This section is from the book "Experimental Cookery From The Chemical And Physical Standpoint", by Belle Lowe. Also available from Amazon: Experimental cookery.
In separating the endosperm from the rest of the wheat berry and reducing it to flour, some small bran particles are broken from the bran coats. As these particles are formed they are separated from the flour stock and may be graded according to size and included in the various feeds. As it is impossible to prevent some flour particles' being removed with the bran, these flour particles may also be graded according to size and may become part of the feeds. The other portions into which the wheat berry may be separated, in order as the percentage of bran particles increases, are First Clear, Second Clear, Red Dog, Flour Middlings, Shorts, and Bran.
Classes of wheats used for flour. Wheats are classified in five main groups as follows: (1) white, (2) hard red spring, (3) hard red winter, (4) soft red winter, and (5) durum. Since the composition of the wheat varies with climatic and soil conditions to which it has been subjected in growing, it is natural that many variations in composition occur within each class. The sections in which the different classes of wheat are grown overlap to a greater or less degree. The major portion of the hard red spring wheat and durum wheat is grown in the North Central States of the United States and in Canada, whereas hard red winter wheat is grown chiefly in the South Central and Middle Central States. This class of wheat leads all others grown in Iowa, Nebraska, Kansas, Oklahoma, Texas, and Colorado. At present twice as much acreage is planted in hard red winter wheat as in any other class of wheat. Soft red winter wheat is grown in Missouri and the eastern half of the United States. It is also grown in some Western States, particularly Oregon, Washington, and Idaho. White wheat is grown to a limited extent in the northeastern part of the United States and in Michigan, New York, and on the Pacific Coast.
Flour terminology. Flour terminology had become confusing but as a result of the work of the committee on terminology of the Millers' National Federation, in cooperation with the U. S. Department of Agriculture, definitions for labeling have been worked out and progress has been made in clarifying the terminology. It has been suggested that grade be used to refer to the type of flour as determined by the milling process, whereas the word class be used to designate the kind of wheat from which the flour is milled. According to such a plan, grades of flour would be patent, clear, etc.; classes would be durum, hard- and soft-wheat flours.
Definition of flour. The definition of flour is from the Definitions and Standards for Food Products of the Service and Regulatory Announcements of the U. S. Department of Agriculture, issue of 1933.
"Whole-wheat flour, entire-wheat flour, graham flour, is the product made by grinding wheat, and contains, in their natural proportions, all of the constituents of the cleaned grain."
Harrell and Benson state that whole-wheat flour may be of coarse, medium, or fine granulation.
"Flour, wheat flour, white flour, is the fine-ground product obtained in the commercial milling of wheat, and consists essentially of the starch and gluten of the endosperm. It contains not more than 15 per cent moisture, not less than 1 per cent nitrogen, not more than 1 per cent ash, and not more than 0.5 per cent fiber."
Straight flour. Straight flour (100% flour) is a milling term indicating that all the bolted wheat meal has been recovered from the wheat after removal of the feeds. It is not generally on the market and all commercial flours are derived from straight flour.
Patent flour. Patent flour may be made from any class of wheat and is the more refined portion of the wheat meal from which all or a portion of the clears have been removed. (How "long" or "short" a patent is depends on how much of the total flour is included. In general, most patent flours include about 85 per cent of the total flour obtained from the wheat. But a very "short" patent used in fancy cake flour may include only 25 per cent of the total flour.)
Clear flour. Clear flour is the less refined bolted portion of the wheat meal recovered in the manufacture of Patent flour. According to trade practise or demand, clear flour may be divided into First and/or Second Clears.
First Clear is the better portion of the Clear when separated into two parts.
Second Clear is the remaining portion of the Clears when First Clear is removed.
The purpose for which the flour is intended. Hard-wheat flours. Practically all durum wheat is used for the manufacture of semolina, which in turn is used for macaroni products.
In general bread flours are made from hard wheats, although suitable soft-wheat flour is used for baking bread in some sections. Bread flour is a term indicating a "strong" flour that has the capacity to make loaves of good volume texture and grain. The term "strong" indicates that the gluten has tenacity, cohesiveness, and elasticity. Bread flour usually contains more gluten and less starch, and the granulation is usually coarser than in either pastry or cake flour.
All-purpose, General-purpose, or Family flour are synonymous terms used for a flour which is suitable for most kinds of baking. It may or may not be a blended flour. It may have as a basis either hard- or soft-wheat flour. Hence, there are two types of all-purpose flours, and which is obtainable in a certain section depends on whether hard or soft wheat predominates in that section.
Soft-wheat flours. Since soft wheats usually contain a smaller quantity of gluten than hard wheats, the flours from these wheats are generally more desirable, and particularly if the gluten is of fine quality, for cakes and pastry products than hard-wheat flours.
Pastry flour is a term indicating a flour usually milled from soft wheat, which is of fine granulation and has a low or moderate amount of gluten. It differs in baking quality from both bread and cake flours.
Cake flour is milled from soft wheat. It is a "short" patent. The granulation is very fine and uniform, the protein content is low but may be of fine quality. Cake flours are usually better grades of flour than pastry flours.
Cracker flour is milled from soft winter wheat. Micka states that because it constitutes nearly 90 per cent of the cracker it is largely responsible for the general character of the finished product. A desirable cracker flour differs from bread flour in color, absorption, and fermentation capacities. Because of the long fermentation period the inside color of crackers is quite uniform but the color of the flour affects the outside color and bloom of the cracker. A cracker flour has a lower water-absorbing capacity than bread flour and, since little sugar is added, the flour must itself furnish the necessary fermentative material.
The geographical areas in which the different classes of wheat are grown determine to a great extent the type of flour that predominates in local retail markets in these areas. For example, in Iowa it is very difficult to obtain soft-wheat flour, except in the specially prepared cake flours, the bread and all-purpose hard-wheat flours being found on the local markets. In Alabama it is just as difficult to obtain hard-wheat flours. In some sections or states both soft- and hard-wheat flours are readily obtainable.
Bleaching of flour. Bleaching can occur through aging or gradual oxidation of the carotene, but a large portion of flour is bleached at the mills in a short time. Nitrogen peroxide or chlorine, benzoyl peroxide or nitrogen trichloride, or a combination of two of these, is used for bleaching.