Part 10 (1/2)
DELETERIOUS ADULTERATIONS OF FLOUR.--Besides the fraud frequently practiced of compounding whole-wheat flour from inferior mill products, white flour is sometimes adulterated--more commonly, however, in European countries that in this--with such substances as alum, ground rice, plaster of Paris, and whiting. Alum is doubtless the most commonly used of all these substances, for the reason that it gives the bread a whiter color and causes the flour to absorb and retain a larger amount of water than it would otherwise hold. This enables the user to make, from an inferior brand of flour, bread which resembles that made from a better quality. Such adulteration is exceedingly injurious, as are other mineral substances used for a similar purpose.
The presence of alum in flour or bread may be detected in the following way: Macerate a half slice of bread in three or four tablespoonfuls of water; strain off the water, and add to it twenty drops of a strong solution of logwood, made either from the fresh chips or the extract.
Then add a large teaspoonful of a strong solution of carbonate of ammonium. If alum is present, the mixture will change from pink to lavender blue.
The _Journal of Trade_ gives the following simple mode of testing for this adulterant: ”Persons can test the bread they buy for themselves, by taking a piece of it and soaking it in water. Take this water and mix it with an equal part of fresh milk, and if the bread contains alum, the mixture will coagulate. If a better test is required, boil the mixture, and it will form perfect clot.”
Whiting can be detected by dipping the ends of the thumb and forefinger in sweet oil and rubbing the flour between them. If whiting is present, the flour will become sticky like putty, and remain white; whereas pure flour, when so rubbed, becomes darker in color, but not sticky. Plaster of Paris, chalk, and other alkaline adulterants may be detected by a few drops of lemon juice: if either be present, effervescence will take place.
CHEMISTRY OF BREAD-MAKING.--Good flour alone will not insure good bread. As much depends upon its preparation as upon the selection of material; for the very best of flour may be transformed into the poorest of bread through improper or careless preparation. Good bread cannot be produced at random. It is not the fruit of any luck or chance, but the practical result of certain fixed laws and principles to which all may conform.
The first step in the conversion of flour into bread is to incorporate with it a given amount of fluid, by which each atom of flour is surrounded with a thin film of moisture, in order to hydrate the starch, to dissolve the sugar and alb.u.men, and to develop the adhesiveness of the gluten, thus binding the whole into one coherent ma.s.s termed _dough_, a word from a verb meaning to wet or moisten. If nothing more be done, and this simple form of dough be baked, the starch granules will be ruptured by the heat and thus properly prepared for food; but the moistening will have developed the glue-like property of the gluten to the extent of firmly cementing the particles of flour together, so that the ma.s.s will be hard and tough, and almost incapable of mastication. If, however, the dough be thoroughly kneaded, rolled very thin, made into small cakes, and then quickly baked with sufficient heat, the result will be a brittle kind of bread termed unleavened bread, which, although it requires a lengthy process of mastication, is more wholesome and digestible than soft bread, which is likely to be swallowed insufficiently insalivated.
The gluten of wheat flour, beside being adhesive, is likewise remarkably elastic. This is the reason why wheat flour is much more easily made into light bread than the product of other cereals which contain less or a different quality of gluten. Now if while the atoms of flour are supplied with moisture, they are likewise supplied with some form of gaseous substance, the elastic walls of the gluten cells will become distended, causing the dough to ”rise,” or grow in bulk, and at the same time become light, or porous, in texture.
This making of bread light is usually accomplished by the introduction of air into the dough, or by carbonic acid gas generated within the ma.s.s, either before or during the baking, by a fermentative or chemical process.
When air is the agency used, the gluten, by its glue-like properties, catches and retains the air for a short period; and if heat is applied before the air, which is lighter than the dough, rises and escapes, it will expand, and in expanding distend the elastic glutinous ma.s.s, causing it to puff up or rise. If the heat is sufficient to harden the gluten quickly, so that the air cells throughout the whole ma.s.s become firmly fixed before the air escapes, the result will be a light, porous bread. If the heat is not sufficient, the air does not properly expand; or if before a sufficient crust is formed to retain the air and form a framework of support for the dough, the heat is lessened or withdrawn, the air will escape, or contract to its former volume, allowing the distended glutinous cell walls to collapse; in either case the bread will be heavy.
