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 whité portion (endosperm) of the berry, 
made up of cells largely filled with starch grains. These also con- 
tain protein substanc2s, 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, os ysaeeniewess cates 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). Itis 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 
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