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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.
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 fortyeight 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
CHEMICAL AERATING AGENTS.
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 constitutents 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
CHARACTER OF ALUM RESIDUES.
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.