If carbonic acid gas, generated within the dough by means of fermentation or by the use of chemical substances, be the means used to lighten the ma.s.s, the gluten by virtue of its tenacity holds the bubbles of gas as they are generated, and prevents the large and small ones from uniting, or from rising to the surface, as they seek to do, being lighter than the dough. Being thus caught where they are generated, and the proper conditions supplied to expand them, they swell or raise the dough, which is then termed a loaf. (This word ”loaf” is from the Anglo-Saxon _hlifian_, to raise or lift up.) The structure is rendered permanent by the application of heat in baking.
BREAD MADE LIGHT BY FERMENTATION.
For general use, the most convenient form of bread is usually considered to be that made from wheat flour, raised or made light by some method of fermentation, although in point of nutritive value and healthfulness, it does not equal light, unfermented, or aerated bread made without the aid of chemicals.
THE PROCESS OF FERMENTATION.--Fermentation is a process of decomposition, and hence more or less destructive to the substances subjected to its influence. When animal and vegetable substances containing large amounts of nitrogenous elements are in a moist state and exposed to air, they very soon undergo a change, the result of which is decomposition or decay. This is occasioned by the action of germs, which feed upon nitrogenous substances, as do the various species of fungi. Meat, eggs, milk, and other foods rich in nitrogenous elements can be preserved but a short time if exposed to the atmosphere. The carbonaceous elements are different in this respect. When pure starch, sugar, or fat is exposed to the air in a moistened state, they exhibit the very little tendency to change or decay. Yet if placed in contact with decomposing substances containing nitrogen, they soon begin to change, and are themselves decomposed and destroyed. This communication of the condition of change from one cla.s.s of substances to another, is termed fermentation. If a fermenting substance be added to a watery solution containing sugar, the sugar will be changed or decomposed, and two new substances, alcohol and carbonic acid gas, are produced.
The different stages of fermentation are noted scientifically as alcoholic, acetous, and putrefactive. The first is the name given to the change which takes place in the saccharine matter of the dough, which results in the formation of alcohol and carbonic acid gas. This same change takes place in the saccharine matter of fruits under the proper with conditions of warmth, air, and moisture, and is utilized in the production of wines and fermented liquors.
In bread-making, the alcohol and carbonic acid gas produced during the fermentation, are formed from sugar,--that originally contained in the flour and the additional quant.i.ty formed from starch during the fermenting process. It is evident, therefore, that bread cannot be fermented without some loss in natural sweetness and nutritive value, and bread made after this method should be managed so as to deteriorate the material as little as possible.
If this fermentation continues long enough, the acetous fermentation is set up, and _acetic_ acid, the essential element of vinegar, is formed and the dough becomes sour. If the process of fermentation is very much prolonged, the putrefactive change is set up, and the gluten is more or less decomposed.
If the dough be baked during the alcoholic and carbonic-acid stage of fermentation, the gas will render the loaf light and porous. The alcohol will be dissipated by the heat during the baking, or evaporated shortly afterward, provided the baking be thorough. If the fermentation is allowed to proceed until the acetous fermentation has begun, the loaf, when baked, will be ”sad” and heavy, since there is no longer any gas to puff it up. If, however, during the first or alcoholic stage of fermentation, new material be added, the same kind of fermentation will continue for a certain period longer.
These facts serve to show that great care and attention are necessary to produce good bread by a fermentative process. If the fermentation has not been allowed to proceed far enough to generate a sufficient amount of gas to permeate the whole ma.s.s, the result will be a heavy loaf; and if allowed to proceed too far, acid fermentation begins, the gas escapes, and we have sour as well as heavy bread. It is not enough, however, to prevent bread from reaching the acetous or sour stage of fermentation. Bread may be over-fermented when there is no appreciable sourness developed. Fermentation may be carried so far as to destroy much of the richness and sweetness of the loaf, and yet be arrested by the baking process just before the acetous stage begins, so that it will be light and porous, but decidedly lacking in flavor and substance.
