DIGESTIBILITY OF BREADS. 



63 



B — The influence of three baking powders on the digestion of known quantities of 

 certain simple substances, such as starch, fibrin and gluten. 



C — The influence of alum and of some salts formed during the decomposition of 

 baking powders on the digestion of starch, fibrin, etc. 



A. 

 The Relative Digestibility of Some Varieties of Bread. 



The following varieties of bread were used in these experiments : (1) Yeast bread 

 (2) Bread made with tartaric acid bakiug powder, (3) Bread made with a phosphate, 

 powder, (4) Bread made with two varieties of alum powder, (5) Unleavened bread, i.e., 

 plain flour and water. The yeast bread, or the unleavened bread, was taken as a standard, 

 all the experiments being strictlj^ comparative. In each series the same flour, used to pre- 

 pare the bread made with the bakiug powders, was employed to make the standard bread. 

 In each case, also, the directions given for the use of the powder were strictly followed and 

 the loaves were made as nearly as possible of the same size. 



Method. — In every experiment, unless otherwise noted, two grammes of the crumb 

 were taken. This quantity in a few cases includes the natural moisture of the bread, 

 but usually it was dried at 100' C, and reduced to powder before weighing to eliminate 

 the error of variation in moisture. 



The digestions were all carried on in a carefully regulated incubator at a constant 

 temperature of 40" C, and the relative digestibility of the breads was determined either 

 by weighing the dried undigested residues after an hour or two, or by determining the 

 quantity of dextrose formed by the amylolytic ferments under similar conditions. The 

 ferments used were obtained as follows : — A cold glycerine extract of pig's stomach yielded 

 the pepsin, the trypsin was prepared from fresh dog's pancreas by the method recom- 

 mended by Dr. Cranston Charles of St. Thomas Hospital, ' and the ptyalin was from fresh 

 mixed human saliva diluted to ten volumes and filtered. 



Series I. — Tlie Digest ibilily of Breads made with Almn Baking Poioder compared with that of 

 Yeast Bread made from the same Flour. Peptic Digestion. 



Taiîle 1. — PerTic Digestion. 



' Charles's Physiological and Pathological Chemistry, ed. 1885, p. 169. 



