Foods and Their Adulteration / Origin, Manufacture, and Composition of Food Products; Description of Common Adulterations, Food Standards, and National Food Laws and Regulations

Adulterations.

—There are very few adulterations of oatmeal. Fortunately the price of this cereal is such that the admixture of other cereals would not be profitable. Doubtless such admixtures have often been made but evidently, from the examination of the products upon the open market, they are not very frequent. The characteristic appearance of oat starch is shown in Fig. 29.

Oat starch grains average about 10 microns in diameter. There are usually present some grains of somewhat oval shape, which assist in identifying oat products when present. The starch granules also have a tendency to agglutinate into masses of varying size, as shown in the photograph.

Detection of Adulterations.

—The adulteration of oatmeal with the flour of other cereals can easily be detected by the use of the microscope. Oat starch when highly magnified presents a peculiar cellular structure of pentagonal character which might be compared to the effect produced by grinding a large number of faces upon a precious stone. This peculiar appearance is caused by the tendency of the starch granules in oats to become compacted in large masses. The appearance of the separate granules and also the compact aggregate are shown in the figure on the preceding page. The large aggregated masses are of different sizes, ranging from .02 to 1.2 millimeters in length. These masses are usually broken up by grinding or pressure and, therefore, are not found in very great abundance in the commercial oatmeal. When separated into single granules these are found to be irregular in outline, due to the compression to which they have been subjected, more or less pentagonal in structure, and from .015 to .02 millimeter in diameter. The starch granules do not show any very marked characteristics under polarized light and have neither lines nor hilum. The above statements can easily be verified by any one who can operate an ordinary microscope, but before attempting to detect adulteration a careful examination of starch granules, prepared by the investigator himself, should be made.

RICE (Oryza sativa).

Rice is one of the most important food cereals. It furnishes a large part of the food of the inhabitants of China and Japan. It is a food rich in starch and poor in protein, and furnishes, therefore, heat and energy, and is well adapted for the nourishment of those engaged in hard labor or who undergo extreme physical exertion. The cultivation of rice is rapidly extending in the United States, especially in Louisiana and Texas. The statistical data relating to the rice crop for 1906 are as follows:

The adulteration of rice is confined to coating it with talc, paraffin, and glucose. The object of this treatment is to give a better appearance to the grain and to protect it from the ravages of insects. The use of indigestible substances such as talc and paraffin is scarcely justifiable. The starch granules of rice have distinctive properties which enable them to be readily recognized under the microscope, as shown in Fig. 30.

The rice starch grains are polygonal in form and have sharp angles. The grains vary in size from 2 to 10 microns, though the latter size is seldom reached, the most of the grains being about 6 microns. The hilum is seldom visible. The grains occur in the rice kernels mostly in groups of a considerable number of the individual grains forming starch masses of ovoid or angular form.

RYE.

This is the source of the principal supply of bread in many European countries, but is not extensively used in the United States except among our citizens of foreign birth. It is also extensively used for making whisky. Rye belongs to the genus Secale. Only one species (Secale cereale L.) is commonly cultivated, but this species has a great many different varieties or races. According to the time of sowing there are two great classes of rye, namely, that planted in the autumn or early winter and that planted in the early spring, generally known respectively as winter and spring rye. This is one of the hardiest of cereals, and grows well in all locations where wheat and other common cereals flourish. The area planted in rye in the United States in 1906 and the quantity harvested are given in the following table:

Composition of Rye.

—From a study of many hundreds of analyses of rye of American origin the following table may be given as approximating the composition of a typical American rye:

The percentage of moisture in American grown rye is usually less than that of European origin. The American rye, also, has smaller kernels as a rule than that of foreign growth. In the content of protein the American samples of rye are fully equivalent to those of foreign origin, and in their mean composition, except as noted above, do not differ greatly from that of standard varieties collected abroad.

Protein of Rye.

—As is the case with other cereals more than one nitrogenous constituent exists in the rye. Three of the principal ones have been separated and named as follows: leucosin, gliadin, and edestin. Other proteins belonging to the globulin, albumin, and proteose family are also found in small proportions. The gliadin of rye resembles in its chemical and physical properties the gliadin of wheat. There is, however, in the rye no protein compound corresponding to the glutenin of wheat, and, therefore, rye flour does not form a gluten similar in quality to that of wheat, although it comes more nearly doing so than any other cereal. The gliadin of rye is soluble in alcohol, the leucosin of rye is soluble in water, and the edestin is soluble in a salt solution.

In a typical sample of American rye there will be found about 5.16 percent of gliadin, 2.27 percent of edestin and proteose, 0.55 percent of leucosin, and 3.14 percent of protein soluble in salt solution.

Adulteration of Rye Flour.

—Rye flour is frequently adulterated by the admixture of flours of other cereals. Real rye flour is distinguished by the character of the starch granules, as shown in Fig. 31.

Rye starch grains are lenticular in form, and the largest grains are of about 50 microns diameter. They average somewhat larger than wheat starch grains and are characterized by many of the large grains having a fissure in the form of a slit, cross, or star, which is rare in wheat and barley. The rings and hilum are indistinctly seen in some of the grains.

