FREE INSTITUTE OF SCIENCE 



THE CHEMISTRY OF BREAD-MAKING 



79 



is baked. Gluten bread contains a maximum of nitrogenous matter and a 

 minimum of carbohydrates, and is used in the restricted dietary of diabetics. 

 Rye bread may be, as it commonly is, made from a mixture of rye and wheat 

 flours — the Tafelbrod or Knuppel of the Germans; or it may be made from 

 straight rye flour of various grades and by different processes, as in Pumper- 

 nickel, Schwarzbrod, and Kommisbrod. 



Rolls are small individual portions of any of the above varieties of bread. 

 The ordinary white bread made from bolted flour is the form that will be re- 

 ferred to mainly; other varieties will be mentioned, when necessary, in order 

 to illustrate some particular chemical change. 



The first set of factors to be considered are the proximate chemical con- 

 stituents of flour in comparison with leavened bread. The typical composi- 

 tion is as follows (figures in parts per hundred) : 



Water 



Protein 



Fat 



Carbohydrates 

 Ash 



It will be noticed that the water, fat, and ash are all higher in bread than 

 in flour. This is because water, shortening (fat) , and salt are added in making 

 the dough. The separate consideration of each of these constituents is now in 

 order. 



Water is mechanically present in all food-stuffs, from which it may be re- 

 moved by processes of dehydration or desiccation without materially altering 

 the composition of the food, though, of course, the physical properties and 

 usually the palatability are much changed. According to some authorities, 

 the water in stale bread is in a somewhat combined form as contrasted with the 

 water in fresh bread. The difference is shown by the fact that the propor- 

 tionate amount of water-soluble constituents is less in stale than in fresh bread 

 from the same loaf, which can be accounted for only on the theory that the 

 water has entered into some kind of a combination to form less soluble sub- 

 stances of different physical properties. The difference in the moisture con- 

 tent between fresh and stale bread is trifling, while the difference in physical 



