Fig. 41.—Silk Bolting
Cloth Used in Manufacture
of Flour, Magnified.
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 débris 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.
156. Composition of Flour.—The composition of the different grades of flour made from the same wheat is given in the following table:[[62]]
Composition, Acidity, and Heats of Combustion of Flours And Other Milled Products of Wheat
| Milled Product | Water | Protein (N × 5.7) | Fat | Carbohydrates | Ash | Acidity calcualted as Lactic Acid | Heat of Combustion Per Gram Determined |
|---|---|---|---|---|---|---|---|
| % | % | % | % | % | % | Calories | |
| First patent flour | 10.55 | 11.08 | 1.15 | 76.85 | 0.37 | 0.08 | 4032 |
| Second patent flour | 10.49 | 11.14 | 1.20 | 76.75 | 0.42 | 0.08 | 4006 |
| Straight[A] or standard patent flour | 10.54 | 11.99 | 1.61 | 75.36 | 0.50 | 0.09 | 4050 |
| First clear grade flour | 10.13 | 13.74 | 2.20 | 73.13 | 0.80 | 0.12 | 4097 |
| Second clear grade flour | 10.08 | 15.03 | 3.77 | 69.37 | 1.75 | 0.56 | 4267 |
| "Red dog" flour | 9.17 | 18.98 | 7.00 | 61.37 | 3.48 | 0.59 | 4485 |
| Shorts | 8.73 | 14.87 | 6.37 | 65.47 | 4.56 | 0.14 | 4414 |
| Bran | 9.99 | 14.02 | 4.39 | 65.54 | 6.06 | 0.23 | 4198 |
| Entire-wheat flour | 10.81 | 12.26 | 2.24 | 73.67 | 1.02 | 0.32 | 4032 |
| Graham flour | 8.61 | 12.65 | 2.44 | 74.58 | 1.72 | 0.18 | 4148 |
| Wheat | 8.50 | 12.65 | 2.36 | 74.69 | 1.80 | 0.18 | 4140 |
[A] Straight flour includes the first and second patents and first clear grade.
In the table it will be noted that there is a gradual increase in protein content from first patent to "red dog," the largest amount being in the "red dog" flour. Although "red dog" contains the most protein, it is by far the poorest flour in bread-making qualities, and in the milling of wheat often it is not separated from the offals, but is sold as an animal food. It will also be seen that there is a gradual increase in the ash content from the highest to the lowest grades of flour, the increase being practically proportional to the grade,—the most ash being in the lowest grade. The grade to which a flour belongs can be determined more accurately from the ash content than from any other constituent. Patent grades of flour rarely contain more than 0.55 per cent of ash,—the better grades less than 0.5 per cent. The more completely the bran and offals are removed during the process of milling, the lower the per cent of ash. The ash content, however, cannot be taken as an absolute guide in all cases, as noticeable variations occur in the amount of mineral matter or ash in different wheats; starchy wheats that have reached full maturity often contain less than hard wheats grown upon rich soil where the growing season has been short, and from such wheats a soft, straight flour may have as low a per cent of ash as a hard first patent flour. When only straight or standard patent flour is manufactured by a mill, all of the flour is included which would otherwise be designated first and second patents and first clear.
157. Graham and Entire Wheat Flours.—When the germ and a portion of the bran are retained in the flour, and the particles are not completely reduced, the product is called "entire wheat flour." The name does not accurately describe the product, as it includes all of the flour and only a portion of the bran, and not the entire wheat kernel. Graham flour is coarsely granulated wheat meal. No sieves or bolting cloths are employed in its manufacture, and many coarse, unpulverized particles are present in the product[[62]].
158. Composition of Wheat Offals.—Bran and shorts are characterized by a high percentage of fiber, or cellulose. The ash, fat, and protein content of bran are all larger than of flour. The protein, however, is not in the form of gluten, but is largely albumin and globulins,[[16]] which are mainly in the aleurone layer of the wheat kernel, and are inclosed in branny capsules, and consequently are in a form not readily digested by man.