Rye Bread.

—This bread may be made leavened or unleavened, since the analogy in the property of its protein to that of wheat renders the leavening of rye bread somewhat more easy of accomplishment than that of the other cereals, with the exception of wheat.

Rye bread made of pure rye flour has a dark color, sometimes almost black. It is often baked long in advance of the time of eating and keeps well, is highly nutritious, and is the staple bread of many European countries.

A partial rye flour bread is made by mixing rye flour with other flours, such as wheat, barley, Indian corn, etc., and this is the kind which is commonly used in this country and in many portions of Europe where the light-colored breads are preferred to the dark.

The large consumption of bread made from rye and Indian corn indicates that even if the supply of wheat should become limited there is no reason to fear a famine of bread. It would be easy to substitute bread made wholly or in part of Indian corn and rye for that made wholly of wheat and thus to supply practically any demand for bread which the increasing population of the earth may make.

WHEAT (Genus Triticum).

In respect of human nutrition wheat is the most important of the cereals. It is grown in the temperate regions of almost every country, but does not flourish in tropical or subtropical countries.

In the United States the wheat is divided in respect of the period of its growth into two great classes, namely, winter or fall planted wheat and spring or spring planted wheat. Winter wheat is usually planted from September to November and spring wheat from the last of March to the last of April.

In this country wheat is not cultivated, that is, there is no cultivation of the soil after seeding. The soil is, however, plowed and harrowed before planting. In the winter wheat regions the harvesting is in the month of June, though in the southern localities it comes somewhat earlier and in the more northern localities may extend into July. In the spring wheat regions the harvesting is from the last of July to the middle or end of August. The statistics of wheat grown in the United States during 1906 are as follows:

All the different varieties of wheat which are now known are cultivated. The simplest form, namely, the one grain wheat is the only one which grows wild, and the origin of the other varieties of wheat is unknown.

Botanists recognize three species, namely—Species 1, one grain wheat (Triticum monococcum Lam.); species 2, Polish wheat (Triticum polonicum L.); species 3, common wheat (Triticum sativum Lam.). All of these species are distinct, especially the third one, of which the most valuable variety is the common wheat, Triticum vulgare Vill.

The quality and properties of wheat depend more upon the environment in which it is grown than upon the species to which it belongs. There is perhaps no other field crop in which the environment, namely, condition of the soil, temperature, precipitation, etc., makes a greater difference than in wheat. In general, the environment and the species together produce two kinds of wheat as far as milling and bread making are concerned, namely, the soft or starchy wheat and the hard or glutinous wheat. In the first variety there is a larger percentage of starch in relation to the content or protein matter than in the second. Taking the wheat as a whole its average composition is shown in the following table:

In regard to protein American wheat, as a rule, is quite equal to that of foreign origin. This is an important characteristic when it is remembered that both the milling and food value of a wheat depend largely upon the nitrogenous matter which is present. It must not be forgotten, however, that merely a good percentage of protein is not of itself a sure indication of the milling value of a wheat. The ratio of gluten to the other protein constituents in a wheat is not always constant, but it is the gluten content of a flour on which the bread making qualities chiefly depend.

Gluten.

—The principal part of the protein in wheat is known as gluten. Gluten as such does not exist in the wheat but is formed when the pulverized wheat, that is, the wheat flour, is mixed with water by the union of two elements in the wheat, namely, gliadin, which is soluble in dilute alcohol and forms nearly half of the whole protein matter of the wheat kernel, and glutenin, a compound insoluble in water, dilute salt solutions, and dilute alcohol and which is quite as abundant as gliadin in the wheat kernel. In fact, the gliadin and the glutenin together make the whole of the protein, except a little over one per cent.

There are three other forms of protein, as pointed out by Osborne, in the wheat kernel, making altogether nearly 1¹⁄₂ percent of total protein content. The average quantity of these compounds in the protein of wheat is as follows.

Constituents:

Starch in the Wheat Kernel.

—The most abundant constituent of the wheat kernel is the starch. The appearance of wheat starch is shown in the figure. Wheat starch grains ordinarily show the rings and hilum in a few cases only under the most favorable conditions, though there are sometimes cases where the striations are quite distinct. The granules of starch vary greatly in size, being from 5 to 10 microns in diameter. There are, in fact, two kinds of granules in wheat starch, one having the appearance under the microscope of irregularly rounded particles in sections like a circular disk, and the other of elongated particles with a distinct hilum, as shown in Fig. 32. The appearance of the granules under polarized light is shown in Fig. 33.

Wheat starch is not very commonly used for commercial purposes but is highly prized for some things, especially in the sizing of textile fabrics. The germ in wheat is particularly rich in oil and the bran or outside covering in protein. The common idea that the bran is composed mostly of silicious matter is wholly erroneous. On the contrary the bran is a highly nutritious food, and the objection to it for human food is mostly of a mechanical nature.

Adulterations.

—Wheat grains are never adulterated but they may sometimes contain dirt and foreign seeds, due to the growth of some body in connection with the wheat itself.

Standards.

