Human Foods and Their Nutritive Value Part 7

There is no difference between yellow and white corn meal so far as nutritive value is concerned.

[Ill.u.s.tration: FIG. 31.--CORN STARCH.]

145. Oat Preparations are characterized by large amounts of both protein and fat. Because of the removal of the hulls, they contain more protein than the original grain. The oat preparations differ little in chemical composition. They all have about 16 per cent of protein, 7 per cent of fat, and 65 per cent of starch, and are richer in ash or mineral matter than other cereals. The main difference is in method of preparation and mechanical composition. Some are partially cooked and then dried. Those costing 7 cents or more per pound do not contain any greater amount of nutritive substance than those purchased in bulk at about half the price. At one time it was believed that oats contained a special alkaloid having a stimulating effect when fed to animals. Recent investigations, however, show that there is no alkaloidal material in oats, and whatever stimulating effect they may have results from the nutrients they contain. Occasionally there is an appreciable amount of cellulose, or fiber, left in the oat preparations, due to imperfect milling. This noticeably lowers the digestibility. Oatmeal requires much longer and more thorough cooking than many other cereals, and it is frequently used as food when not well prepared. Digestion experiments show that when oatmeal is cooked for four hours or more, it is more readily acted upon by the diastase ferment and digested in a shorter time than oatmeal cooked only a half hour.[5] Oatmeal is one of the cheapest sources from which protein is obtained, and when well cooked it can advantageously form an essential part of the ration. Unless thoroughly cooked, the oat preparations do not appear to be quite so completely or easily digested as some of the other cereals.

[Ill.u.s.tration: FIG. 32.--OAT STARCH GRANULES.]

[Ill.u.s.tration: FIG. 33.--WHEAT STARCH GRAINS.]

146. Wheat Preparations differ in chemical composition more than those from oats or corn, because wheat is prepared in a greater variety of ways. They are made either from the entire kernel, including the bran and germ, or from special parts, as the granular middlings, as in the case of some of the breakfast foods, and a few are made into a dough and baked, then dried and toasted. Some special flours are advertised as composed largely of gluten, but only those that have been prepared by was.h.i.+ng out the starch are ent.i.tled to be cla.s.sed as gluten flours.[58]

For the food of persons suffering from diabetes mellitus physicians advise the use of flour low in starch, and this can be made by was.h.i.+ng and thus removing a portion of the starch from wheat flour, as directed in Experiment No. 30. The glutinous residue is then used for preparing articles of food. a.n.a.lyses of some of the so-called gluten flours show that they contain no more gluten than ordinary flour, particularly the low grades. A number of wheat breakfast foods are prepared by sterilizing the flour middlings obtained after removal of the bran and germ. These middlings are the same stock or material from which the patent grades of flour are made, and they differ from wheat flour only in mechanical structure and size of the particles. Where granular wheat middlings can be secured in bulk at the same price as flour they furnish a valuable and cheap cereal breakfast food.

As to the digestibility and food value, the wheat breakfast foods have practically the same as graham, entire wheat, or ordinary patent flour, depending upon the stock which they contain. Those with large amounts of bran and germ are not as completely digested as when these parts of the kernel are not included. Wheat preparations, next to oats, have the most protein of any of the cereal foods. Occasionally they are prepared from wheats low in gluten and not suitable for bread-making purposes. When purchased in bulk the wheat preparations are among the cheapest foods that can be used in the dietary.[56]

[Ill.u.s.tration: FIG. 34.--BARLEY STARCH.]

147. Barley Preparations are not so extensively used as wheat, oats, and corn. Barley contains a little more protein than corn, but not quite so much as wheat; otherwise it is quite similar to wheat in general composition. Sometimes in the preparation of breakfast foods barley meal is mixed with wheat or corn. Barley is supposed to be more readily digested than some of the other cereals, because of the presence of larger amounts of active ferment bodies, and it is frequently used for making an extract known as "barley water," which, although it contains very little nutritive value, as less than one per cent of the weight of the barley is rendered soluble, is useful in its soothing influence and mechanical action upon the mucous membrane of the digestive tract.

[Ill.u.s.tration: FIG. 35.--RICE STARCH.]

148. Rice Preparations.--Rice varies somewhat in composition, but usually contains a slightly lower percentage of protein than corn and also a smaller amount of fat. It is particularly rich in starch, and has the least ash or mineral matter of any of the cereals. In order to make a balanced ration, rice should be supplemented with legumes and other foods rich in proteids. It is a valuable grain, but when used alone it is deficient in protein. Rice is digested with moderate ease, but is not as completely absorbed by the body as other cereals, particularly those prepared by fine grinding or pulverization. Of late years rice culture has been extensively introduced into some of the southern states, and the domestic rice seems to have slightly higher protein content than the imported. Rice contains less protein than other cereals, and the starch grain is of different construction. Rice does not require such prolonged cooking as oatmeal; it needs, however, to be thoroughly cooked.

