COMPOSITION OP GRAIN AND FLOUK. 127 



a. All grains, as sold in market, or stored in gra- 

 naries, and in the state usually considered dry, contain 

 from 10 to 16 per cent of water, which may be driven 

 off by a gentle heat. Nearly every variety of flour has 

 a little larger amount than the above. 



We will now notice the composition of some of the 

 leading varieties of grain, in their organic part. 



Wheat is one of the most important of all crops. 

 The grain contains from 50 to 70 per cent of starch, 

 from 10 to 20 per cent of gluten, and from 3 to 5 per 

 cent of fatty matter. The proportion of gluten is said 

 to be largest in the grain of quite warm countries. 



a. It is a singular fact, that in all the seeds of 

 wheat, and of other grains, the principal part of the 

 oil lies near, or in the skin, as also does a large por- 

 tion of the gluten. The bran owes to this much of 

 its nutritive and fattening qualities. Thus, in refining 

 our flour to the utmost possible extent, we diminish 

 somewhat its value for food. The phosphates of the 

 ash also lie to a great degree in the skin. 



b. These substances seem all to be collected here 

 for the benefit of the young shoot. When it first 

 starts, and until it appears above the surface and ex- 

 pands its first true leaves, it has to depend for nutri- 

 ment on the stores already provided in the seed. 

 These have been prepared not only, but deposited in 

 that part of the seed most near to the germ, so that 

 its nourishment may be easily and readily obtained. 



The best fine flour contains about 70 Jbs. of starch 

 in each hundred. The residue of the hundred lbs. 

 consists of 10 or 12 lbs. gluten, 6 to 8 lbs. of sugar and 

 gum, 10 to 14 lbs. of water, and a little oil. 



Gluten, as has been mentioned, swells up to a great 

 bulk when heated, and becomes full of holes. The 

 same thing takes place in the baking of bread. It is 

 the gluten that gives tenacity to the dough, so that 

 when bubbles of gas are liberp^d during the fermen- 