—Wheat, commercially, is sold under three standards, namely, one, two, three. The difference is an arbitrary one and not founded upon any chemical data but wholly upon the physical appearance, degree of moisture, and freedom from extraneous admixtures.

Wheat Products.

—The principal product of wheat is flour. The milling process for wheat is highly interesting both from a chemical and technical point of view, but cannot be described in full in this manual. The old-fashioned milling of wheat, namely, pressing between stones and separation of the flour by bolting has been almost entirely superseded by the modern milling with metal rollers.

Altogether nearly a hundred different products are made incident or final to the milling of wheat. Only those products, however, which are used for human food interest us at the present time.

Chief Varieties of Flour.

—The highest grade of wheat flour is known usually by the term “patent”; a lower grade is known as “bakers’ flour” and a third as low grade flour. A barrel of flour weighs 196 pounds and requires about 258 pounds of wheat for its manufacture. The whole product from the 258.35 pounds of wheat is shown in the appended table.

In general it may be said that about 75 percent of the weight of the wheat is obtained as merchantable flour of some kind, about 60 to 70 percent being good grade or straight flour. About 24 percent of the weight of the wheat is obtained as cattle food and about 1 percent is lost during the process of manufacture.

Special Names of Flour.

—In addition to the classification above mentioned other names are used in many commercial senses for flour. These additional names are “family,” “red dog,” “blended,” gluten, etc. Many flours are also named after the name of the mill or locality or bear simply fanciful names.

Graham Flour.

—This term was originally applied to the coarse, unbolted flour which was made by grinding the whole wheat. The name, therefore, should be applied to all flour made from well grained wheat, ground, and unbolted. Most of the flours however, which are sold nowadays as graham flours are produced by a more or less perfect bolting process. From the above it is seen that true graham flour will contain practically the same constituents as the wheat kernel itself and in the same proportion and have the same composition as wheat.

Entire Wheat Flour.

—This name would naturally carry the idea of a flour corresponding to the graham flour above mentioned. It is, however, a misnamed trade-mark for a flour produced in a special manner which consists in the removal of the outer or purely branny covering of the grain. “Entire wheat” flour, therefore, contains all the ingredients of wheat grains, save those which are found in the outer branny covering.

Gluten Flour.

—This is a name applied to a flour which is produced by removing the greater part of the starch from ordinary flour. It is especially recommended for the use of diabetic patients. Unfortunately, the name is very commonly applied to flours made from wheat containing a little higher percentage of protein than the ordinary and sometimes even to an ordinary wheat flour. Its use with such a product is purely fraudulent.

Mixed Flour.

—The act of Congress of June 13, 1898, defines mixed flour and imposes a tax upon the manufacture, sale, importation, and exportation of that article. The maximum tax laid upon mixed flour is 4 cents on a barrel of 196 pounds. The total number of barrels of mixed flour returned for taxation for the fiscal year ending June 30, 1905, was 362; half barrels, 59,443; quarter barrels, 6,265; eighth barrels, 24,974. The total quantity of mixed flour returned for taxation during the year is 5,495,937 pounds. The above data show that the amount of mixed flour offered for sale is a very small part of the total flour manufactured in the United States. It may be that there is a great deal of flour mixed and sold in violation of the law since it is quite impossible in the inspection of the stores to supervise all the transactions of business deals in flour; especially is it believed that rye flour and buckwheat flour are often adulterated by mixing with them the flour of other cereals. This adulteration is not one which is at all injurious to health but is simply practiced for the purpose of making a rye or buckwheat flour look whiter or because the added flours are cheaper than the real rye or buckwheat.

Properties Affecting the Commercial Value of Flour.

—Aside from its nutritive properties wheat flour has a commercial value depending upon its color and texture and upon the gluten which it contains. The character of gluten also varies largely in different varieties of wheat and in wheat grown in different localities. A chemical examination will not always tell the bread making properties of a flour, and the character of the bread itself depends often quite as much upon the skill of the baker as upon the flour which is used.

In cases where loaves are sold by weight, a flour with a high percentage of tenacious gluten is often preferred, since it permits of the forming of loaves containing a maximum percentage of water. With a flour rich in gluten it is not difficult to make a palatable loaf which does not bear any evidence of an excess of water, containing as much as 40 percent of moisture. The baking of bread is an art which is most successfully practiced by professionals, and the American method of home bread making does not always lead to the happiest results.

The ideal flour for bread making is one which contains a sufficient quantity of gluten to make a porous and spongy loaf, but not one which permits an excessive quantity of moisture to be incorporated in the loaf itself.

Average Composition of Different Varieties of Flour.

—Analyses of a great number of samples of different varieties of flours lead to the following data, which may be accepted as a very close approximation of the average variety of different grades of flour offered upon the American market:

Separation of Gluten.

