Science in the Kitchen Part 10

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.

The yeast should be kept in gla.s.s or glazed earthen ware. The vessel containing it should be washed and scalded with scrupulous care before new yeast is put in, since the smallest particle of sour or spoiled yeast will ruin the fresh supply in a very short time. It is generally conceded that yeast will keep longer if the material of which it is made be mixed with liquid of a boiling temperature, or cooked for a few minutes at boiling heat before adding the yeast. The reason for this undoubtedly lies in the fact that the boiling kills foreign germs, and thus prevents early souring or putrefaction. The yeast must not be added, however, until the liquid has cooled to a little more than blood heat, as too great heat will kill the yeast cells.

The starch of the potato is thought to furnish better material for the promotion of yeast growth than that of wheat flour; but whether the potato be first cooked, mashed, and then combined with the other ingredients, or grated raw and then cooked in boiling water, makes little difference so far as results are concerned, though the latter method may have the advantage of taking less time. If potatoes are used for this purpose, they should be perfectly mature. New ones will not answer.

Sugar a.s.sists in promoting the growth of the yeast plant, and a small amount is usually employed in making yeast. Hops serve to prevent the yeast from souring, and an infusion of them is frequently used for this purpose.

While it is essential that the water used should be boiling, it is also necessary that the mixture should cooled to a lukewarm temperature before the introduction of the original yeast, as intense heat will kill the yeast plant. Freezing cold will likewise produced the same result.

While a cool temperature is one of the requisites for keeping yeast fresh, care must be taken, especially in winter, that it does not get chilled.

When yeast is needed for bread, it is always the best plan to take a cup to the cellar or refrigerator for the desired quant.i.ty, and re-cover the jar as quickly as possible. A half hour in a hot kitchen would be quite likely to spoiled it. Always shake or stir the whole well before measuring out the yeast. In making yeast, used earthen bowls for mixing, porcelain-lined or granite-ware utensils for boiling, and silver or wooden spoons for stirring.

BITTER YEAST.--It sometimes happens that an excessive use of hops in the making of yeast gives to it so bitter a flavor as to communicate a disagreeable taste to the bread. To correct this bitterness, mix with the yeast a considerable quant.i.ty of water, and let it stand for some hours, when the thickest portion will have settled at the bottom. The water, which will have extracted much of the bitterness, can then be turned off and thrown away. Yeast also sometimes becomes a bitter from long keeping. Freshly burnt charcoal thrown into the yeast is said to absorb the odors and offensive matter and render the yeast more sweet; however, we do not recommend the use of any yeast so stale as to need sweetening or purifying. Yeast that is new and fresh is always best; old and stale yeast, even though it may still possess the property of raising the dough, will give an unpleasant taste to the bread, and is much less wholesome.

TESTS FOR YEAST.--Liquid yeast, when good, is light in color and looks foamy and effervescent; it has a pungent odor somewhat similar to weak ammonia, and if tasted will have a sharp, biting flavor. Yeast is poor when it looks dull and watery, and has a sour odor. Compressed yeast, if good, breaks off dry and looks white; if poor, it appears moist and stringy.

If there is any question as to the quality of yeast, it is always best to test it before use by adding a little flour to a small quant.i.ty and setting it in a warm place. If it begins to ferment in the course of fifteen or twenty minutes, it is good.

STARTING THE BREAD.--Having secured good yeast, it is necessary in some way to diffuse it through the bread material so that it will set up an active fermentation, which, by the evolution of gas, will render the whole ma.s.s light and porous. As fermentation is more sure, more rapid, and requires less yeast to start it when set in action in a thin mixture than when introduced into stiff dough, the more common method of starting fermented bread is by "setting a sponge;" viz., preparing a batter of flour and liquid, to which potato is sometimes added, and into which the yeast is introduced. Some cooks, in making the batter, use the whole amount of liquid needed for the bread, and as the sponge rises, add flour in small quant.i.ties, beating it back, and allowing it to rise a second, third, or even fourth time, until sufficient flour has been added to knead; others use only half the liquid in preparing the sponge, and when it has well risen, prepare a second one by adding the remainder of the liquid and fresh flour, in which case the fermented batter acts as a double portion of yeast and raises the second sponge very quickly. The requisite amount of flour is then added, the dough kneaded, and the whole allowed to rise a third time in the loaf. Other cooks dispense altogether with the sponge, adding to the liquid at first the requisite amount of flour, kneading it thoroughly and allowing it to rise once in ma.s.s and again after molding into loaves. As to the superiority of one method over another, much depends upon their adaptability to the time and convenience of the user; light bread can be produced by either method. Less yeast but more time will be required when the bread is started with a sponge. The end to be attained by all is a complete and equal diffusion of gas bubbles generated during fermentation throughout the whole ma.s.s of dough.

The preferable method of combining the materials needed for the batter is by first mingling the yeast with the water or milk. If condensed or dry yeast is used, previously dissolve it well in a half cupful or less of lukewarm water. Stir the flour slowly into the liquid mixture and beat it _very thoroughly_ so that the yeast shall be evenly distributed throughout the whole.

PROPORTION OF MATERIALS NEEDED.--The material needed for making: the bread should all be carefully measured out beforehand and the flour well sifted. Many housekeepers fail in producing good bread, because they guess at the quant.i.ty of material to be used, particularly the flour, and with the same quant.i.ty of liquid will one time use much more flour that at another, thus making the results exceedingly variable.

