9 



piled loaves. They found that as a rule the wheats with the largest 

 nitrogen content gave the strongest flours, but this rule was by no 

 means absolute. They showed that where wheats were grown under 

 similar conditions the nitrogen contents was a fairly satisfactory 

 index of strength ; when, however, conditions as to soil or climate 

 varied, this did not hold. The results obtained by various manurial 

 treatments were not consistent, and at Woburn* the effect of manures 

 on strength as determined by baking trials was so small as to be 

 negligible. 



Professor Woodf has examined this question of " strength " from 

 the chemical side and has devised methods of grading flours under 

 two heads according (1) to the size of loaf which the flour will pro- 

 duce, and (2) the factors which go to determine the shape of the loaf. 

 The first of those methods as employed by Wood consists of making 

 dough from the flour in the same manner as the baker and noting the 

 amount of gas given off as fermentation proceeds, the evolution of 

 the gas as well as its total volume should be noted. This gas (carbonic 

 acid) is produced by the fermentation of the sugars present in the 

 flour and is the cause of the dough rising. As fermentation proceeds 

 sugars are also produced by diastatic action from the other carbo- 

 hydrates of the flour. In the ordinary process of making bread the 

 flour is mixed with warm water and yeast until a uniform dough is 

 obtained; this is allowed to rest for some hours, when fermentation 

 sets in and the dough rises. It is then made into loaves, and these are 

 again allowed to remain for some time before being put into the oven. 

 During this time further evolution of gas takes place and it is quite 

 likely that this " second rise," as it has been termed by Hays and 

 Boss, J is a very important factor in determining the size of the loaf. 

 The loaves are then placed in the oven, where their shape and 

 size are soon fixed by the formation of the crust. Fermentation, 

 if it has not already ceased, is soon stopped owing to the death of 

 the yeast. 



The experiments which I have made with Egyptian wheats have 

 been confined to the first of these methods, viz. the size of the loaf 



* 'Journal K.A.S.E." Various Aumial Reports on Experiments on Whait. 

 ) " Journal of Agricultural Science," Vol. II. 

 j Minnesota Agric. Ex. St. Bulletin 62. 



