Fig. 48.—Apparatus Used in Study of Losses in Bread Making.
180. Volatile Compounds produced during Bread Making.—In addition to carbon dioxid and alcohol, there is lost during bread making a small amount of carbon in other forms, as volatile acids and hydrocarbon products equivalent to about one tenth of one per cent of carbon dioxid. The aroma of freshly baked bread is due to these compounds. Both the odor and flavor of bread are caused in part by the volatile acids and hydrocarbons. The amount and kind of volatile products formed can be somewhat regulated through the fermentation process by the use of special flours and the addition of materials that produce specific fermentation changes and desirable aromatic compounds. Some of the ferment bodies left in flour from the imperfect removal of the dirt adhering to the exterior of the wheat kernels impart characteristic flavors to the bread. The so-called nutty flavor of some bread is due to the action of these ferment bodies and, when intensified, it becomes objectionable. Fungous growths in unsound flour and bread result in the liberation of volatile products, which impart a musty odor. Good odor and flavor are very desirable in both flour and bread.
181. Behavior of Wheat Proteids in Bread Making.—Gluten is an ingredient of the flour on which its bread-making properties largely depend. The important thing, however, is not entirely the quantity of gluten, but more particularly its character. Two flours containing the same amounts of carbohydrates and proteid compounds, when converted into bread by exactly the same process, may produce bread of entirely different physical characteristics because of differences in the nature of the gluten of the two samples. Gluten is composed of two bodies called gliadin and glutenin. The gliadin, a sort of plant gelatin, is the material which binds the flour particles together to form the dough, thus giving it tenacity and adhesiveness; and the glutenin is the material to which the gliadin adheres. If there is an excess of gliadin, the dough is soft and sticky, while if there is a deficiency, it lacks expansive power. Many flours containing a large amount of gluten and total proteid material and possessing a high nutritive value, do not yield bread of the best quality, because of an imperfect blending of the gliadin and glutenin. This question is of much importance in the milling of wheats, especially in the blending of the different types of wheat. An abnormally large amount of gluten does not yield a correspondingly large loaf.
Fig. 49.—Bread from Normal Flour (1);
Gliadin Extracted Flour (2);
and from Flour after Extraction of Sugar
and Soluble Proteids (3).
Experiments were made at the Minnesota Experiment Station to determine the relation between the nature of the gluten and the character of the bread. This was done by comparing bread from normal flour with that from other flour of the same lot, but having part or all of its gliadin extracted.[64] Dough made from the latter was not sticky, but felt like putty, and broke in the same way. The yeast caused the mass to expand a little when first placed in the oven; then the loaf broke apart at the top and decreased in size. When baked it was less than half the size of that from the same weight of normal flour, and decidedly inferior in other respects. The removal of part of the gliadin produced nearly the same effect as the extraction of the whole of it, and even when an equal quantity of normal flour was mixed with that from which part of the gliadin had been extracted, the bread was only slightly improved. In flour of the highest bread-making properties the two constituents, gliadin and glutenin, are present in such proportions as to form a well-balanced gluten.
The proteids of wheat flour are mainly in an insoluble form, although there are small amounts of albumins and globulins; these are coagulated by the action of heat during the bread-making process, and rendered insoluble. A portion of the acid that is developed unites with the gliadin and glutenin, forming acid proteids, which change the physical properties of the dough. Both gliadin and glutenin take important parts in bread making. The removal of gliadin from flour causes complete loss of bread-making properties. Ordinarily from 45 to 65 per cent of the total nitrogen of the flour is present in alcohol soluble or gliadin form. Proteids also undergo hydration during mixing, some water being chemically united with them, changing their physical properties. This hydration change is necessary for the full development of the physical properties of the gluten. The water and salt soluble proteids appear to take no important part in the bread-making process, as their removal in no way affects the size of the loaf or general character of the bread. Because of the action of the acids upon the gliadin, bread contains a larger amount of alcohol soluble nitrogen or gliadin than the flour from which the bread was made. It is believed that this action changes the molecular structure of the protein so that it is more readily separated into its component parts when it undergoes digestion and assimilation.