With this same brand of flour, this same quant.i.ty should always be used to produce a given amount of bread. This amount will depend upon the quality of the material used. Good flour will absorb a larger quant.i.ty of liquids than that of an inferior quality, and the amount of liquid a given quant.i.ty of flour will take up determines the quant.i.ty of bread that can be produced from it. This amount is chiefly dependent upon the proportion of gluten contained in the flour. One hundred pounds of good flour will absorb sufficient water to produce one hundred and fifty pounds of bread. One reason why bread retains so much water is that during the baking a portion of starch is converted into gum, which holds water more strongly than starch. Again: the gluten, when wet, is not easily dried, while the dry crust which forms around the bread in baking is merely impervious to water, and, like the skin of a baking potato, prevents the moisture from escaping.

Kinds of flour vary so considerably in respect to their absorbent properties that it is not possible to state the exact proportions of flour and liquid required; approximately, three heaping measures of flour for one scant measure of liquid, including the yeast, will in general be found a good proportion. Bread made from the entire wheat will require from one half to one cupful less flour than that made of white flour. A quart of liquid, including the yeast, is sufficient for three ordinary-sized loaves. One half or two thirds of a cup of homemade yeast, according to its strength, or one half a cake of compressed yeast dissolved in a half cup of lukewarm water, will be sufficient for one quart of liquid. It is a common mistake to use too much yeast. It lessens the time required, but the result is less satisfactory. Bread to be set over night requires less yeast.

Whether water or milk should be used for bread-making, depends upon taste and convenience. Bread retains more nearly the natural flavor of the grain if made with water, and is less apt to sour; at the same time, bread made with milk is more tender than that made with water. Bread made with milk requires from one half to one cupful less of flour.

Potatoes are sometimes used in conjunction with flour for bread-making.

They are by no means necessary when good flour is used, but bread made from inferior flour is improved by their use. Only potatoes that are fully matured should be used for this purpose, and they should be well cooked and smoothly mashed. Neither sugar nor salt is essential for the production of good bread, though most cook books recommend the use of one or both. The proportion of the former should not exceed one even tablespoonful to three pints of flour, and the very smallest amount of salt, never more than a half teaspoonful, and better less. No b.u.t.ter or other free fat is required; the tenderness of texture produced by its use can be secured as well by the use of unskimmed milk and thorough kneading.

UTENSILS.--For bread-making purposes, earthen or china ware is preferable to either tin or wooden utensils: being a poor conductor, it protects the sponge from the cold air much more effectually than tin, and is much more easily kept clean and sweet than wood. The utensil should be kept exclusively for the purpose of bread-making, and should never be allowed to contain any sour substance. The bowl should be thoroughly scalded before and after each using. Use silver or granite-ware spoons for stirring the bread. Iron and tin discolor the sponge. For measuring the material, particularly the liquid and the yeast, half-pint cups, divided by marks into thirds and fourths, as shown in the cut, are especially serviceable.

[Ill.u.s.tration: Measuring Cup] [Ill.u.s.tration: Measuring Cup]

WHEN TO SET THE SPONGE.--The time to set the sponge for bread-making is a point each housekeeper must determine for herself. The fact before stated, that temperature controls the activity of fermentation, and that it is r.e.t.a.r.ded or accelerated according to the conditions of warmth, enables the housewife, by keeping the bread-mixture at a temperature of about 50 F., to set her bread in the evening, if desired, and find it light and ready for further attention in the morning. In winter, the sponge will need to be prepared early in the evening and kept during the night at as even a temperature as possible. A good way to accomplish this is to cover the bowl with a clean napkin and afterwards wrap it about very closely with several folds of a woolen blanket. In extremely cold weather bottles of hot water may be placed around the bowl outside the wrappings. In case this plan is employed, care must be taken to have sufficient wrappings between the bread and the bottles to prevent undue heat, and the bottles should be covered with an additional blanket to aid in retaining the heat as long as possible.

If the sponge is set in the evening, if in very warm weather, it should be started as late as practicable, and left in a rather cool place.

Cover closely to exclude the air, but do not wrap in flannel as in winter. It will be likely to need attention early in the morning.

TEMPERATURE FOR BREAD-MAKING.--Except in very warm weather, the ferment or sponge should be started with liquid at a lukewarm temperature.

The liquid should never be so cold as to chill the yeast. Milk, if used, should be first sterilized by scalding, and then cooled before using.

After the sponge is prepared, the greatest care must be taken to keep it at an equable temperature. From 70 to 90 is the best range of temperature, 75 being considered the golden mean throughout the entire fermentative process of bread-making.

After fermentation has well begun, it will continue, but much more slowly if the temperature be gradually lowered to 45 or 50. If it is necessary to hasten the rising, the temperature can be raised to 80 or 85, but it will necessitate careful watching, as it will be liable to over-ferment, and become sour. Cold arrests the process of fermentation, while too great heat carries forward the work too rapidly. Too much stress cannot be laid upon the importance of an equable temperature. The housewife who permits the fermentation to proceed very slowly one hour, forces it rapidly by increased heat the next, and perhaps allows it to subside to a chilling temperature the third, will never be sure of good bread.

Putting the bowl containing the sponge into a dish of warm (not hot) water, or keeping it in the warming oven, or on the back of the range, are all methods which may bring about good results, provided the same degree of heat can be maintained continuously; but if the fire is one which must be increased or diminished to suit the exigencies of household details, nothing but the closest and most careful attention will keep the sponge at uniform temperature. The better way is to cover the bowl with a napkin, and in cold weather wrap closely in several thicknesses of flannel, and place on a stand behind the stove, or in some place not exposed to draughts. A bread-raiser purposely arranged for keeping the bread at proper temperature is a great convenience. Two small and rather thick earthen ware crocks of the same size, serve very well for this purpose. Scald both with hot water, and while still warm, put the sponge in one, invert the other for a cover, and leave in a warm room. All flour used in the bread should be warm when added.