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:
| Flour, | 2,000 | grams |
| Whole milk, | 500 | „ |
| Water, | 650 | „ |
| Salt, | 25 | „ |
| Yeast cake, | 10 | „ |
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):
| Moisture. | Protein. | Ether Extract. | Fiber. | Ash. | Starch and Sugar. | Salt. | Calories. | |
|---|---|---|---|---|---|---|---|---|
| Class 1. | Perct. | Perct. | Perct. | Perct. | Perct. | Perct. | Perct. | |
| 38.71 | 8.09 | 1.06 | .62 | 1.19 | 53.72 | .57 | .. | |
| In the dry substance, | .. | 13.23 | 1.73 | .97 | 1.95 | 83.10 | .93 | 4458 |
| Class 2. | ||||||||
| 33.02 | 7.24 | 1.95 | .24 | 1.05 | 56.75 | .56 | .. | |
| In the dry substance, | .. | 10.80 | 2.91 | .36 | 1.55 | 84.75 | .84 | 4497 |
| Class 3. | ||||||||
| 34.80 | 8.15 | 2.03 | 1.13 | 1.59 | 53.40 | .69 | .. | |
| In the dry substance, | .. | 12.51 | 3.13 | 1.74 | 2.29 | 82.06 | 1.07 | 4434 |
| Class 4. | ||||||||
| 33.42 | 7.88 | .66 | .62 | 1.84 | 56.21 | 1.00 | .. | |
| In the dry substance, | .. | 11.86 | 1.02 | .95 | 2.79 | 84.36 | 1.50 | 4395 |
| Class 5. | ||||||||
| 36.16 | 7.10 | 1.14 | .26 | 1.06 | 54.53 | .58 | .. | |
| In the dry substance, | .. | 11.17 | 1.75 | .41 | 1.68 | 85.41 | .92 | 4395 |
| Class 6. | ||||||||
| 34.41 | 6.93 | 1.48 | .30 | 1.00 | 56.18 | .49 | .. | |
| In the dry substance, | .. | 10.59 | 2.21 | .46 | 1.53 | 85.66 | .76 | 4401 |
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:
| Moisture, | 35.00 | percent |
| Protein, | 8.00 | „ |
| Ether extract, | .75 | „ |
| Starch and sugar, | 54.45 | „ |
| Fiber, | .30 | „ |
| Ash, | 1.50 | „ |
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.
—The composition of a biscuit or dry unleavened bread does not differ essentially from that of the ordinary bread except in the content of moisture. The biscuits are usually baked in thin cakes or loaves which become heated throughout and sometimes caramelize throughout a large part of their substance. This favors the expulsion of the greater part of the moisture which the dough originally contained. The average composition of biscuits is shown in the following data:
| Moisture, | 7.13 | percent |
| Protein, | 9.43 | „ |
| Ether extract, | 8.67 | „ |
| Fiber, | .47 | „ |
| Ash, | 1.57 | „ |
| Salt, | .99 | „ |
| Starch and sugar, | 73.77 | „ |
In the dry substance:
| Protein, | 10.18 | percent |
| Ether extract, | 9.33 | „ |
| Fiber, | .53 | „ |
| Ash, | 1.70 | „ |
| Salt, | 1.08 | „ |
| Starch and sugar, | 78.79 | „ |
| Calories, | 4,755 |
The above data show that biscuits vary in composition from bread chiefly in their content of moisture and fat or oil. The moisture, as is noted, is very low, while the quantity of fat which the biscuit contains is from 8 to 10 times as great as that contained in flour from which they are made. The salt content and the mineral ingredients of the biscuit are often higher than in bread or flour. Inasmuch as a large quantity of fat and salt are used commonly in the manufacture of biscuits the presence of these bodies cannot in any sense be regarded as an adulteration. In forty-eight samples examined only four were free of notable quantities of added fat. In one case over 16 percent of fat was found, and as it has been shown that all the fat which is added is not extracted by ether it is evident that in this case an amount of fat equal to 20 percent of the weight of the flour may have been used.
It appears, from a study of the composition of biscuits, that it is advisable to use them as a relish or delicacy for eating with cheese, etc., in ordinary daily life, while they become almost a necessity in some form or other in the preparation of emergency rations for marching armies, on shipboard, in logging camps, etc. It is not advisable to employ them in the daily diet to the exclusion of bread. Their nutrient contents have, in comparison with bread, a lower coefficient of digestibility, due largely to the added fat.
Amount of Sugar Lost in Fermentation.
—The total quantity of sugar and other carbohydrates lost in fermentation amounts to about 2 percent of the weight of flour used. Sometimes it is much greater and sometimes less than this. The nutritive value of the product is diminished in proportion to the extent of the loss of sugar. The carbon dioxid produced during fermentation has no food value, and the alcohol is largely lost in the form of vapor during the process of baking. About half the loss is due to carbon dioxid and half to alcohol. The alcohol, although lost mostly during the baking, serves a useful purpose,—in the expansion of the vapor it aids the carbon dioxid in making the bread more porous. The hydrolysis which takes place in baking converts some of the starch to dextrinoid or saccharoid conditions. It is evident that from 6 to 8 percent of total starch present in the flour is changed during the fermentation and baking into more or less soluble forms.
Fig. 36.—Comparative Appearance of Breads of Different Kinds.
Texture and Size of Loaves Made from Different Kinds Of Flour.
—The variations in bread and size of loaves made from different kinds of flour when the conditions of fermentation and baking are the same depends upon the texture and quantity of the gluten material in the flour. The difference in the appearance and size of loaves is shown by a photograph of the cross-sections of three loaves of bread in [Fig. 36].
It is seen that the loaves made from graham flour and entire wheat flour are somewhat coarser in structure and are less in size than those made from the same quantity of standard patent flour.