182. Production of Volatile Nitrogenous Compounds.—When fermentation is unnecessarily prolonged, an appreciable amount of nitrogen is volatilized in the form of ammonia and allied bodies, as amids. During the process of bread making, the yeast appears to act upon the protein, as well as upon the carbohydrates, and, as previously stated, losses of dry matter fall alike upon these two classes of compounds, nitrogenous and non-nitrogenous. Analyses of the flours and materials used in bread making, and of the bread, show that ordinarily about 1.5 per cent of the total nitrogen is liberated in the form of gas during the bread-making process, and analyses of the gases dispelled in baking show approximately the same per cent of nitrogen. When bread is dried, as in a drying oven, a small amount of volatile nitrogen appears to be given off,—probably as ammonium compounds formed during fermentation. The nitrogen lost in bread making under ordinary conditions is not sufficient to affect the nutritive value of the product. The losses of both nitrogen and carbon are more than offset by the increased solubility of the proteids and carbohydrates, the preliminary changes they have undergone making them more digestible and valuable for food purposes. The nitrogen volatilized in bread making appears to be mainly that present in the flour in amid forms or liberated as the result of fermentation processes. The more stable proteids undergo only limited changes in solubility and are not volatilized.
183. Oxidation of Fat.—Flour contains about 1.25 per cent of fat mechanically mixed with a small amount of yellow coloring matter. During the process of bread making the fat undergoes slight oxidation, accompanied by changes in both physical and chemical properties. The fat from bread, when no lard or shortening has been added, is darker in color, more viscous, less soluble in ether, and has a lower iodine number, than fat from flour. The change in solubility of the fat is not, however, such as to affect food value, because the fat is not volatilized, and is only changed by the addition of a small amount of oxygen from the air. When wheat fat and other vegetable and animal fats are exposed to the air, they undergo changes known as aging, similar to the slight oxidation changes in bread making.[64]
184. Influence of the Addition of Wheat Starch and Gluten to
Flour.—Ten per cent or more of starch may be added to normal flour
containing a well-balanced gluten, without decreasing the size of the
loaf. When moist gluten was added to flour, thus increasing the total
amount of gluten, the size of the loaf was not increased[67].
Influence of Addition of Starch and Gluten to Flour
| Size of Loaf | Weight | |
|---|---|---|
| Wheat flour, 14 ounces | 22½ × 17½ | 18.75 |
| Wheat flour, 10% wheat starch | 23½ × 17 | 18.25 |
| Wheat flour, 12.2% wheat starch | 21½ × 17 | 18.00 |
| Wheat flour, 210 grams, about 8 ounces | 12¾ × 9 | 12.00 |
| Wheat flour, 10% gluten added, 210 grams | 12½ × 9 | 12.75 |
| Wheat flour, 20% gluten added | 12 × 8¾ | 13.00 |
So long as the quality of the gluten is not destroyed, the addition of a
small amount of either starch or gluten to flour does not affect the
size of the loaf, but removal of the gluten affects the moisture content
and physical properties of the bread. The addition of starch to flour
has the same effect upon the bread as the use of low gluten
flour,—lessening the capacity of the flour to absorb water and
producing a dryer bread of poorer quality.
185. Composition of Bread.—The composition of bread depends primarily
upon that of the flour from which it was made. If milk and butter (or
lard) are used in making the dough, as is commonly the case, their
nutrients are, of course, added to those of the flour; but when only
water and flour are used, the nutrients of the bread are simply those
of the flour. In either case the amount of nutrients in the bread is
smaller than in the same weight of flour, because a considerable part of
the water or milk used in making the dough is present in the bread after
baking; that is, a pound of bread contains less of any of the nutrients
than a pound of the flour from which the bread was made, because the
proportion of water in the bread is greater. The following table shows
how the composition of flour compares with that of bread, the different
kinds of bread all having been made from the flour with which they are
compared:
Composition of Flour, and Bread Made from it in Different Ways
| Material | Water | Protein | Fat | C.H. | Ash |
|---|---|---|---|---|---|
| % | % | % | % | % | |
| Flour | 10.11 | 12.47 | 0.86 | 76.09 | 0.47 |
| Bread from flour and water | 36.12 | 9.46 | 0.40 | 53.70 | 0.32 |
| Bread from flour, water, and lard | 37.70 | 9.27 | 1.02 | 51.70 | 0.31 |
| Bread from flour and skim milk | 36.02 | 10.57 | 0.48 | 52.63 | 0.30 |
Thus it may be seen that the proportion of water is larger and of each
nutrient smaller in bread than in flour, and that the nutrients of the
flour are increased by those in the materials added in making the bread.
