CHAPTER XVII 

 VARIOUS FACTORY BY-PRODUCTS 



I. FLOUR AND CEREAL MILL FEEDS 



IN the manufacture of flour or cereal products (breakfast foods) 

 a large number of by-products are obtained that are of the highest 

 value for stock feeding. 



The flour-mill feeds are well-known by-products that have long 

 been standard feeding stuffs in all parts of the country where live- 

 stock are kept. These are bran, middlings or shorts, and low- 

 grade feeding flour. A brief statement of the minute structure of 

 the wheat kernel will make clear the characteristic differences in 

 these by-products. 



The wheat berry is covered by three different coatings of tough, 

 thick-walled cells, which contain a considerable proportion of fiber 

 and but little starch. Directly beneath the innermost seed-coat is 

 a layer of cells, very rich in protein, called the aleurone layer; 

 inside of this is the soft white portion (endosperm) of the berry, 

 made up of cells largely filled with starch grains. These also con- 

 tain protein substances, known under the name of gluten (gliadin 

 and glutenin, see p. 9). Within the inner starchy portion of the 

 berry is found the germ containing the embryo of the wheat plant, 

 The following figures show the approximate proportion of the differ- 

 ent parts of the wheat berry, according to Bessey : 



Coatings or bran layers ... 5 per cent 



Aleurone layer 3 to 4 per cent 



Starch cells 84 to 86 per cent 



Germ 6 per cent 



Wheat is the main bread grain in this country. In the manu- 

 facture of flour the wheat is first passed over a series of screens 

 which remove the impurities contained therein, such as weed seeds, 

 chaff, etc. (p. 170) . It is then scoured, and, after being heated some- 

 what, is run through a series of rollers, set at decreasing distances 

 apart, so that the kernels are gradually broken into smaller and 

 smaller pieces. The fine floury portion formed is separated after 

 each "break," and the tough outer seed-coats are thus gradually 

 freed from adhering flour and make up the bran. The aim of the 

 miller is to obtain all the starch cells and gluten possible from the 



179 



