Fig. 36.—Starchy (light-colored) and Glutinous (dark-colored) Wheats.
Fig. 37.—Longitudinal
Section of Wheat Kernel:
a, pericarp;
b, bran layers; c, aleurone cells;
d, germ. (After König.)
152. Winter and Spring Wheat Flours.—There are two general classes of wheat: spring wheat and winter wheat. The winter varieties are seeded in the fall, and the spring varieties, which are grown mainly in the Northwestern states, Minnesota, and North and South Dakota, and the Canadian Northwest, are seeded in the spring and mature in the late summer. Winter wheat is confined to more southern latitudes and regions of less severe winter, and matures in the early summer. There are many varieties of both spring and winter wheat, although wheats are popularly characterized only as hard or soft, depending upon the physical properties. The winter wheats are, as a rule, more soft and starchy than the spring wheats, which are usually corneous or flinty to different degrees. There is a general tendency for wheats to become either starchy or glutinous, owing to inherited individuality of the seed and to environment. There are often found in the same field wheat plants yielding hard glutinous kernels, and other plants producing starchy kernels containing 5 per cent less proteids. Wheats of low protein content do not make high-grade flour; neither do wheats of the maximum protein content necessarily make the best flour. For a more extended discussion of wheat proteids, the student is referred to Chapter XI.
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
| Water | Per Cent 12.0 | ||
| { | |||
| Ash | Potash Soda Lime Magnesia Phosphoric anhydrid Sulphuric anhydrid Other Substances | Per Cent 2.25 | |
| { | |||
| Protein | Albumin | 0.4 | |
| Globulin | 0.9 | ||
| Gliadin | 6.0 | Per Cent 13.0 | |
| Glutenin | 5.3 | ||
| Other proteids | 0.4 |
| Per Cent | |
| 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 |