It is apparent that two breads of the same lot of flour may differ, according to the method used in making, and also that two loaves of bread made by exactly the same process but from different lots of flour, even when of the same grade or brand, do not necessarily have the same composition, because of possible variation in the flours. In bread made from flour of low gluten content, the per cent of protein is correspondingly low.
186. Use of Skim Milk and Lard in Bread Making.—When flours low in gluten are used, skim milk may be employed advantageously in making the bread, to increase the protein content. Tests show that such bread contains about 1 per cent more protein than that made with water. Ordinarily there is no gain from a nutritive point of view in adding an excessive amount of lard or other shortening, as it tends to widen the nutritive ratio.
187. Influence of Warm and Cold Flours on Bread Making.—When flour is stored in a cold closet or storeroom, it is not in condition to produce a good quality of bread until it has been warmed to a temperature of about 70° F. Cold flour checks the fermentation process, and is occasionally the cause of poor bread. On the other hand, when flour is too warm (98° F.) the influence upon fermentation is unfavorable. Heating of flour does not affect the bread-making value, provided the flour is not heated above 158° F. and is subsequently cooled to a temperature of 70° F. Wheat flour contains naturally a number of ferment substances, some of which are destroyed by the action of heat. The natural ferments, or enzymes, of flour appear to take a part in bread making, imparting characteristic odors and flavors to the product.
Fig. 50.-Bread from (1) Graham, (2) Entire Wheat, and (3) White Flour.
The same amounts of flour were used in making all of the breads.
188. Variations in the Process of Bread Making.—Since flours differ so in chemical composition, and the yeast plant acts upon all the compounds of flour, it naturally follows that bread making is not a simple but a complex operation, resulting in a number of intricate chemical reactions, which it is necessary to control and many of which are only imperfectly understood. Bread of the best physical quality and commercial value is made of flour from fully matured, hard wheats, containing a low per cent of acid, no foreign ferment materials or their products, and at least 12½ per cent of proteids, of which the larger portion is in the form of gliadin. It is believed that a better quality of bread could be produced from many flours by slight changes or modifications in the process of bread making. It cannot be expected that the same process will give the best results alike with all types and kinds of flour. The kind of fermentation process that will produce the best bread from a given type of flour can be determined only by experimentation. Poor bread making is due as often to lack of skill on the part of the bread maker, and to poor yeast, as it is to poor quality of flour. Frequently the flour is blamed when the poor bread is due to other factors. Lack of control of the fermentation process, and the consequent development of acid and other organisms which check the activity of the alcoholic ferments, is a frequent cause of poor bread.
189. Digestibility of Bread.—Extensive experiments have been made by the Office of Experiment Stations of the United States Department of Agriculture, at the Minnesota and Maine Experiment Stations, to determine the digestibility and nutritive value of bread. Different kinds and types of wheat were milled so as to secure from each three flours: graham, entire wheat, and standard patent. The flours were made into bread, and the bread fed to workingmen, and its digestibility determined. The experiments taken as a whole show that bread is an exceedingly digestible food, nearly 98 per cent of the starch or carbohydrate nutrients and about 88 per cent of the gluten or proteid constituents being assimilated by the body. In the case of the graham and entire wheat flours, although they contained a larger total amount of protein, the nutrients were not as completely digested and absorbed by the body as were those of the white flour. The body secured a larger amount of nutrients from the white than from the other grades of flour, the digestibility of the three types being as follows: standard patent flour, protein 88.6 per cent and carbohydrates 97.7 per cent; entire wheat flour, protein 82 percent and carbohydrates 93.5 per cent; graham flour, protein 74.9 per cent and carbohydrates 89.2 per cent. The low digestibility of the protein of the graham and entire wheat flours is supposed to be due to the coarser granulation; the proteins, being embedded and surrounded with cellular tissue, escape the action of the digestive fluids. Microscopic examination of the feces showed that often entire starch grains were still inclosed in the woody coverings and consequently had failed to undergo digestion.[62], [64], [67], [86]
190. Use of Graham and Entire Wheat in the Dietary.—Entire wheat and graham flours should be included in the dietary of some persons, as they are often valuable because of their physiological action, the branny particles stimulating the process of digestion and encouraging peristaltic action. In the diet of the overfed, they are valuable for the smaller rather than the larger amount of nutrients they contain. Also they supply bulk and give the digestive tract needed exercise. For the laboring man, where it is necessary to obtain the largest amount of available nutrients, bread from white flour should be supplied; in the dietary of the sedentary, graham and entire wheat flours can, if found beneficial, be made to form an essential part. The kind of bread that it is best to use is largely a matter of personal choice founded upon experience.