—The character of a wheat flour, as has already been intimated, is measured largely by the quantity of gluten which it may contain. The separation of gluten may be accomplished by any one, even without a chemical training, by a little practice. It is, therefore, one of the tests for the value of a wheat flour which can be easily and generally applied. The principle of separation of the gluten rests upon the fact that when wheat flour is moistened and kneaded into a sticky mass it may be washed with pure water with constant kneading until nearly all the starch has been removed from the mass. Meanwhile only that portion of the protein is removed which is soluble in the water and the gluten which is formed by the process of kneading remains as a sticky mass. When this moist mass is kneaded and rolled until all the moisture is taken out of it that can be removed in this way, it may be weighed and the proportion of moist gluten in the sample determined. It may then be placed in an oven and dried, and then the proportion of dry gluten secured. The following method is one which is easily applied. Place 10 grams of the sample in a porcelain dish and moisten with from 6 to 7 cubic centimeters of water, knead, and allow to stand for an hour. Work into a ball, being careful that none of the material adheres to the dish. Holding the mass in the hand knead it in a slow stream of cold water until the starch and all soluble matter are washed out. Place the ball of gluten thus formed in cold water and allow to stand for one hour; remove from water, press as dry as possible between the hands, roll into a ball, and weigh in a flat-bottomed dish. After weighing, place the ball of moist gluten in the drying oven for twenty hours; cool and weigh.

Gluten Tester.

—A simple test for determining the approximate percentage of gluten in flour may be used, based upon the principle that the viscosity of dough is a measure of its practical gluten content. The name applied to a gluten tester is farinometer.

A convenient form of farinometer devised by Kedzie is shown in the accompanying figure. It is patterned somewhat upon the plan of Jago’s viscometer. The instrument is shown in parts in Fig. 34. The instrument as in use is exhibited in Fig. 35. Parts shown in Fig. 34 are as follows: No. 1 is the stand or support of the parts. No. 2 is the cap of No. 1, and discloses the half-inch opening (half closed by the slide) through which the dough is forced by the pressure of the rod No. 4. The slide by which this opening is closed is plainly shown; also the socket for holding No. 3. No. 3 is a brass tube 3 inches high and 1 inch internal diameter, with a small knob to fit into the notched opening in the side of the socket seen in No. 2, to hold No. 3 firmly in place. No. 4 is a steel rod ¹⁵⁄₁₆ inch in diameter and 12 inches long, with a thin brass cap 1 inch in diameter, beveled slightly so that the front edge fills the barrel of No. 3 without friction, and is yet dough-tight. Near the top the rod is marked into inch spaces.

In using the farinometer two points are considered:

1. The water-absorbing power of a flour, or the percentage of water it will take up to form a dough of a certain consistency.

2. The viscosity of such dough, or its resistance to change of form under a uniform force; e. g., the length of time in seconds required to force a cylinder of dough 1 inch high through a hole one-half inch in diameter under the pressure of a vertical steel rod 13 inches long and weighing 2¹⁄₂ pounds avoirdupois.

Bleaching of Flour.

—At the present time flour is extensively bleached for the purpose of making an inferior article resemble a superior one. By this means a greater percentage of the flour produced can be rated as of first quality. Ozone and oxids of nitrogen developed by electrical discharges are the principal bleaching agents employed. Bleached flour should bear a label indicating to the purchaser the character of the manipulation to which it has been subjected.

Adulterations of Flour.

—The adulteration of wheat flour is not practiced to any extent in this country. The most common adulteration arises from grinding with wheat foreign seeds and other foreign matter, rust, smut, etc., which may be present in the grain. Other adulterations are the mixture with wheat flour of the starch or flour of maize and other cereals. The adulteration with any form of terra alba or white powdered earthy substance is exceedingly rare. Although some attempts have been made to introduce such adulterations in this country they have not reached any commercial success. The adulterations, with the exception of those with white earthy powders, are most readily ascertained by microscopic examination for foreign matters and other varieties of starch than grow naturally in the wheat.

Standard.

—The United States standard for flour is as follows:

Flour is the fine, sound product made by bolting wheat meal and contains not more than thirteen and one-half (13.5) percent of moisture, not less than one and twenty-five hundredths (1.25) percent of nitrogen, not more than one (1.0) percent of ash, and not more than fifty hundredths (0.50) percent of fiber.

Graham flour is unbolted wheat meal.

Whole wheat flour, entire wheat flour, improperly so called, is fine wheat meal from which a part of the bran has been removed.

Gluten flour is the product made from flour by the removal of starch, and contains not less than five and six-tenths (5.6) percent of nitrogen and not more than ten (10) percent of moisture.

Age of Flour.

—The freshly ground flour is most highly esteemed by many consumers on account of palatability and freedom from all danger of mold and ferments. Older flours are likely to lose flavor, become moldy and infested with weavil and other insect pests. The last-named evils are avoided by the use of wheat containing no fungus, none of the eggs of the weavil, nor of other insects, and enclosing the freshly ground flour in packages not accessible to infection. Even then it is advisable to consume the flour as soon as convenient after the milling process. Many manufacturers and experts contend that flour is improved by keeping for a certain length of time, and this contention is based on the assumption that the flour assumes a lighter color and improves in flavor on keeping. There is of course a certain limit to improvements of this kind.

Substitutes for Flour.

