The wheat plant belongs to the grass family. The part that is used for food is the fruit or seed. This consists of three parts:

(1) The germ, or embryo, which is the part of the seed that reproduces. It is composed of cellulose, protein, sugar, and a large proportion of fat.

(2) The kernel, or endosperm, which is the central part of the grain. It consists of a cellular structure, which holds the starch granules, some protein, and sugar.

(3) The bran or outer covering, which is composed largely of cellulose and mineral matter, and contains a pigment or coloring matter. The bran forms a protective covering for the wheat grain and is made up of six layers. The five outer layers contain little but cellulose and mineral matter, but the innermost layer consists of rectangular cells filled with a protein called cerealin, or aleurone, and is the part of the grain which is richest in protein.

In the early methods of milling, this layer was removed with the bran, but the modern methods make it possible to separate the outer bran layer, retaining the aleurone layer, thus making what is known as entire wheat flour.

Graham flour is made by grinding all of the wheat with the exception of the embryo. It thus contains the bran. It is useful when coarse food is needed to stimulate the action of the large intestine to prevent constipation. The bran itself may be made into cookies, etc., and eaten for this purpose.

Protein In Wheat

Wheat is the most important grain used for bread making on account of the physical properties of two of its proteins, called gliadin and glutenin. When mixed with water, these substances unite to form gluten. Gluten has the power of absorbing nearly three times its weight of water and forming a tough, sticky, elastic mass. When carbon dioxide is produced in dough, it seeks to escape, but is retained by the expansion of the elastic gluten, thus causing the dough to rise.

Wheat is known as spring wheat and winter wheat. The spring wheat is planted in the spring and ripens or matures in the late summer. It is grown mainly in the northwestern parts of the United States and in the Canadian Northwest. The flour made from spring wheat is the best for bread making and for all forms of yeast mixtures.

Winter wheat is planted in the fall and it ripens in the early summer. It is grown in the sections of the country where the winters are less severe than in the Northwest, - in Ohio, Michigan, Indiana, etc., and in more southern lati-tudes. It is a softer wheat than spring wheat and makes a whiter flour, which is used for cakes, pastry, etc.

Note

(a) Plant wheat in wet cotton, keeping it moist until the wheat plant grows. Note changes from time to time in the appearance of the wheat. Student write description of the sprout-ing of the wheat grain, using any standard botany for reference.

(b) Examine a section of wheat under the microscope, noting bran coats, aleurone layer, endosperm, and embryo. Stain a sec-tion of the wheat with iodine, which will turn the starch purple and the protein yellow. Make drawing of a section of wheat. Why has nature stored so many food principles in this little grain of wheat ?

(c) Examine winter wheat and spring wheat flour, whole wheat flour, graham flour. Sift and examine the residue, if any, in the sieve. Compare color, texture, cohesion (press in hand).

To determine the composition of wheat flour.

Experiment 64

Make a small amount of flour into a stiff dough. Put into a piece of fine cheesecloth and knead in a bowl of cold water until only a sticky mass is left in the cloth. Collect this. Note its physical properties. Work with the fingers for some minutes. Does the gluten become more elastic with knead-ing? Give one reason for kneading bread dough. Form part of the gluten into a ball and bake. What is the effect of heat upon it?

Experiment 65

Test some of the gluten from the above ex-periment to see if it is protein ? starch ? sugar? See identification test for protein, page 69; for starch, page 21; for sugar, page 44.

Experiment 66

Boil some of the water in which the flour from experiment 64 was washed. Cool and test for starch.

Experiment 67

Let starch settle to bottom of the bowl in cup. Remove some of the clear top liquid and test for sugar.

Experiment 68

(To be performed by the teacher.) Mix a little dry flour with ether, chloroform, or benzine. Filter, letting the filtrate drop on clean glass. Let the liquid evaporate. What is left on the glass ?

Caution

The fumes of chloroform, ether, and benzine are very inflammable. Do not use with fire or light burning in the room.

Experiment 69

Burn a little flour in a porcelain crucible for several hours, or until only a white ash is left. What part of the flour is this ?