Over-fermentation also develops in the bread various bitter substances which obscure the natural sweetness of the bread and give to it an unpleasant flavor. Many of these substances are more or less harmful in character, and include many poisons known as ptomaines, a cla.s.s of chemical compounds produced by germs whenever fermentation or decomposition of organic matter takes place. Much skill is required to determine at what point to arrest the fermentation, in order to save the sweetness and richness of the bread.
FERMENTATIVE AGENTS.--Fermentation in vegetable matter is always accompanied by the growth of living organisms. The development of these minute organisms is the exciting cause of fermentation and putrefaction.
The germs or spores of some of these fermenting agents are always present in the air. It is well known to housekeepers that if a batter of flour and water and a little salt be kept in a jar of water at a temperature of from 100 to 110, it will ferment in the course of five or six hours. Scientists a.s.sure us that this fermentation is occasioned by the introduction of the spores of certain species of fungi which are continually floating in the atmosphere, and the proper conditions of warmth and moisture being supplied, they at once begin to grow and multiply. This method of securing fermentation is utilized by housewives in making what is termed salt-rising bread. The raising of dough by this process is lengthy and uncertain, and a far more convenient method is to accelerate the fermentation by the addition of some active ferment. The ancient method of accomplis.h.i.+ng this was by adding to the dough a leaven, a portion of old dough which had been kept until it had begun to ferment; but since the investigations of modern chemistry have made clear the properties of yeast, that has come to be considered the best agent for setting up the process of alcoholic fermentation in bread. The use of leaven is still practiced to somewhat in some European countries.
The bread produced with leaven, although light and spongy in texture, has an unpleasant, sour taste, and is much less wholesome than that produced with fresh yeast.
Yeast is a collection of living organisms or plants belonging to the family of fungi, which, like all other plants, require warmth, moisture, and food, in order to promote growth, and when properly supplied with these, they begin to grow and multiply rapidly. Fermentation will not take place at a temperature below 30, it proceeds slowly at 45, but from 70 to 90 it goes on rapidly. Fermentation may be arrested by the exhaustion of either the fermenting agent or the food supply, or by exposure to heat at the temperature of boiling water. This latter fact enables the housewife to arrest the process of fermentation, when the loaf has become sufficiently light, by baking it in a hot oven. Heat destroys most of the yeast cells; a few, however, remain in the loaf unchanged, and it is for this reason that yeast bread is considered less wholesome for dyspeptics than light unleavened bread. It is apparent, then, that the more thoroughly fermented bread is baked, the more wholesome it will be, from the more complete destruction of the yeast germs which it contains.
YEAST.--Next to good flour, the most important requisite in the manufacture of fermented bread is good yeast. The best of flour used in conjunction with poor yeast will not produce good bread. The most convenient and reliable kind of marketable yeast, when fresh, is the compressed yeast. The dry though they are always ready for use, the quality of the bread they produce is generally inferior to that made with either compressed yeast or good liquid yeast. If this sort of yeast must be depended upon, the cakes known as ”Yeast Foam” are the best of any with which we are acquainted.
Of homemade yeasts there are almost as many varieties as there are cooks. Their comparative value depends mainly upon the length of time they will keep good, or the facility with which they can be prepared.
Essentially the same principles are involved in the making of them all; viz., the introduction of a small quant.i.ty of fresh, lively yeast into a mixture of some form of starch (obtained from flour, potato, or a combination of both) and water, with or without the addition of such other substances as will promote fermentation, or aid in preventing the yeast from souring. Under proper conditions of warmth, the small amount of original yeast begins to supply itself with food at once by converting the starch into dextrine, and then into grape sugar, and multiplies itself with great rapidity, and will continue to do so as long as there is material to supply it with the means of growth. While its growth is rapid, its decay is equally so; and unless some means of preservation be employed, the yeast will die, and the mixture become sour and foul. Ordinarily it can be kept good for several days, and under the best conditions, even three or four weeks. After it has been kept from four to six hours, it should be placed in some receptacle as nearly air-tight as possible and set in the cellar or refrigerator, where it can be kept at a temperature not conducive to fermentation.
Thus the little yeast organisms will remain in a quiescent state, but yet alive and capable of multiplying themselves when again surrounded with favorable conditions.