—Wholesome ingredients are used in part instead of flour in bread making, and when that fact is clearly made known the admixture of these substances with flour is not considered an adulteration. Bread which is made of an admixture of Indian corn meal with flour or rye flour with flour or other cereal products is well liked by many people. Potatoes are also used very often in bread making. Acorns, buckwheat, and other farinacious and oily substances are also employed. The admixture of inert substances with flour merely to increase the bulk and weight of the loaf, even if notified, cannot be regarded as other than an adulteration.

In times of famine such admixtures are sometimes made in order to increase the size and weight of the loaf. Such substances are known in times of famine as “hunger bread.” Finely ground straw, bark, the hulls of nuts, etc., are often used for this purpose. These bodies practically have no nutritive value and serve no useful purpose except to deceive the eater respecting the quantity of bread he consumes.

BREAD.

The term “Bread” when used alone is understood in this country to apply to bread made from wheat flour or some form of wheat. If made from other cereals a prefix is used to distinguish this fact, as Indian corn bread, rye bread, etc. The term bread includes also the materials which are used necessarily therewith in the ordinary process of baking. Thus, the term bread would apply to a loaf which contains not only the wheat flour as the base and chief part of its mass but also the yeast or other leavening agent employed, together with salt, lard, or butter used in its preparation. The presence of these bodies, used in the sense above described, is not regarded as an adulteration. The term “bread,” however, is not to be used to include those other forms of nutriment made from wheat flour in which condimental substances, especially sugar, are used to such an extent as to give the dominant taste of the condiment or condiments employed. Thus, the ordinary cake of all descriptions, tarts, puddings, and other edible substances made largely from wheat flour, but to which the condiment or condiments impart a distinct taste, are not included under the term bread.

In the generic sense the term bread may be used in the largest signification to signify food in general.

Varieties of Bread.

—In general all forms of bread may be divided into two great classes, leavened and unleavened. By far, the greater quantity of bread consumed belongs to the former class. Unleavened bread is used chiefly for certain religious festivals, in the form of biscuits or in certain varieties of Indian corn bread such as hoe cake, johnnie cake, etc. Of the leavened bread there are two distinct classes, namely, bread which is baked and eaten cold and bread which is consumed hot from the oven. Bread intended to be consumed cold is generally eaten within twenty-four or forty-eight hours from the time of making though some varieties may be kept for an indefinite period. The use of hot bread is not commended by hygienists though it is difficult to see why, when properly made, the consumption of a good hot roll can be regarded as injurious. The apparent injury which may result therefrom is probably due to the larger quantity eaten on account of greater palatability than is the case with cold bread. That variety of bread which is baked so as to present a maximum of crust and made of flour which gives a tough consistency to the loaf is most highly regarded both for palatability and nutritive purposes. This form of bread is improperly called French or Vienna rolls in this country.

Unleavened bread is particularly advisable for use in emergency rations for marching soldiers, in logging camps, etc. This bread is compact, comparatively free of moisture and has a high nutritive value. The leavened bread may be divided into distinct classes in respect of the leavening agent employed.

Class 1 is bread in which the leavening agent is yeast. Class 2 is bread in which the natural ferments residing in the flour or wheat are utilized for the leavening agent as in the making of that variety known as salt rising bread. Class 3 includes that form of bread in which the leavening is secured by chemical reagents mixed with the dough. Class 4 includes that variety in which a leavening reagent such as carbon dioxid or air is mechanically incorporated with the dough during the kneading process.

Unleavened bread is also divided into several technical forms. The first class includes the biscuit of commerce, sometimes incorrectly called crackers, and intended to be used soon after preparation. The second class includes biscuits which are intended for long storage and transportation. The third class includes wafers and other delicate forms of unleavened bread for special use. Class 4 is the unleavened loaves which are made most frequently from Indian corn meal and intended to be eaten while still hot. Class 5 includes any miscellaneous unleavened loaves or cakes made in various ways and for different purposes.

In nearly all forms of unleavened bread made from wheat flour the dough is thoroughly beaten, and mechanically mixed or kneaded, in order to make it lighter in color and more crisp and hard after baking.

Yeast.

—Bakers’ yeast is one form of the ordinary yeast ferments or a mixture thereof producing alcoholic fermentation under proper conditions. All flour contains a certain quantity of sugar which is easily fermented. By the action of the yeast upon this sugar carbon dioxid and alcohol are formed. The particles of carbon dioxid become entangled in the gluten of the wheat flour when it is mixed into a dough and thus make the mass spongy and light. When placed in the oven to be baked these minute particles of carbon dioxid expand still more and produce additional lightness and sponginess of the loaf. The yeast may be propagated from one mass of dough to another, may be used in a moist state or, as is very commonly the case, manufactured in large quantities, and sold either moist or more commonly in a partially dried and pressed cake.

Spontaneous Ferments.

