Many conditions affect somewhat the composition of grains. Wheats illustrate this. The variety of wheat, soil, climate, all affect the composition of the resulting grain. The constituents that vary significantly are starch and protein. Wheat is planted in the fall or spring. It is called winter or spring wheat according to the time of planting. Winter wheats are usually softer than spring. Soft wheat contains less gluten (this is a protein) and somewhat more starch than hard. (See p. 20).

Different wheats are used differently. It is a very hard variety of wheat which is used in the manufacture of macaroni. There are white and red wheats as well as hard and soft. The grinding of wheat-grains makes further differences in the grades of flours. These serve different purposes according to their constitution as well as composition.

Constituents of the grain are not so arranged in it as to be found uniformly distributed throughout it. See diagram below. (Starch is usually in largest quantity near the center and protein near the hull. Wheat-hulls themselves make the bran used by cattle for food. The proportion of mineral salts and protein in it are higher than in the flours used as human food.

In bran: P 15%; salts, 8%.

In flour: P 8%-14%; salts, 1%-2%. - Olsen Milling flour follows harvesting and winnowing. "Screening" removes everything not grain. "Scouring" cleans the grain. "Breaking" with heavy rollers grinds it. "Bolting" sifts it. There are 5 breaks and many siftings through bolting cloth of increasing fineness.

Wheat-grain (With covering).

Products Of Milling

"Scalpings," coarsest; "dustings," finest; all others are called "middlings".

Siftings are mixed according to fineness.

Bran is last scalping and is cellulose mainly but with much protein and salts fixed in it.

WJieat-grain (No covering).