USE OF WHEAT 1 19 



178. The By-products of Wheat consist of the outer coats, 

 the aleurone layer, the embr}^o, and such portions of the endo- 

 sperm as cannot, by the common process of milling, be removed 

 from the aleurone layer. There are a number of grades of 

 these by-products, depending principally upon the relative pro- 

 portion of outer coats to endosperm. The common grades are 

 bran, shorts and middlings, while a low grade of flour kno\\Ti as 

 "red dog" or "dark feeding flour" is sometimes sold for feeding 

 purposes. Bran and shorts are essentially the same, except 

 that in the process of milling the outer coats in the latter are 

 more thoroughly pulverized; while the middlings contain a 

 larger portion of the endosperm, and are therefore more starchy 

 and dense than bran or even shorts. In the bran the outer 

 coats are in large flakes, wdth portions of the aleurone layer 

 and endosperm attached, thus making a light, bulky product. 

 While the embr}'o itself constitutes a much smaller proportion, in 

 the process of milling about eight per cent of the grain is 

 removed as embr}^o. (64) Care is taken to remove these em- 

 bryos, because their introduction into the flour injures its keeping 

 qualities, and its nitrogenous compounds are not suitable for 

 breadmaking purposes.^ On account of their high nitrogen, 

 phosphorus and fat content, they are a valuable addition to the 

 by-products. They are sometimes found in the bran and some- 

 times in the middlings. As in the process of milling they are 

 separated from the rest of the products, it is optional with the 

 miller where they are put. The yellowish flattened embryos are 

 readily recognized in the mill products. 



179. Composition of By-products. — The analyses that have 

 been compiled show very great variations in every constituent 

 in different samples of bran, shorts and middlings.^ Taking 

 them as a class, the ash has been found to vary from 1.4 to 7.8 

 per cent; the protein from 10. i to 20.0 per cent; the crude 



I The Chemistr)' of Plant and Animal Life, p. 307. 

 » U. S. Dept. of Agr., Office of Expt. Sta. Bui. 11. 