"When we pass on to consider the relative nutritive values of white and whole-meal bread, we are on ground that has been the scene of many a controversy. It is often contended that whole-meal is preferable to white bread, because it is richer in proteid and mineral matter, and so makes a better balanced diet. But our examination of the chemical composition of whole-meal bread has shown that as regards proteid at least, this is not always true, and even were it the case, the lesser absorption of whole-meal bread, which we have seen to occur, would tend to annul the advantage.... On the whole, we may fairly regard the vexed question of whole-meal versus white bread as finally settled and settled in favor of the latter."[28]
"The higher percentage of nitrogen in bran than in fine flour has frequently led to the recommendation of the coarser breads as more nutritious than the finer. We have already seen that the more branny portions of the grain also contain a much larger percentage of mineral matter. And, further, it is in the bran that the largest proportion of fatty matter—the non-nitrogenous substance of higher respiratory capacity which the wheat contains—is found. It is, however, we think, very questionable whether upon such data alone a valid opinion can be formed of the comparative values of bread made from the finer or courser flours ground from one and the same grain. Again, it is an indisputable fact that branny particles when admitted into the flour in the degree of imperfect division in which our ordinary milling processes leave them very considerably increase the peristaltic action, and hence the alimentary canal is cleared much more rapidly of its contents. It is also well known that the poorer classes almost invariably prefer the whiter bread, and among some of those who work the hardest and who consequently soonest appreciate a difference in nutritive quality (navvies, for example) it is distinctly stated that their preference for the whiter bread is founded on the fact that the browner passes through them too rapidly; consequently, before their systems have extracted from it as much nutritious matter as it ought to yield them.... In fact, all experience tends to show that the state as well as the chemical composition of our food must be considered; in other words, that the digestibility and aptitude for assimilation are not less important qualities than its ultimate composition.
"But to suppose that whole-wheat meal as ordinarily prepared is, as has generally been assumed, weight for weight more nutritious than ordinary bread flour is an utter fallacy founded on theoretical text-book dicta, not only entirely unsupported by experience, but inconsistent with it. In fact, it is just the poorer fed and the harder working that should have the ordinary flour bread rather than the whole-meal bread as hitherto prepared, and it is the overfed and the sedentary that should have such whole-meal bread. Lastly, if the whole grain were finely ground, it is by no means certain that the percentage of really nutritive nitrogenous matters would be higher than in ordinary bread flour, and it is quite a question whether the excess of earthy phosphates would not then be injurious."—Lawes and Gilbert.[68]
"According to the chemical analysis of graham, entire wheat, and standard patent flours milled from the same lot of hard Scotch Fife spring wheat, the graham flour contained the highest and the patent flour the lowest percentage of total protein. But according to the results of digestion experiments with these flours the proportions of digestible or available protein and available energy in the patent flour were larger than in either the entire wheat or the graham flour. The lower digestibility of the protein of the latter is due to the fact that in both these flours a considerable portion of this constituent is contained in the coarser particles (bran), and so resists the action of the digestive juices and escapes digestion. Thus while there actually may be more protein in a given amount of graham or entire wheat flour than in the same weight of patent flour from the same wheat, the body obtains less of the protein and energy from the coarse flour than it does from the fine, because, although the including of the bran and germ increases the percentage of protein, it decreases its digestibility. By digestibility is meant the difference between the amounts of the several nutrients consumed and the amount excreted in the feces.
"The digestibility of first and second patent flours was not appreciably different from that of standard patent flour. The degree of digestibility of all these flours is high, due largely to their mechanical condition; that is, to the fact that they are finely ground."—Snyder.[62]
For a more extended discussion of the subject, the student is referred to Bulletins 67, 101, and 126, Office of Experiment Stations, United States Department of Agriculture.
