kernels are softer and more starchy, is more easily separated from the husk than the spring wheat, whose kernel is much harder and much richer in gluten. The richer the wheat, the more difficult becomes the process of separating it from the husk, because the gluten is itself the cause of the toughness. Hence winter wheat produces a much whiter flour than spring wheat when both are ground by millstones. But in order to produce a white flour from either kind of wheat a large portion of the middlings, being inseparable from the bran, is lost. Hence the problem how to save and purify the middlings is a vital one with millers. While the old process aimed to avoid middlings as entailing loss of flour, the new process seeks to produce middlings, because out of the middlings comes the high-grade flour and the gluten which gives flour its rising power is saved.
The machines called ‘middlings purifiers,’ for winnowing the wheat between the successive grindings, are of two general types, the gravity and sieve purifiers. In the gravity purifiers, which are used for the larger-sized grains, the middlings pass in a thin stream through a current of air produced by a revolving fan, and so regulated that the bran is blown away while the wheat, being heavier, drops down into a receptacle. The sieve is an oscillating strainer of gauze, through which a current of air passes outward, carrying off the bran, while the wheat passes through the sieve. Many of the middlings purifiers in use are quite complicated in their structure, but the general principles upon which they operate are as described above.
Grades of Flour. Three grades of process flour are on the market: High-grade patent flour, baker's flour, and low-grade flour. One hundred pounds of good wheat produces about 76 pounds of all grades, and of these 72 to 76 per cent. is high grade and 18 to 22 per cent. baker's, the remainder being low grade. The accompanying table, compiled from figures published in the Year Book of the Department of Agriculture (1897), shows the comparative food values contained in different grades of flour, while the ash, fibre, and water represent waste. The four flours given in the table are the high-grade patent flour, baker's flour, common market flour, and flour of small mills, the samples being procured by regular purchase in the markets of Washington:
Food Values of Different Grades of Flour
| High grade patent flour |
Bakers' flour |
Common market flour |
Flour of small mills | |
| Water | 12.75 | 11.75 | 12.25 | 12.85 |
| Proteids | 10.50 | 12.30 | 10.20 | 10.30 |
| Ether extract | 1.00 | 1.30 | 1.30 | 1.05 |
| Ash | .50 | .60 | .90[1] | .50 |
| Moist gluten | 26.00 | 34.70 | 24.50 | 26.80 |
| Dry gluten | 10.00 | 13.10 | 9.25 | 10.20 |
| Carbohydrates | 75.25 | 74.05 | 75.65 | 75.30 |
Various attempts have been made from time to time to produce a flour which should contain all the nutritive elements of the wheat, and still be palatable and digestible. Perhaps the earliest and best-known of these is graham flour, so called introduced by Dr. Graham. This contains not only all the wheat, but the husk as well. It is coarse in texture, and, on account of the large amount of indigestible husk, irritating to some stomachs. Later the so-called whole-wheat or entire-wheat flours were brought upon the market, a much finer product, with more or less of the husk excluded. Gluten flours, from which the starch has been almost entirely excluded, have also been manufactured, and are valuable in certain forms of dyspepsia, where there is an inability to digest starch.
Self-Raising Flour. This is simply a flour into which has been mixed some chemical leavening agent, such as an ordinary baking-powder, or its constituents. This is possible, because bicarbonate of soda and tartaric acid, for instance, do not combine to produce carbonic-acid gas except in the presence of moisture. In the Year Book of the Department of Agriculture for 1897 analyses are given of a typical self-raising flour and of the common brands of flour, as offered for sale in open market at Washington. From these the following comparative table has been prepared:
| CONSTITUENTS | Self-raising flour |
High-grade patent |
Bakers' |
| Water | 12.30 | 12.75 | 11.75 |
| Proteids (factor 6.25) | 10.10 | 10.50 | 12.30 |
| Moist gluten | 27.00 | 26.00 | 34.70 |
| Dry gluten | 9.65 | 10.00 | 13.10 |
| Ether extract | .70 | 1.00 | 1.30 |
| Ash | 4.00 | .50 | .60 |
| Carbohydrates | 72.90 | 75.25 | 74.99 |
Now, as the ash represents waste, the significant fact in this table is the relatively large amount of ash in the prepared flour, there being an excess of 3.5 per cent.
Flour Manufacture in the United States. In Colonial days large quantities of wheat were raised and converted into flour in America; but with the Hessian soldiers of the Revolution was imported the Hessian fly, a scourge which literally drove the production of wheat across the Alleghanies. Since that time the centre of wheat and flour production has steadily moved to the Northwest. In 1815 a steam flour-mill, having a capacity of 700 barrels per week, was built at Cincinnati. The first merchant mill in Minneapolis was erected in 1854. During the last half-century the importance of the latter city as a milling centre has increased so rapidly that it now ranks first in the world as a producer of flour. With the new process of flour manufacture came the era of the big flour-mill. This was due partly to the fact that the machinery involved is too complicated and expensive for the small manufacturer, and partly because this change is simply in line with modern industrial development. In the bulletin on flouring and grist-mill products of the U. S. census of 1900 a distinction is made between merchant and customs mills, and from the statistics given it is evident that milling on a small scale is still a flourishing industry. Customs mills are defined in this report as mills grinding wheat, corn, and other grain furnished from farms in the neighborhood, and are usually denominated grist-mills. Merchant mills are large manufacturing establishments supplying the home market, and exporting flour to the principal foreign countries. In mere numbers the customs or exchange mills constitute 59 per cent. of the total number of milling establishments. The largest number of small mills was found in Pennsylvania, and of mills of the greatest ca-
- ↑ And fibre.