—All cereals contain ferments of a character to produce alcoholic fermentation spontaneously under proper conditions. It is possible even to ferment dough by seed from one loaf to another or by developing a spontaneous fermentation. This method is quite a common one in the rural districts, and all bread made in this way is known as salt rising bread. It may be made according to the following receipt:

A quarter of a pint of fresh whole milk is slowly heated to near the boiling point, but not allowed to boil. This process will sterilize the milk and prevent the development of a too rapid lactic fermentation in the subsequent processes. The heated milk is added to a quantity of maize meal sufficient to make with the milk a stiff batter, and the whole is thoroughly mixed. The vessel containing the batter is wrapped with paper and then with a heavy flannel cloth, and kept in a warm place at a uniform temperature of about blood heat for several hours, until fermentation is fully established and the batter assumes a definite sour odor. At this point a teaspoonful of salt is stirred into a pint of blood-warm water and into this a sufficient quantity of high-grade wheat flour is stirred to make a moderately stiff batter. This is thoroughly mixed with the sour mass obtained by the previous fermentation and the mixture exposed for from three-fourths to one hour to a blood heat as before. If the fermentation has been well conducted the mass will now be in a sufficiently active state to secure a proper porosity of the loaf. The salt rising thus prepared is mixed with a wheat flour dough made with warm water in sufficient quantities to make from four to six loaves, the whole mass well kneaded, molded into loaves and put aside at a temperature of blood heat until the fermentation has proceeded far enough to make the loaf light and spongy. The loaf is then baked in the ordinary way.

Chemical Aerating Agents.

—In this country a very common method of aerating bread is practiced, based upon the use of certain chemical reagents which when mixed in the dough set free carbon dioxid. These reagents are known as baking or yeast powders and are especially prized by reason of the fact that it is possible with their aid to prepare in a few moments a light spongy loaf or roll which would require from 10 to 24 hours to make by the ordinary fermenting with yeast. The principal objection to the use of baking powder lies in the fact that the residues arising from the chemical reaction are necessarily left in the loaf. While these residues may not have any specific or poisonous properties they increase the quantity of mineral matter in the bread, and this mineral matter is in the inorganic state and as such does not take any part in the process of nutrition. It can only be regarded as a waste product, burdening, to that extent, the excretory organs of the body.

Constituents of Baking Powder.

—The essential constituents of baking powder are a carbonate of some kind and an acid reagent capable of decomposing this carbonate and setting the carbon dioxid free. The common carbonate of a baking powder is bicarbonate of soda. The classification of baking powders rests upon the acid elements which they contain. They may be classified as follows: (1) Cream of tartar baking powder, in which the acid constituent is cream of tartar which is known chemically as acid potassium tartrate. Other forms of tartaric acid may be used in baking powders of this class but they are not common. (2) Phosphate powders, in which the acid constituent is phosphoric acid usually in the form of the acid phosphate of lime. (3) Alum powders in which the acid constituent is alum or some form of aluminium sulfate, usually the basic sulfate of alumina.

The acid and basic constituents of these powders may be kept in separate containers and mixed together at the time of making the dough. A more common form is to use them in such a way that until they mix with the dough they do not exert any notable effect upon each other. For instance, perfectly dry bicarbonate of soda and perfectly dry acid potassium tartrate may be mixed together and kept for quite a while without any notable decomposition of the bicarbonate taking place.

In order to render any such possible action minimum in its effect it is customary to add to the mixture a small quantity of starch, milk sugar, or some other diluent. These materials tend to keep apart the particles of acid and base and render it possible to make a mixture of them which may be kept for a long while without any notable loss of leavening power. When a cream of tartar baking powder is mixed with dough the moisture of the dough gradually dissolves the two ingredients and in this state a chemical reaction occurs between them. The carbon dioxid is set free as a gas, commonly known as carbonic acid. The mineral substance which results is a tartrate of sodium and potassium that is a union of tartaric acid with potash and soda. This compound is commonly known under the term of Rochelle salts. If there be a sufficient quantity of water in the bread to allow the Rochelle salts to crystallize in the usual way a portion of the water becomes incorporated with the salt. Two teaspoonsful of a tartrate baking powder leave a residue of about 11 grams (165 grains) of crystallized Rochelle salts in the loaf.

Phosphate Powders.

—As has already been said, the acid constituent of phosphate powder is chiefly acid phosphate of lime. In this case the acid phosphate of lime decomposes the bicarbonate of soda with the production of carbon dioxid and leaves a residue consisting of a mixture of sodium and lime phosphate. If in two teaspoonsful of phosphate powder there are approximately 16 grams (250 grains) there is formed a crystallized residue, about an equal weight of phosphate of soda and lime, which is left in the loaf.

Alum Powders.

—Perhaps by far the largest part of baking powders used contain alum in some form as the acid constituent. Formerly the common substance known as alum or burnt alum was employed but in late years an aluminium basic salt known as basic sulfate of aluminium has largely succeeded the old form of alum. When the reaction takes place in the dough between these two constituents of alum baking powder there is formed an equivalent quantity of sulfate of soda and hydroxid of alumina if the acid constituent be basic aluminium sulfate.

The quantity of residue left in the loaf if two teaspoonsful of baking powder be used is about 11 grams (165 grains).

Harmfulness of Baking Powder Residues.