191. Mineral Content of White Bread.—Average flour contains from 0.4 to 0.5 of 1 per cent of ash or mineral matter, the larger portion being lime and magnesia and phosphate of potassium. It is argued by some that graham and entire wheat flours should be used liberally because of their larger mineral content and their greater richness in phosphates. In a mixed dietary, however, in which bread forms an essential part, there is always an excess of phosphates, and there is nothing to be gained by increasing the amount, as it only requires additional work of the kidneys for its removal. Few experiments have been made to determine the phosphorus requirements of the human body, but these indicate that it is unnecessary to increase the phosphate content of a mixed diet. It is estimated that less than two grams per day of phosphates are required to meet all of the needs of the body, and in an average mixed ration there are present from three to five grams and more. A large portion of the phosphate compounds of white bread is present in organic combinations, as lecithin and nucleated proteids, which are the most available forms, and more valuable for purposes of nutrition than the mineral phosphates. In the case of graham and entire wheat flours, a proportionally smaller amount of the phosphates are digested and assimilated than from the finer grades of flour.
192. Comparative Digestibility of New and Old Bread.—With healthy persons there is no difference whatever in the completeness of digestibility of old and new bread; one appears to be as thoroughly absorbed as the other. In the case of some individuals with impaired digestion there may be a difference in the ease and comfort with which the two kinds of bread are digested, but this is due mainly to individuality and does not apply generally. The change which bread undergoes when it is kept for several days is largely a loss of moisture and development of a small amount of acid and other substances from the continued ferment action.
193. Different Kinds of Bread.—According to variations in method of preparation, there are different types and varieties of bread, as the "flat bread" of Scandinavian countries, unleavened bread, Vienna bread, salt rising bread, etc. Bread made with baking powder differs in no essential way from that made with yeast, except in the presence of the residue from the baking powder, discussed in Chapter XII. Biscuits, wheat cakes, crackers, and other food materials made principally from flour, have practically the same food value as bread. It makes but little difference in what way flour is prepared as food, for in its various forms it has practically the same digestibility and nutritive value.
194. Toast.—When bread is toasted there is no change in the percentage of total nutrients on a dry matter basis. The change is in solubility and form, and not in amount of nutrients available. Some of the starch becomes dextrine, which is more soluble and digestible.[5] Proteids, on the other hand, are rendered less soluble, which appears to slightly lower the digestion coefficient. They are somewhat more readily but not quite so completely digested as those of bread. Digestion experiments show that toast more readily yields to the diastase and other ferments than does wheat bread. Toasting brings about ease of digestion rather than increased completeness of the process. Toast is a sterile food, while bread often contains various ferments which have not been destroyed by baking. These undergo incubation during the process of digestion, particularly in the case of individuals with diseases of the digestive tract. With normal digestion, however, these ferment bodies do not develop to any appreciable extent, as the digestive tract disinfects itself. When the flour is prepared from well cleaned wheat and the ferment substances which are present mainly in the bran particles have been removed, a flour of higher sanitary value is secured.
CHAPTER XII
BAKING POWDERS
195. General Composition.—All baking powders contain at least two materials; one of these has combined carbon dioxid in its composition, the other some acid constituent which serves to liberate the gas. The material from which the gas is obtained is almost invariably sodium bicarbonate, NaHCO3, commonly known as "soda" or "saleratus." Ammonium carbonate has been used to some extent, but is very seldom used at the present time. The acid constituent may be one of several materials, the most common being cream of tartar, tartaric acid, calcium phosphate, or alum. These may be used separately or in combination. The various baking powders are designated according to the acid constituent, as "cream of tartar," "phosphate," and "alum" powders. All of them liberate carbon dioxid gas, but the products left in the food differ widely in nature and amount[69].
Baking powder is a chemical preparation which, when brought in contact with water, liberates carbon dioxid gas. The baking powder is mixed dry with flour, and when this is moistened the carbon dioxid that is liberated expands the dough. The action is similar to that of yeast except that in the case of yeast the gas is given off much more slowly and no residue is left in the bread. When baking powder is used, there is a residue left in the food which varies with the material in the powder. It is the nature and amount of this residue that is important and makes one baking powder more desirable than another.
Fig. 51.—Ingredients of a Baking Powder.
1, baking powder; 2, cream of tartar; 3, baking soda; 4, starch.
