AMERICAN WHEAT AND CORN. 31 



Owing to the fact that the wheats were this year nearly all from the 

 Middle States and the West, they average more nearly the composition 

 shown previously for the Western country. 



Colorado has fallen off somewhat, owing to its poor crop, but the high 

 percentage of albuminoids in the Ohio samples has counteracted this 

 result, and the general average for the whole country, derived from the 

 407 samples analyzed, is somewhat higher than last year. 



The general conclusions of the previous bulletin are, however, not 

 essentially altered. 



CHEMISTRY OF THE ROLLER MILLING PROCESS OF GRADUAL REDUC- 

 TION. 



It is the object of milling to reduce the floury portion of the wheat- 

 grain to the finest possible form without injuring its physical condition, 

 and at the same time with complete exclusion of portions of the bran 

 and germ, and such refuse products as would injure its baking qualities 

 and color. An examination of the structure of the grain will enable us 

 to understand the difficulties to be met and the way in which the dif- 

 ferent products which have been analyzed are obtained. 



If a blade of wheat were much thickened and the two halves then 

 folded back upon themselves a transverse section of it would represent 

 a similar section of the grain, that is to say the two lobes would meet, 

 forming what is known in the grain as the crease within which would 

 be inclosed and hidden a portion of the outer covering. This explains 

 how difficult it is in preparing the wheat for milling to remove all the 

 foreign matter which this crease contains. On the exterior of the grain 

 there is found toward one end a collection of hair, and at the other end 

 appears the embryo or germ. A longitudinal section shows both of these 

 undesirable additions to the floury matter of the grain. Aside from its 

 exterior appearance the wheat-grain is essentially an embryo, the germ, 

 together with a supply of food, the endosperm or floury matter, sur- 

 rounded by several membranes or coats of greater or less importance. 

 On the exterior is the first membrane or cuticle, a very thin coating, 

 easily removed by rubbing. Next follows a more important, because 

 thicker, portion of the outer covering, consisting of two layers of cellular 

 tissue, the epicarp and endocarp. These three membranes together form 

 the outer covering of the grain, and from one of them, the epicarp, spring 

 the hairs which are found on one end. These envelopes are colorless 

 and very light, constituting only from 3 to 3 per cent, of the whole, 

 and are more or less easily removed by friction. From an examination 

 of a section of the grain it is seen that within the crease this is of course 

 impossible, so that while the preparation of the wheat for milling may 

 remove the hairs and much of the cuticle and dirt it cannot completely 

 free it from them. It is this inherent difficulty that the roller mills at- 

 tempt to overcome by splitting the grain along the crease and after- 

 wards cleaning it with brushes. 