—The question of the harmfulness of the residues left by the various forms of baking powder is one which has been of much interest to the hygienist and physician. It is not claimed in any case that these residues are beneficial. The principal question which has been discussed is which of them is the least harmful. This is a question which it is not proper to enter into in this manual. It might, however, not be out of place to say that the use of chemical reagents for leavening bread is not as advisable as the use of the ordinary fermentation. It would be better, evidently, if all people used more yeast bread and less baking powder rolls. At the same time the utility and convenience of baking powder cannot be denied, and this is a factor which must be taken into consideration in the general discussion and final resolution of the question.

Character of Alum Residues.

—Every one is agreed that the substance known as alum, namely, the sulfate of alumina in conjunction with another mineral or base, such as soda, potash, or ammonia, is not a desirable constituent of food products. In the manufacture of baking powders containing alum an effort is made to so balance the constituents that when the reaction is completed no undecomposed alum remains. If this condition is secured in every instance the materials which remain in the bread are not alum but the residues above mentioned, consisting of aluminium hydrate, and sulfates of soda, potash, or ammonia.

The residue of chief importance is the hydroxid or hydrate of alumina, which is the form in which the alumina itself should appear when a complete reaction like that defined above takes place. When the hydroxid of alumina is dried and especially when ignited it is converted into an oxid of alumina which is highly insoluble in water and only slightly soluble in a very dilute acid solution. The claim is made by the manufacturer of alum powders that the aluminium residue which is formed is insoluble in the digestive juices and therefore cannot produce any effect usually ascribed to the soluble salts of aluminium. It is important that the conditions which are found in the baking of a loaf are such as to produce this highly desirable result. The temperature of the interior of the loaf during baking does not rise much above that of boiling water, although the exterior temperature, which is sufficient to produce the browning of the crust, is very much above that temperature. It is evident that as long as any considerable proportion of water remains in the loaf it will be difficult to raise the interior of the loaf to the temperature just mentioned, and if this were done the caramelization would take place throughout the whole loaf. Unfortunately, from a scientific point of view the investigation of this subject has not been always undertaken under conditions which are wholly beyond criticism. Many of the investigations have been in the interest of rival baking powder companies, and it is very desirable that this matter should be undertaken in a wholly unbiased way and conducted in such a manner as to lead to results which all will accept. Chemical and physiological investigations, which have even as a remote object the promotion of the sale of one compound and the repression of the sale of another, lose at the outset much of that claim upon the public confidence which such investigations made from a purely scientific point of view should have.

General Statement.

—In respect of the use of chemical leavening agents in general it may be said that they introduce an extraneous product into the bread which is not likely to promote the health and which, therefore, on general principles should be excluded. On the other hand, large experience has shown that the consumption of bread made by these leavening agents does not produce any general effect upon the public health which is noticeable. This, it is understood, is not any valid argument in favor of the process. It must also be acknowledged that a fermentation of a bread with yeast also introduces extraneous matter into the food, viz., alcohol and congeneric products of fermentation, and hence this process may be open to a certain extent to the same objection as the one above. It is too early yet to formulate definite principles either of inclusion or exclusion of these products, and the purpose of this manual is secured when the general character and effects thereof are briefly outlined.

Composition of Bread.

—Because of the many different methods of bread making which are practised it is not possible to give in a chemical form an analysis which would do more than represent in general the character of the bread in common use. For instance, the quantity of water which is found in bread varies greatly and the nature of bread itself must be influenced by the character of the flour from which it is made. The flour depends upon the quality of the wheat used in its manufacture. Hence the same brand of bread prepared in the same way and baked in the same manner must necessarily vary in composition from season to season and even from day to day. It must be understood also that it is a very common custom in the United States to use milk in the mixing of dough, and thus a food product is introduced which of itself is not of constant character. Some bakers use whole milk, others skimmed, and others sour milk.

A very good formula for mixing dough for bread making consists in using the following proportions of ingredients mentioned:

When properly leavened and kneaded and baked these quantities of materials will make a loaf of bread weighing 2750 grams.

Average Composition of Bread.

—In the following tables are given the average composition of bread of different classes. Class 1 is composed of loaves of the so-called Vienna or French type; Class 2 consists of what is known as home made bread or bread baked at the home and not in the bakery; Class 3 consists of bread made from graham flour; Class 4 consists of bread made largely of rye flour; Class 5 is a second collection of home made bread which may be very properly compared with Class 2; Class 6 consists of bread of miscellaneous origin bought on the open market. The data given represent the mean composition of numbers of samples (Bull. 13, Bureau of Chemistry):

A Typical American High-grade Yeast Bread.

—In conjunction with the actual analyses given above it is of interest to combine as many analytical data as can be conveniently secured for the purpose of determining what the average composition of a high-grade typical yeast bread is. This comparison leads to the following composition:

Of the ash mentioned in the above analysis .50 percent may be ascribed to the natural mineral ingredient of flour and 1 percent to added salt.

The chief variations from the typical composition of bread made from high-grade flour are found in the moisture and ether extract. The moisture may rise above 40 percent in breads made of flour rich in gluten or sink to 30 percent or under when flour of an inferior gluten content is employed. The quantity of ether extract depends chiefly upon the amount of milk which is used in the making of bread and the amount of fat employed either in the bread itself or in greasing the pan in which it is baked. There is great difficulty in extracting a fatty body which has been mixed with a glutinous material like flour. The analytical data, therefore, do not represent in the ether extract all the fat naturally present in the flour plus that added in the making of dough or in baking.

