The introduction of the roller process of milling has made it possible to use varieties bf wheat from which high-grade flour could not be made by the old stone process. By the roller process of reduction a portion of the hard granual middlings which were formerly excluded from the flour and sold with the by product used for animal feeding are now re duced and added to the patent grades of flour. About 75 per cent of the cleaned wheat is re turned as merchantable flour, 72 per cent being straight grade or ordinary white flour. In or dinary milling, the grades are as follows: (1) patents; (2) straight, sometimes called stand ard patent; (3) first clear: (4) second clear. Patent flour is the highest grade manufactured. Its gluten has greater power of expansion and absorbs more water than that from any other grade. Patent flour produces the whitest and largest sized loaf of bread. Straight or stand ard patent flour is similar to the patent, but the bread is slightly darker in color and the gluten does not possess quite so high a power of expansion. First clear grade flour is ob tained after the removal of the .first patent grades. This flour is slightly darker. in color and produces a less pleasing loaf than the patent grades. Second clear or low grade is the name given to a small amount of flour ob tained after the removal of the first clear. In some mills about 12 per cent of the cleaned wheat is recovered as first clear flour and about 5 per cent as second clear or low grade. When the wheat is milled so that the patents and the first clear are all obtained as one flour, the product is called straight grade. This is the flour that is extensively used for bread-making purposes. Straight flour is the sum of the patents and the first clear. The lowest grade of flour manufactured is called red dog; it is dark in color and possesses but little power of expansion. It is secured largely from those portions of the wheat kernel adjacent to the germ and aleurone layers. Red dog flour is not generally used for human food, but is em ployed in the arts, for the feeding of animals and occasionally in the preparation of some cereal breakfast food. It has a high per cent of protein or nitrogenous material, but is not valuable for bread-making purposes because the gliadin and glutenin (see BREAD AND BREAD MAKING) are not present in the right propor tions to form a balanced gluten. By blending the different streams of flour, various com mencal grades sold under different trade names are secured. The composition and prop ertiesof different kinds of flour result from the kind of wheat used in preparation (see WHEAT) and the method of milling employed.
The percentage amounts of bran, shorts and standard grades of flour obtained by the roller process vary widely with different kinds of wheat. Some wheats yield more flour than do others. The average yields are approximately as follows: Per cent of cleaned wheat recovered 1. Patent (about) 60 2. Straight or standard patent * 70 to 73 3. First clear or first bakers 10 to 13 4. Second clear or low-grade 0.5 to 3 5. Red dog Il to 2 6. Snorts or middlings II to 12 1. Bran 13 By the roller process of milling, the germ is excluded because of its poor bread-making properties and its fermentable nature. The wheat offals of which shorts and bran form the main portion are by-products used for the feeding of animals. About 25 per cent of the cleaned wheat finds its way into the offals. Bran is the episperm or outer covering of the wheat kernel. As human food, it is indigestible and does not yield as large an amount of available nutrients as the floury part of the wheat kernel. As an animal food, however, it has a high value. Shorts consist mainly of the fine bran mixed with some of the floury portions of the wheat kernel. When the wheat screenings, consisting of weed seeds and other refuse, are ground and mixed with the offal, the product is known as bran or middlings, with ground screenings. From 1.3 to 1.6 per cent of the weight of the cleaned wheat is recovered as germ.
Wheat flour is composed of starch, gluten proteins, water, fat, ash, or mineral matter and small amounts of other compounds, as sugars, cellulose, organic acids, amids, etc. The proximate composition of the different kinds of flour when milled from the same lot of hard wheat is given in the following table: (The two types of patent flour could not be milled at the same time).
From the table, it will be observed that there is a gradual increase in the amount of ash, proteins and fat from the first patent flour to the red dog or lowest grade of flour. In fact, the variations in ash content of the different grades of flour are so regular that the percent age of ash can, at times, be taken as an index to the grade of flour. The highest grade flours,
as first patent, contain least ash because of the more perfect exclusion of the bran and en dosperm parts. In the straight grade or ordi nary bread flour, there is only from .6 to .7 per cent less nitrogenous material as proteins than in the wheat from which it was milled. Second clear and red dog flours contain a large amount of protein, fat and ash, and judged by their proximate composition only, would appear to have a higher nutritive value than the patents or straight grade flours. But when judged on the basis of digestibility, available nutrients and physical character of the bread, these flours are found to have a much lower value than the patents or straight grade flours. (For nutritive values, see article on BREAD AND BREAD MAK ING). During the process of milling, the flour particles pass through bolting cloths containing from 12,000 to 16,000 meshes per square inch, which results in even and fine granulation of the flour particles. The character of the flour particles as angular or spherical depends largely upon the character of the wheat as hard or soft, and to a less extent upon the method of milling. The flour granules from hard wheat are angular and have a sharp feeling akin to fine sand, while soft wheat flours produce small spherical particles lacking in gritty feel ing.
Flours made from strong hard glutinous wheats contain more protein and have a higher food value than those made from soft starchy wheats.
In the testing of flour, particular attention is given to physical characteristics, as color, purity as indicated by absence of dirt and fine pieces of bran, capacity to absorb water, quality of gluten and character of the bread product For bread-making purposes, the quality of the flour depends largely upon the amount and quality of the gluten. The gluten is obtained by making a stiff dough of the flour and then washing this dough with an abundance of water, which removes the starch, leaving the gluten in the form of a gum-like mass. Gluten from high-grade flours is firm, elastic, white or of slightly yellowish tinge and possesses good qualities of expansion. Poor gluten is dark in color, sticky and lacking in elasticity. The color of the flour depends largely upon the quality of the wheat and the method of milling employed. Some wheats produce creamy or yellowish flours, others chalk white flours and others dark-colored flours. Dark-colored flours, however, produce bread of inferior quality, creamy and white flours producing the best grades of bread. The granulation of the flour is also taken as an index of its quality, as it reveals to the experienced miller and baker the character of the flour. Comparative baking tests are generally resorted to in order to determine the bread-making value of flours. By these tests, tinder uniform conditions with the same amount of flour, yeast, water, etc., in each case, differences in the bread-making qualities of the flour are readily revealed. When flour is stored for a long time, it some times becomes inferior through fermentation. Ordinarily, flour will not deteriorate until after it has been kept for many months or more. Some wheats produce flours of better keeling qualities them do others. The soundness of the wheat, as freedom from rust, smut or other blemishes, influences the keeping qualities of flour as well as does also the process of mill ing, particularly the extent to which the clean ing and purification are perfected.
Wheat flour is not ordinarily adulterated, although at times attempts have been made to add other cereals and mineral adulterants. The national flour law requiring all mixed flours to be branded and to pay a slight revenue tax has prevented extensive adulteration. At one time, corn flour produced by milling corn was used for adulterating wheat flour. This, however, was only practised for a very short time when corn was cheap and wheat was high in price. The blending of wheat and corn flours has never proven succes ful as an inferior bread product results, and the practice since tla pass ing of the national flour law has been discon tinued. Wheat flour appears to be less subject to adulteration than many other articles of food. SCe ADULTERATION. • Wheat flour is used not only for bread mak ing but for other purposes. Crackers, cakes, pastry and many food articles are made largely of flour. Flour is also used in the arts and industries and in various manufacturing opera tions. The comparative value of bread made from different kinds of flour, as graham, entire wheat and straight, is discussed in the article