g TRANSACTIONS OF WAGNER 



THE CHEMISTRY OF BREAD-MAKING 



The classification into leavened and unleavened breads affords a sharp 

 distinction. The latter type is exemplified by the Matzoth, or Passover cakes, 

 consisting of flour and water made into thin cakes and baked, and also the 

 various types of crackers or biscuits, as they are usually called by the English, 

 which generally have salt and shortening (fat) present. The chemical changes 

 in unleavened bread and crackers are almost negligible. Beyond a limited 

 alteration of the starch to dextrin in some cases no chemical change takes 

 place, but the starch granules swell. 



The leavened bread, which is distinguished by its cellular or vesiculated 

 structure, is capable of subdivision into three groups, so far as preliminary 

 methods of preparation of the dough are concerned, and into many varieties, 

 depending upon composition and methods of baking. The three essentially 

 different methods of preparation are: i. Leavening the dough by aeration by 

 mechanical means; 2, leavening the dough by the employment of chemicals 

 which react to evolve a gas; 3, leavening the dough by the action of yeast 

 or bacteria. These three classes must be studied separately, so far as many 

 of the chemical changes involved are concerned, and will form the basis of the 

 present essay. The varieties into which bread may be divided are more easily 

 specified than precisely distinguished. Wheat bread may be white bread, 

 which is made from white bolted flour; Graham bread, so named from its 

 originator, who made it from a mixture of whole wheat flour and white flour; 

 or whole wheat bread, which is made from a straight unbolted flour containing 

 all the bran. White bread may be of the French or Vienna 1)^)6, which, being 

 baked in an oven containing steam, has an additional alteration of the surface 

 starch to produce the characteristic amber glaze on the outer surface. This is 

 often imitated by applying a wash of beaten whole eggs just before the bread 

 is placed in the ordinary oven. 



Graham bread is sometimes called brown bread, but the latter term ordi- 

 narily applies to a cake-Hke product, largely eaten in New England, made from 

 wheat flour and corn meal, with molasses and shortening. Milk bread is bread 

 in which milk has been used to replace all or part of the water employed in 

 mixing the dough. Germ bread is made from bolted flour mixed with germ 

 meal or flour, containing the fatty embryo of the wheat grain, which is usually 

 removed during the milling process to make the flour keep better. Malted 

 bread is a variety made with the addition of malt extract, the diastatic power of 

 which converts a considerable portion of the starch into sugar before the bread 



