given, however, of the term
"patent flour," as usage varies the meaning in different parts of the
country.

155. Grades of Flour.--Flour is the purified, refined, and bolted
product obtained by reduction and granulation of wheat during and after
the removal of the branny portions of the wheat kernel. It is defined by
proclamation of the Secretary of Agriculture, under authority of an
act of Congress, as: "Flour is the fine, sound product made by bolting
wheat meal, and contains not more than thirteen and one half (13.5) per
cent of moisture, not less than one and twenty-five hundredths (1.25)
per cent of nitrogen, not more than one (1) per cent of ash, and not
more than fifty hundredths (0.50) per cent of fiber."

[Illustration: FIG. 40.--GRINDING FLOOR OF FLOUR MILL,
RUSSELL-MILLER MILLING CO., MINNEAPOLIS, MINN.]

Generally speaking, flour may be divided into two classes, high grade
and low grade. To the first class belong the first and second patents
and, according to some authorities, a portion of the straight grade, or
standard patent flour, and to the second class belong the second clear
and "red dog." About 72 per cent of the cleaned wheat as milled is
recovered in the higher grades of flour, and about 2 or 3 per cent as
low grades, a large portion of which is sold as animal food. The high
grades are characterized by a lighter color, more elastic gluten, better
granulation, and a smaller number of debris particles. Although the
lower grade flours contain a somewhat higher percentage of protein, they
are not as valuable for bread-making purposes because the gluten is not
as elastic, and consequently they do not make as good bread. If the
impurities from the low grades could be further eliminated, it is
believed that less difference would exist between high and low grade
flours.

Various trade names are used to designate flours, as a 95 per cent
patent, meaning that 95 per cent of the total flour is included in the
patent; or an 85 per cent patent, when 85 per cent of all the flour is
included in that particular patent. If all the flour streams were
purified and blended, and only one grade of flour made, it would be
called a 100 per cent patent. An 85 per cent patent is a higher grade
flour than a 95 per cent patent.

[Illustration: FIG. 41.--SILK BOLTING CLOTH USED IN
MANUFACTURE OF FLOUR, MAGNIFIED.]

156. Composition of Flour.--The composition of the different grades of
flour made from the same wheat is