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Semi-Centennial Volume. 113 



bottle is then placed in a water bath, which is kept at 35° C. The bottle 

 is connected to an appai-atus for measuring gas, and the volume of gas 

 given off every hour is recorded. As already mentioned, all flours give 

 off about the same volume of gas during the first three hours. After 

 this length of time the volume of gas given off per hour varies greatly 

 with different flours. Thus a flour which will bake a large loaf gives 

 off under the conditions above described about 20 cc. of gas during the 

 sixth hour of fermentation, whilst a flour which bakes a small, light 

 loaf, gives off during the sixth hour of fermentation only about 5 cc. 

 gas. Having devised a feasible method of estimating how large a loaf 

 of any given flour will make, the problem of the shape and texture still 

 remains. Previous investigators had exhausted almost every chemical 

 property of gluten in their search for a method of estimating strength. 

 The author therefore determined to study its physical pi-operties. Now 

 gluten is what is known as a colloid substance. Such substances can 

 scarcely be said to possess definite physical properties of their own, for 

 their properties vary so largely with their surroundings. Their prop- 

 erties are profoundly modified by the presence of chemical substances. 

 Wheat, like most all plant substances, is slightly acid, and the degree of 

 acidity varies in different samples. Accordingly the effect of acids on 

 the physical properties of gluten was investigated and it was found 

 that by placing bits of gluten in pure water and in acid of varying con- 

 centration it could be made to assume any consistency from a state of 

 division so fine that the sepai'ate particles could not be seen except by 

 noticing their presence made the water milky, to a tough coherent mass 

 almost like India rubber. It was found, however, that the concentra- 

 tion of acid in the wheat grain was never great enough to make the 

 gluten really coherent. 



CHEMICAL ANALYSES. 



But wheat contains also varying proportions of such salts as chlorides, 

 sulphates and phosphates, which are soluble in water, and the action 

 of such salts on gluten was next tried. It was at once found that these 

 salts, in the same concentration as they exist in the wheat grain, were 

 capable of making gluten coherent, but that the kind of coherence pro- 

 duced was peculiar to each salt. Phosphates produce a tough and elastic 

 gluten such as is found in the strongest wheats. Chlorides and sulphates, 

 on the other hand, make gluten hard and brittle, like the gluten of very 

 weak wheat. 



The next step was to make chemical analyses to find out the amount 

 of soluble salts in different wheats. Strong wheats of the Fife class 

 were found to contain not less than one part of soluble phosphate in 

 1,000 parts of wheat, while Rivet wheat, the weakest wheat that comes 

 on the market, contained only half that amount. Rivet, however was 

 found to be comparatively rich in soluble chlorides, and in very small 

 amounts in strong wheats of the Fife class. After making a great many 

 analyses it was found that the amount of soluble phosphate in wheat 

 was a very good index of the shape and texture of the loaf which it 

 would make. The toughness and elasticity of the gluten no doubt depend 

 on the concentration of the soluble phosphate in the wheat grain, the 



8 — Acad. Sci.— 2199 



