produced in the properties of 
proteins by the action of salts. Among the 
most important of the effects of acids, alkalis 
and salts upon proteins is the modification of 
the swelling in water, and partly as a result 
of this, of elasticity, tenacity and cohesive- 
ness. Another important effect is a change in 
the solubility of the proteins. 
As the amount of acid or alkali combined 
with gluten varies, the amount of water which 
ean be absorbed varies from 24 to 33 times 
the weight of the gluten itself.®,® 7 Certain 
salts also have an important effect upon the 
swelling of gluten.§ 
In spite of the fact that such phenomena 
are more or less similar to those which may 
be observed with other proteins, there are 
many properties of gluten which are very 
different from those of other known protein 
substances. The unique properties of gluten 
make possible the manufacture of good leay- 
ened bread. 
DOUGH 
The swollen, coherent gluten imparts to 
wheat-flour dough the properties of tenacity 
and elasticity that are peculiar to it. It per- 
mits the stretching and distending of the mass 
in bread-making. As a result the volume may 
increase four or five fold. Dough made from 
other grains, even though containing more pro- 
tein and possessing a greater capacity to ab- 
sorb water, is both less elastic and less co- 
herent. When stretched such doughs break. 
The baker calls them “ short.” 
5 Wood, T. B., ‘‘The Chemistry of Strength of 
Wheat Flour,’’ Jour. Agricultural Science, Vol. 2, 
Part 3, pp. 267-277, 1907. 
6 Wood, T. B., and Hardy, W. B., ‘‘ Electrolytes 
and Colloids: The Physical State of Gluten,’’ Pro- 
ceedings Roy. Soc. B, UXXI., pp. 31-43, 1909. 
7 Unpublished observations. 
8 Wood, T. B., ‘‘The Chemistry of Strength of 
Wheat Flour,’’ Jour. Agricultural Science, Vol. 2, 
Part 2, pp. 139-160, 1907. 
SCIENCE 
[N. S. Vou. XLVIII. No. 1247 
The extent to which dough can be distended 
yaries with the quantity and with the physical 
condition of the gluten. Within certain limits 
the baker can therefore improve the rising of 
dough by modifying the physical condition of 
gluten. Thus, for instance, increasing the 
acidity of dough will increase its elasticity® 
and certain salts, such as calcium sulphate, 
may have a similar effect. 
THE FERMENTATION OF SUGAR 
Bread is leavened by the formation of ecar- 
bon dioxide within the dough through the 
fermentation of sugar by yeast. Yeast can 
freely utilize either cane sugar or glucose for 
the production of carbon dioxide. In Amer- 
ican baking practise, where a short fermenta- 
tion is usually preferred, sugar is therefore 
added to dough. The proper amount of sugar 
depends upon the conditions of the fermenta- 
tion. It is, however, as the present practise 
of certain nations and the early history of 
baking prove, not necessary to add any sugar 
at all, for a small amount of sugar is present 
in flour,®,11 and more is slowly produced 
from starch during fermentation by the action 
of enzymes. But sugar can not be left out 
unless the whole practise of the baker differs 
from that now followed in America. 
THE PRODUCTION OF CARBON DIOXIDE BY YEAST 
Yeast is very sensitive to slight changes in 
the dough batch. For instance, activity at 
30° CO. (86° F.) is about twice as great as 20° 
C. (68° F). The production of carbon di- 
oxide is, however, much decreased by the large 
quantity of salt which is added to the dough 
with the water, sugar and shortening. By 
means of this effect of salt on the activity 
of yeast the baker commonly controls the 
9 Henderson, L. J., Fenn, W. O., Cohn, E. J., 
‘The Influence of Electrolytes upon the Viscosity 
of Dough’’ Journal of General Physiology. 
10 Wood, T. B., ‘‘The Chemistry of Strength of 
Wheat Flour,’’ Jour. Agricultural Science, Vol. 2, 
Part 2, pp. 267-277, 1907. 
11 Maurizio, Landwirtschaftliche 
XXXI., 1902. 
Jahrbiicher, 
