Ae ‘y OOPS 
PROTEIDS | 33 
sugar as possible is produced. At this point the plantlets 
are killed by heat so that they will not use up any of the 
sugar they have made. The sweet substance is then dis- 
solved out by soaking the malted grains in water. From the 
liquid so sweetened, lager beer and other malt liquors are 
made by subsequent fermentation with yeast. Diastase 
separated from malt may be used instead of an acid to con- 
vert starch into sugar. 
30. Proteids. Let us return now to that other constituent 
of the wheaten dough, the elastic material which remained 
after removal of the starch. This is known as gluten! and 
is a mixture of several substances which belong to the class 
known as proteids.2. To this class belong also the substances 
which form the chief part of our own flesh and blood—and 
indeed, mainly constitute the living substance of all plants 
and animals. Hence, proteids must be regarded as the 
most precious of all food substances. Like the carbohydrates 
they contain carbon, hydrogen, and oxygen (though in some- 
* what different proportions), but in addition they always 
have a certain amount of nitrogen, and usually a little sulphur 
and phosphorus. The nitrogenous nature of the proteids 
is made evident by the pungent ammoniacal odor which 
is given off when any of them are burned,—ammonia being 
_ NH;. Although in chemical composition proteids are all 
ae A re 
very much alike, there are important differences in their 
solubility—some, like white of egg, dissolving in cold water, 
while others, such as those of the “wheat gum” are in- 
soluble. Among the latter is a form of proteid called glutin 
or gliadin which gives to wheat-gluten its wonderful tenacity 
and elasticity. 
It is a significant fact that wheat is the only one of the 
cereals which contains gliadin in any considerable amount, 
although it should be said that rye contains a closely similar 
proteid. Macaroni, which owes its consistency chiefly to 
gliadin, is therefore made only from wheat; and wheaten 
dough alone possesses just the right tenacity and elasticity 
for making the lightest, spongiest loaf. The lightest rye bread 
1Glu’ten < L. glutus, tenacious. 
* Pro’te-id < Gr. protos, before. 
