layers; _c_, aleurone cells; _d_,
germ. (After KOeNIG.)]

153. Composition of Wheat and Flour.--In addition to 12 to 14 per cent
proteids, wheat contains 72 to 76 per cent of starch and small amounts
of other carbohydrates, as sucrose, dextrose, and invert sugar. The ash
or mineral matter ranges from 1.7 to 2.3 per cent. There is also about 2
per cent fiber, 2.25 per cent ether extract or crude fat, and about 0.2
per cent organic acids.

Summary:

COMPOSITION OF WHEAT FLOUR

========================================================
| Per Cent
Water | 12.00
|
{Potash } |
{Soda } |
{Lime } |
Ash {Magnesia } | 2.25
{Phosphoric anhydrid} |
{Sulphuric anhydrid } |
{Other substances } |
|
{Albumin 0.4} |
{Globulin 0.9} |
Protein {Gliadin 6.0} | 13.00
{Glutenin 5.3} |
{Other proteids 0.4} |
Other nitrogenous bodies, as amids, lecethin | 0.25
Crude fat, ether extract | 2.25
Cellulose | 2.25
Starch | 66.00
Sucrose, dextrose, soluble carbohydrates, etc.| 2.00
=======================================================

154. Roller Process of Flour Milling.--Flours vary in composition,
food value, and bread-making qualities with the character of the wheat
and the process of milling employed. Prior to 1870 practically all
wheat flour was prepared by grinding the wheat between millstones; but
with the introduction of the roller process, steel rolls were
substituted for millstones.[60] By the former process a smaller amount
of flour was secured from the wheat, but with the present improved
systems about 75 per cent of the weight of the grain is recovered as
merchantable flour and 25 per cent as wheat offals, bran, and
shorts[61].

[Illustration: FIG. 38.--GRANULAR WHEAT FLOUR PARTICLES.]

The wheat is first screened and cleaned, then passed on t