The quantity of moisture in bread may also be determined largely by the time of baking and the temperature of the oven. A bread baked for a long while at a low temperature will be much drier than a bread baked quickly at a high temperature. The high temperature solidifies the exterior of the loaf so as to make it difficult for the interior moisture to escape. By quickly baking the bread the temperature of the interior does not reach so high a temperature as in an oven with a low temperature and a long-continued heat.

Standard for Moisture.

—The quantity of moisture in bread of standard quality in the District of Columbia may not exceed 31 percent.

The average temperature of the baking oven is about 240° C. (464° F.).

Quantity of Sugar in Bread.

—The quantity of sugar found in fermented bread is always less than that present in the flour, added in milk, or otherwise introduced in the preparation of the dough. The sugar disappears largely under the influence of the fermentation due to the yeast.

Quantity of Ash.

—The quantity of ash in bread is uniformly higher than the content of mineral matter in the flour. This is due to the addition of common salt which is uniformly employed in all bread, and in the case of bread made from baking powder the retention of the mineral residues in the loaf increases to that extent the content of ash. With the exception of the ash, the ether extract or fat, the sugar, and the dry material of bread correspond in quantity to the same materials in the flour from which it is made, except the loss due to the caramelization of the crust.

Acidity of Bread.

—The development of the lactic acid ferments is important in regard to hygienic conditions and to palatability. Flour contains practically no acid in a free state, and the acidity of bread is itself due to the changes which take place in its preparation under the influence of the ferments therein. Bread baked in the usual manner after the yeast ferments have exerted their activity shows the presence of acetic acid, lactic acid, and other acids and salts. The acidity of bread adds to its palatability and also, doubtless, to its digestibility. Bread, containing, as it does, a large percentage of protein, is digested in an acid medium. The natural acidity of bread, therefore, must be regarded as beneficial.

Comparative Nutritive Properties of Indian Corn Bread and Wheat Bread.

—There is a widespread opinion that the products of Indian corn are less digestible and less nutritious than those of wheat. This opinion amounts to a conviction in most European countries, where the products obtained by the milling of Indian corn are not regarded as fit for human food in an unmixed state. The above opinion, it appears, has no justification either from the chemical composition of the two bodies or from recorded digestive and nutritive experiments.

A study of the analytical data of the whole grain shows that in so far as actual nutrition is concerned the maize is fully as nutritious as wheat. In respect of its content of fat Indian corn and its direct products easily take precedence of all the other cereals, with the exception of hulled oats. In round numbers Indian corn flour or bread made therefrom contains twice as much fat or oil as wheat, three times as much as rye, twice as much as barley, and nearly as much as hulled oats. In regard to digestible carbohydrates, that is digestible starch, sugar, dextrin, and fiber, Indian corn flour possesses a higher content than hulled oats and almost the same content as wheat. In regard to digestible protein Indian corn has nearly the same quantity as the other leading cereals, except oats. What it lacks, however, in its quantity of protein in so far as nutrition is concerned is more than made up in its excess of fat.

Comparative Digestibility and Nutrition of Wheat and Indian Corn from Experiments Made in South Dakota Station, Bulletin 38.

—Pigs were fed with Indian corn and wheat, or rather the ground Indian corn and ground wheat, and it was found that pound for pound there was a greater gain in the case of Indian corn flour than wheat. For 100 pounds of flour fed the average gain with Indian corn was 21.83 pounds and where wheat flour was used 20.79 pounds. These experimental data show that in regard to nutritive properties Indian corn flour cannot be considered inferior to wheat flour. Indian corn bread is particularly well suited for persons engaged in hard manual labor. A ration which is composed largely of Indian corn products and oatmeal is found to be particularly valuable for those engaged in lumbering, harvesting sugar-cane, etc.

Indian Corn Flour Pudding.

—Various forms of pudding are prepared from Indian corn flour. Among the most important is that known in the New England States as hasty pudding and in the west and south as mush. A simple method of preparing Indian corn pudding, hasty pudding, or mush is to stir into water, very slowly, the Indian corn flour in such a way as to avoid the formation of lumps. The flour should be sifted into the water either cold or at boiling temperature and the mixture vigorously stirred meanwhile. By this means a thin, uniform paste is secured which is allowed to cook slowly until quite thick in consistence and until all the starch granules are thoroughly disintegrated. The product is improved by allowing to stand for several hours at near the boiling point after the cooking is finished, provided precautions are taken not to allow the mass to become too solid. This product is eaten hot with butter, milk, or cream, or is much prized when allowed to cool, cut into thin slices and fried. A very important dish for the children of working people and farmers of the south and west is mush and milk, namely the product above mentioned eaten with skim milk. This mixture forms a palatable and wholesome diet. Various other forms of pudding are made into which Indian corn enters to a greater or less degree.

Composition of Biscuits.