196. Cream of Tartar Powders.—The acid ingredient of the cream of tartar powders is tartaric acid, H2C4H4O6. Cream of tartar is potassium acid tartrate, KHC4H4O6; it contains one atom of replaceable hydrogen, which imparts the acid properties, and it is prepared from crude argol, a deposit of grape juice when wine is made. The residue from this powder is sodium potassium tartrate, NaKC4H4O6, commonly known as Rochelle salt. This is the active ingredient of Seidlitz powders and has a purgative effect when taken into the body. The dose as a purgative is from one half to one ounce. A loaf of bread as ordinarily made with cream of tartar powder contains about 160 grains of Rochelle salt, which is 45 grains more than is found in a Seidlitz powder, but the amount actually eaten at any one time is small and its physiological effect can probably be disregarded. When a cream of tartar baking powder is used, the reaction takes place according to the following equation:
| 188 | 84 | 210 | 44 | 18 |
| HKH4C4O6 + NaHCO3 = KNaC4H4O6 + CO2 + H2O. | ||||
The crystallized Rochelle salt contains four molecules of water, so that, even allowing for some starch filler, there is very nearly as much weight of material (Rochelle salt) left in the food as there was of the original powder. If free tartaric acid were used instead of potassium acid tartrate, the reaction would be as follows:
| 150 | 168 | 230 | 88 |
| H2C4H4O6 + 2 NaHCO3 = Na2C2H4O6.2 H2O + 2 CO2. | |||
But the residue, sodium tartrate, is less in proportion. It has physiological properties very similar to Rochelle salt. Tartaric acid is seldom used alone, but very often in combination with cream of tartar. It is more expensive than cream of tartar; but not so much is required, and it is more rapid in action.
197. Phosphate Baking Powders.—Here the acid ingredient is phosphoric acid and the compound usually employed is mono-calcium phosphate, CaH4(PO-{4})2. This is made by the action of sulphuric acid on ground bone (Ca3(PO4)2 + 2 H2SO4 = CaH4(PO4)2 + 2 CaSO4), and it is difficult to free it from the calcium phosphate formed at the same time; hence such powders contain more or less of this inert material. The reaction which occurs with a phosphate powder is as follows:
| 234 | 168 | 136 |
| CaH4(PO4)2 + 2 NaHCO3 = CaHPO4 | ||
| 88 | 36 | 142 |
| + 2 CO2 + 2 H2O + Na2HPO4. | ||
Sodium phosphate, according to the United States Dispensatory, is "mildly purgative in doses of from 1 to 2 ounces." The claim is made by the makers of phosphate baking powders that the phosphates of sodium and calcium, products left after the baking, restore the phosphates which have been lost from the flour in the bran. This baking powder residue does not restore the phosphates in the same form in which they are present in grains and it does furnish them in larger amounts—nearly tenfold. However, the residue from these powders is probably less objectionable than that from alum powders. The chief drawback to the phosphate powders is their poor keeping qualities.
198. Alum Baking Powders.—Sulphuric acid is the acid constituent of these powders. The alums are double sulphates of aluminium and an alkali metal, and have the general formula xAl(SO4)2 in which x may be K, Na, or NH4, producing respectively a potash, soda, or ammonia alum. Potash alum is most commonly used, soda and ammonia alums to a less extent. The reaction takes place as follows:
| 475 | 504 | 157 |
| 2 NH4Al(SO4)2 + 6 NaHCO3 = Al2(OH)6 | ||
| 426 | 132 | 264 |
| + 3 Na2SO4 + (NH4)2SO4 + 6 CO2. | ||
If it is a potash or soda alum, simply substitute K or Na for NH4 throughout the equation. The best authorities regard alum baking powders as the most objectionable. Ammonia alum is without doubt the worst form, since all of the ammonium compounds have an extremely irritating effect on animal tissue. Sulphates of sodium and potassium are also objectionable. Aluminium hydroxide is soluble in the slightly acid gastric juice and has an astringent action on animal tissue, hindering digestion in a way similar to the alum itself. Many of the alum powders contain also mono-calcium phosphate; the reaction is as follows:
| 475 | 234 | 336 |
| 2 NH4Al(SO4)2 + CaH4(PO4)2 + 4 NaHCO3 | ||
| 245 | 136 | 132 |
| = Al2(PO4)2 + CaSO4 + (NH4)2SO4 | ||
| 284 | 176 | 72 |
| + 2 Na2SO4 + 4 CO2 + 4 H2O. | ||
These are probably less injurious than the straight alum powders, although the residues are, in general, open to the same objection.
199. Inspection of Baking Powders.—Many of the states have enacted laws seeking to regulate the sale of alum baking powders. Some of these laws simply require the packages to bear a label setting forth the fact that alum is one of the ingredients; others require the baking powder packages to bear a label naming all the ingredients of the powder.