149. Predigested Foods.[56]

"It is questionable whether it would be of advantage to a healthy person to have his food artificially digested. The body under normal conditions is well adapted to utilize such foods as the ordinary mixed diet provides, among them the carbohydrates from the cereals. Moreover, it is generally believed that for the digestive organs, as for all others of the body, the amount of exercise they are normally fitted to perform is an advantage rather than the reverse. It has been said that 'a well man has no more need of predigested food than a sound man has for crutches.' If the digestive organs are out of order, it may be well to save them work, but troubles of digestion are often very complicated affairs, and the average person rarely has the knowledge needed to prescribe for himself. In general, those who are well should do their own work of digestion, and those who are ill should consult a competent physician."--WOODS AND SNYDER.

150. The Value of Cereals in the Dietary.--Cereals are valuable in the dietary because of the starch and protein they supply, and the heat and energy they yield. They are among the most inexpensive of foods and, when properly prepared, have a high degree of palatability; then, too, they are capable of being blended in various ways with other foods. Some are valuable for their mechanical action in digestion, rather than for any large amount of nutrients. They do not furnish the quant.i.ty of mineral matter and valuable phosphates that is popularly supposed. They all contain from 0.5 to 1.5 percent of mineral matter, of which about one third is phosphoric anhydrid. In discussing the phosphate content of food, Hammersten states:[59]

"Very little is known in regard to the need of phosphates or phosphoric acid.... The extent of this need is most difficult to determine, as the body shows a strong tendency, when increased amounts of phosphorus are introduced, to retain more than is necessary. The need of phosphates is relatively smaller in adults than in young developing animals."

In the coa.r.s.er cereals, which include the bran and germ, there is the maximum amount of mineral matter, but, as in the case of graham bread, it is not as completely digested and absorbed by the body as the more finely granulated products which contain less. The kind of cereal to use in the dietary is largely a matter of personal choice. As only a small amount is usually eaten at a meal, there is little difference in the quant.i.ty of nutrients supplied by the various breakfast cereals.

TOTAL AND DIGESTIBLE NUTRIENTS AND FUEL VALUE OF CEREALS [Transcriber's note: This table has been divided into two parts to fit limits on page width.]

======================================================= | TOTAL NUTRIENTS | |-----+----+----+----------+----+ | | | | C.H. | | KIND OF FOOD |Water|Pro.|Fat +----+-----+Ash | | | | |N.F.|Fiber| | | | | |Ext | | | ----------------------+-----+----+----+----+-----+----+ | % | % | % | % | % | % | Oat Preparations: | | | | | | | Oats, whole grain | 11.0|11.8| 5.0|59.7| 9.5| 3.0| Oatmeal, raw | 7.3|16.1| 7.2|66.6| 9.9| 1.9| Rolled, steam-cooked| 8.2|16.1| 7.4|65.2| 1.3| 1.8| Wheat: | | | | | | | Whole grain | 10.5|11.9| 2.1|71.9| 1.8| 1.8| Cracked wheat | 10.1|11.1| 1.7|73.8| 1.7| 1.6| Rolled, steam-cooked| 10.6|10.2| 1.8|74.4| 1.8| 1.5| Shredded wheat | 8.1|10.6| 1.4|76.6| 2.1| 1.8| Crumbed and malted | 5.6|12.2| 1.0|77.6| 1.7| 1.0| Farina | 10.9|11.0| 1.4|75.9| 0.4| 0.4| Rye: | | | | | | | Whole grain | 11.6|10.6| 1.7|72.5| 1.7| 1.9| Flaked, to be eaten | 11.1|10.0| 1.4| 75.8 | 1.7| raw | | | | | | | Barley: | | | | | | | Whole grain | 10.9|12.4| 1.8|69.8| 2.7| 2.4| Pearled barley | 11.5| 8.5| 1.1|77.5| 0.3| 1.1| Buckwheat: | | | | | | | Flour | 13.6| 6.4| 1.2|77.5| 0.4| 0.9| Corn: | | | | | | | Whole grain | 10.9|10.5| 5.4|69.6| 2.1| 1.5| Corn meal, unbolted | 11.6| 8.4| 4.7| 74.0 | 1.3| Corn meal, bolted | 12.5| 9.2| 1.9|74.4| 1.0| 1.0| Hominy | 10.9| 8.6| 0.6|79.2| 0.4| 0.3| Pop corn, popped | 4.3|10.7| 5.0|77.3| 1.4| 1.3| Hulled corn | 74.1| 2.3| 0.9| 22.2 | 0.5| Rice: | | | | | | | Whole rice, polished| 12.3| 6.9| 0.3| 80.0 | 0.5| Puffed rice | 7.1| 6.2| 0.6| 85.7 | 0.4| Crackers | 6.8|10.7| 8.8|71.4| 0.5| 1.8| Macaroni | 10.3|13.4| 0.9| 74.1 | 1.3| =======================================================

