FREE INSTITUTE OF SCIENCE g^ 



THE CHEMISTRY OF BREAD-MAKING 



It is the tenacity of the gluten in the dough that holds the bubbles of gas intro- 

 duced by the leavening process and gives "lightness" to the bread. Flours 

 from wheats of different quahty or varieties differ markedly in their dough- 

 making quahties, and while all the causal factors are not yet known, it is be- 

 Keved that the elasticity of the gluten is largely dependent upon the presence 

 and amount of certain inorganic salts, especially phosphates. 



Gluten undergoes Httle or no chemical change in 'bread-making. Its 

 peculiar physical properties give to it its particular value. The soluble pro- 

 teins play a somewhat obscure and yet not unimportant part. It is believed 

 that they have the property of modifying the gluten to a certain extent, under 

 favorable conditions, and also that they change soluble starch into sugar. In 

 this respect they, or some one of them probably, show enzymic properties. 

 It is well known that if the proportion of soluble proteins exceeds a certain 

 ratio, the flour does not make good bread. 



Fat is a generic term applied principally to the glyceryl esters of fat-acids, 

 but also to alcoholic substances, as cholesterol. The fat of flour is very small 

 in amount (insufficient, indeed, to make good bread, so that it needs must be 

 reinforced by the addition of lard, butter, or other shortening agent to the 

 dough), and plays a very unimportant part in the chemistry of bread. It 

 consists of the glyceryl esters of oleic, palmitic, and stearic acids, and a very 

 small amount of lecithin (a phosphorus-containing fat) and of cholesterol. 

 The fats, which are such important food constituents, as a rule are almost 

 lacking in flour and bread, but their place is filled by the carbohydrates, which 

 are similar in effect, though of much less proportionate nutritive value. This 

 deficiency is also made up by the butter usually spread on bread when it is 

 eaten. 



Carbohydrate is a generic term describing an important group of organic 

 food substances in which the essential condition of composition is the presence 

 of carbon, hydrogen, and oxygen, the hydrogen and oxygen being in the rela- 

 tive proportion of two atoms of the former to one of the latter, i. e., the same 

 proportion as found in water, whence the common name, carbohydrate. 

 Carbohydrates may be divided into two classes — the insoluble, represented in 

 flour by starch and cellulose, which have the same empirical formula but differ 

 markedly in their physical properties, and the soluble, represented in flour by 

 the sugars, maltose and dextrose, and by dextrin, which has also the same 