200. Fillers.—All baking powders contain a filler of starch. This is necessary to keep the materials from acting before the powder is used. The amount of filler varies from 15 to 50 per cent; the least is found in the tartrate powders and the most in the phosphate powders. The amount of gas which a powder gives off regulates its value; it should give off at least ⅛ of its weight.
201. Home-made Baking Powders.—Baking powders can be made at home for about one half what they usually cost and they will give equal satisfaction. The following will make a long-keeping powder: cream of tartar, 8 ounces; baking soda, 4 ounces; corn starch, 3 ounces. For a quick-acting powder use but one ounce of starch. The materials should be thoroughly dry. Mix the soda and starch first by shaking well in a glass or tin can. Add the cream of tartar last and shake again. Thorough mixing is essential to good results. Cream of tartar is often adulterated, but it can be obtained pure from a reliable druggist. To insure baking powders remaining perfectly dry, they should always be kept in glass or tin cans, never in paper.
CHAPTER XIII
VINEGAR, SPICES, AND CONDIMENTS
202. Vinegar.—Vinegar is a dilute solution of acetic acid produced by fermentation, and contains, in addition to acetic acid, small amounts of other materials in solution, as mineral matter and malic acid, according to the material from which the vinegar was made. Unless otherwise designated, vinegar in this country is generally considered to be made from apples. Other substances, however, are used, as vinegar can be manufactured from a variety of fermentable materials, as molasses, glucose, malt, wine, and alcoholic beverages in general. The chemical changes which take place in the production of vinegars are: (1) inversion of the sugar, (2) conversion of the invert sugars into alcohol, and (3) change of alcohol into acetic acid. All these chemical changes are the result of ferment action. The various invert ferments change the sugar into dextrose and glucose sugars; then the alcoholic ferment produces alcohol and carbon dioxid from the invert sugars, and finally the acetic acid ferment completes the work by converting the alcohol into acetic acid. The chemical changes which take place in these different steps are:
| sucrose | dextrose | levulose |
| (1) C12H22O11 + H2O = C6H12O6 + C6H12O6; | ||
| dextrose | alcohol |
| (2) C6H12O6 = 2 C2H5OH + 2 CO2; | |
| alcohol | acid |
| (3) C2H5OH + 2 O = HC2H3O2 + H2O. | |
The acetic acid organism, Mycoderma aceti, can work only in the presence of oxygen. It is one of the aerobic ferments, and is present in what is known as the "mother" of vinegar and is secreted by it. When vinegar is made in quantity, the process is hastened by allowing the alcoholic solution to pass through a narrow tank rilled with shavings containing some of the ferment material, and at the same time air is admitted so as to secure a good supply of oxygen. When vinegar is made by allowing cider or wine to stand in a warm place until the fermentation process is completed, a long time is required—the length of time depending upon the supply of air and other conditions affecting fermentation.
Fig. 52.—Acetic Acid
Ferments.
(After
König.)
In some countries malt vinegar is common. This is produced by allowing a wort made from malt and barley to undergo acetic acid fermentation, without first distilling the alcohol as is done in the preparation of spirit vinegar. In various European countries wine vinegar is in general use and is made by acetification of the juice of grapes. Sometimes spirit vinegar is made from corn or barley malt. Alcoholic fermentation takes place, the alcohol is distilled so that a weak solution remains, which is acetified in the ordinary way. Such a vinegar can be produced very cheaply and is much inferior in flavor to genuine wine or cider vinegar.
Vinegar, when properly made, should remain clear, and should not form a heavy deposit or produce any large amount of the fungous growth, commonly called the "mother" of vinegar. In order to prevent the vinegar from becoming cloudy and forming deposits, it should be strained and stored in clean jugs and protected from the air. So long as air is excluded further acetic acid fermentation and production of "mother" of vinegar cannot take place. When the vinegar is properly made and the fermentation process has been completed, the acid already produced prevents all further development of acetic acid ferments. When vinegar becomes cloudy and produces deposits, it is an indication that the acetic fermentation has not been completed.
The national standard for pure apple cider vinegar calls for not less than 4 grams acetic acid, 1.6 grams of apple solids, and 0.25 grams of apple ash per 100 cubic centimeters, along with other characteristics, as acidity, sugar, and phosphoric acid content. Many states have special laws regarding the sale of vinegar.