================================================= | DIGESTIBLE NUTRIENTS |----+----+----+----+------ | | | | | Fuel KIND OF FOOD |Pro.|Fat |C.H.|Ash | Value | | | | | per lb.

| | | | | ----------------------+----+----+----+----+---------- | % | % | % | % | Calories.

Oat Preparations: | | | | | Oats, whole grain | -- | -- | -- | -- | -- Oatmeal, raw |12.5| 6.5|65.5| 1.4| 1767 Rolled, steam-cooked|12.5| 6.7|64.5| 1.4| 1759 Wheat: | | | | | Whole grain | -- | -- | -- | -- | -- Cracked wheat | 8.1| 1.5|68.7| 1.2| 1501 Rolled, steam-cooked| 8.5| 1.6|70.7| 1.1| 1541 Shredded wheat | 7.7| 1.3|71.1| 1.4| 1521 Crumbed and malted | 9.1| 0.9|73.7| 1.4| 1623 Farina | 8.9| 1.3|72.9| 0.5| 1609 Rye: | | | | | Whole grain | -- | -- | -- | -- | -- Flaked, to be eaten | 7.8| 1.3|71.1| 1.3| 1516 raw | | | | | Barley: | | | | | Whole grain | -- | -- | -- | -- | -- Pearled barley | 6.6| 1.0|73.0| 0.3| 1514 Buckwheat: | | | | | Flour | 5.0| 1.1|73.1| 0.7| 1471 Corn: | | | | | Whole grain | -- | -- | -- | -- | -- Corn meal, unbolted | 6.2| 4.2|73.2| 1.0| 1728 Corn meal, bolted | 6.8| 1.7|74.6| 0.8| 1602 Hominy | 6.4| 0.5|78.7| 0.2| 1671 Pop corn, popped | 7.9| 4.5|77.8| 1.0| 1882 Hulled corn | 1.7| 0.8|21.8| 0.4| 492 Rice: | | | | | Whole rice, polished| 5.8| 0.3|78.4| 0.4| 1546 Puffed rice | 5.1| 0.5|84.0| 0.3| 1639 Crackers | 9.1| 7.9|70.5| 1.4| 1905 Macaroni |11.6| 0.8|72.2| 1.0| 1660 =================================================

CHAPTER X

WHEAT FLOUR

151. Use for Bread Making.--Wheat is particularly adapted to bread-making purposes because of the physical properties of the gliadin, one of its proteids. It is the gliadin which, when wet, binds together the flour particles, enabling the gas generated during bread making to be retained, and the loaf to expand and become porous. Wheat varies in chemical composition between wide limits; it may contain as high as 16 per cent of protein, or as low as 8 per cent; average wheat has from 12 to 14 per cent; and with these differences in composition, the bread-making value varies.

[Ill.u.s.tration: FIG. 36.--STARCHY (LIGHT-COLORED) AND GLUTINOUS (DARK-COLORED) WHEATS.]

152. Winter and Spring Wheat Flours.--There are two general cla.s.ses 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 lat.i.tudes 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.

[Ill.u.s.tration: FIG. 37.--LONGITUDINAL SECTION OF WHEAT KERNEL: _a_, pericarp; _b_, bran layers; _c_, aleurone cells; _d_, germ. (After KoNIG.)]

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

======================================================== | Per Cent Water | 12.00 | {Potash } | {Soda } | {Lime } | Ash {Magnesia } | 2.25 {Phosphoric anhydrid} | {Sulphuric anhydrid } | {Other substances } | | {Alb.u.min 0.4} | {Globulin 0.9} | Protein {Gliadin 6.0} | 13.00 {Glutenin 5.3} | {Other proteids 0.4} | 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 =======================================================

154. Roller Process of Flour Milling.--Flours vary in composition, food value, and bread-making qualities with the character of the wheat and the process of milling employed. Prior to 1870 practically all wheat flour was prepared by grinding the wheat between millstones; but with the introduction of the roller process, steel rolls were subst.i.tuted for millstones.[60] By the former process a smaller amount of flour was secured from the wheat, but with the present improved systems about 75 per cent of the weight of the grain is recovered as merchantable flour and 25 per cent as wheat offals, bran, and shorts[61].

[Ill.u.s.tration: FIG. 38.--GRANULAR WHEAT FLOUR PARTICLES.]

The wheat is first screened and cleaned, then pa.s.sed on to the corrugated rolls, or the first break, where it is partially flattened and slightly crushed and a small amount of flour, known as the break flour, is separated by means of sieves, while the main portion is conveyed through elevators to the second break, where the kernels are more completely flattened and the granular flour particles are partially separated from the bran. The material pa.s.ses over several pairs of rolls or breaks, each succeeding pair being set a little nearer together. This is called the gradual reduction process, because the wheat is not made into flour in one operation. More complete removal of the bran and other impurities from the middlings is effected by means of sieves, aspirators, and other devices, and the purified middlings are then pa.s.sed on to smooth rolls, where the granulation is completed. The flour finally pa.s.ses through silk bolting cloths, containing upwards of 12,000 meshes per square inch. The dust and fine debris particles are removed at various points in the process. The granulation of the middlings is done after the impurities are removed, the object being first to separate as perfectly as possible the middlings from the branny portions of the kernel. If the wheat were first ground into a fine meal, it would be impossible to secure complete separation of the flour from the offal portions of the kernel.

[Ill.u.s.tration: FIG. 39.--EXTERIOR OF FLOUR MILL AND WHEAT ELEVATOR.]

Flour milling is entirely a mechanical process; the flour stock pa.s.ses from roll to roll by means of elevators. According to the number of reductions which the middlings and stock undergo, the milling is designated as a long or a short reduction system; the term 4, 6, 8, or 10 break process means that the stock has been subjected to that number of reductions. With an 8-break system of milling, the process is more gradual than with a 4-break, and greater opportunity is afforded for complete removal of the bran. In some large flour mills, the wheat is separated into forty or more different products, or streams, as they are called, so as to secure a better granulation and more complete removal of the offals, after which many of these streams are brought together to form the finished flour. What is known as patent flour is derived from the reduction of the middlings, while the break flours are recovered before the offals are completely removed; hence they are not of so high a grade. No absolute definition can be given, however, of the term "patent flour," as usage varies the meaning in different parts of the country.

155. Grades of Flour.--Flour is the purified, refined, and bolted product obtained by reduction and granulation of wheat during and after the removal of the branny portions of the wheat kernel. It is defined by proclamation of the Secretary of Agriculture, under authority of an act of Congress, as: "Flour is the fine, sound product made by bolting wheat meal, and contains not more than thirteen and one half (13.5) per cent of moisture, not less than one and twenty-five hundredths (1.25) per cent of nitrogen, not more than one (1) per cent of ash, and not more than fifty hundredths (0.50) per cent of fiber."

[Ill.u.s.tration: FIG. 40.--GRINDING FLOOR OF FLOUR MILL, RUSSELL-MILLER MILLING CO., MINNEAPOLIS, MINN.]

Generally speaking, flour may be divided into two cla.s.ses, high grade and low grade. To the first cla.s.s 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 cla.s.s 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 debris 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.

[Ill.u.s.tration: FIG. 41.--SILK BOLTING CLOTH USED IN MANUFACTURE OF FLOUR, MAGNIFIED.]

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

=========================================================================== |WATER| PROTEIN | FAT| CARBO-| ASH| ACIDITY | HEAT OF MILLED PRODUCT | |(N 5.7)| | HY- | | CALCUL- |COMBUSTION | | | | DRATES| |ATED AS | PER GRAM | | | | | |LACTIC |DETERMINED | | | | | | ACID | --------------------------------------------------------------------------- | % | % | % | % | % | % |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 |10.54| 11.99 |1.61| 75.36 |0.50| 0.09 | 4050 flour | | | | | | | First clear grade |10.13| 13.74 |2.20| 73.13 |0.80| 0.12 | 4097 flour | | | | | | | Second clear grade |10.08| 15.03 |3.77| 69.37 |1.75| 0.56 | 4267 flour | | | | | | | "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 ===========================================================================

[Footnote 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 const.i.tuent. 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 coa.r.s.ely granulated wheat meal. No sieves or bolting cloths are employed in its manufacture, and many coa.r.s.e, unpulverized particles are present in the product[62].