203. Adulteration of Vinegar.—Vinegar is frequently adulterated by the addition of water, or by coloring spirit vinegar, thus causing it to resemble cider vinegar. Formerly vinegar was occasionally adulterated by the use of mineral acids, as hydrochloric or sulphuric, but since acetic acid can be produced so cheaply, this form of adulteration has almost entirely disappeared. Colored spirit vinegar contains merely a trace of solid matter and can be readily distinguished from cider vinegar by evaporating a small weighed quantity to dryness and determining the weight of the solids. Occasionally, however, glucose and other materials are added so as to give some solids to the spirit vinegar, but such a vinegar contains only a trace of ash[18]. Attempts have also been made to carry the adulteration still further by adding lime and soda to give the colored spirit vinegar the necessary amount of ash. Malt, white wine, glucose, and molasses vinegars when properly manufactured and unadulterated are not objectionable, but too frequently they are made to resemble and sell as cider vinegar. This is a fraud which affects the pocketbook rather than the health. For home use apple cider vinegar is highly desirable. There is no food material or food adjunct, unless possibly ground coffee and spices, so extensively adulterated as vinegar.
Vinegar has no food value whatever, and is valuable only for giving flavor and palatability to other foods, and to some extent for the preservation of foods. It is useful in the household in other ways, as it furnishes a dilute acid solution of aid in some cooking and baking operations for liberating gas from soda, and also when a dilute acid solution is required for various cleaning purposes.
Vinegar should never be kept in tin pails, or any metallic vessel, because the acetic acid readily dissolves copper, tin, iron, and the ordinary metals, producing poisonous solutions. Earthenware jugs, porcelain dishes, glassware, or wooden casks are all serviceable for storing vinegar.
204. Characteristics of Spices.[70]—Spices are aromatic vegetable substances characterized as a class by containing some essential or volatile oil which gives taste and individuality to the material. They are used for the flavoring of food and are composed of mineral matter and the various nitrogenous and non-nitrogenous compounds found in all plant bodies. Since only a comparatively small amount of a spice is used for flavoring purposes, no appreciable nutrients are added to the food. Some of the spices have characteristic medicinal properties. Occasionally they are used to such an extent as to mask the natural flavors of foods, and to conceal poor cooking and preparation or poor quality. For the microscopic study of spices the student is referred to Winton, "Microscopy of Vegetable Foods," and Leach, "Food Inspection and Analysis."
205. Pepper.—Black and white pepper are the fruit of the pepper plant (Piper nigrum), a climbing perennial shrub which grows in the East and West Indies, the greatest production being in Sumatra. For the black pepper, the berry is picked before thoroughly ripe; for the white pepper, it is allowed to mature. White pepper has the black pericarp or hull removed. Pepper owes its properties to an alkaloid, piperine, and to a volatile oil. In the black pepper berries there is present ash to the extent of about 4.5 per cent, it ought not to be above 6.5 per cent; ether extract, including piperine and resin, not less than 6.5 per cent; crude fiber not more than 16 per cent; also some starch and nitrogenous material. The white pepper contains less ash and cellulose than the black pepper. Ground pepper is frequently grossly adulterated; common adulterants being: cracker crumbs, roasted nut shells and fruit stones, charcoal, corn meal, pepper hulls, mustard hulls, and buckwheat middlings. The pepper berries wrinkle in drying, and this makes it difficult to remove the sand which may have adhered to them. An excessive amount of sand in the ash should be classed as adulteration. Adulterants in pepper are detected mainly by the use of the microscope. The United States standard for pepper is: not more than 7 per cent total ash, 15 per cent fiber, and not less than 25 per cent starch and 6 per cent non-volatile ether extract.[71]
206. Cayenne.—Cayenne or red pepper is the fruit pod of a plant, capsicum, of which there are several varieties,—the small-fruited kind, used to make cayenne or red pepper; and the tabasco sort, forming the basis of tabasco sauce. It is grown mainly in the tropics, and was used there as a condiment before the landing of Columbus, who took specimens back to Europe. Cayenne pepper contains 25 per cent of oil, about 7 per cent of ash, and a liberal amount of starch. The adulterants are usually of a starchy nature, as rice or corn meal, and the product is often colored with some red dye.
207. Mustard.—Mustard is the seed of the mustard plant, and is most often found in commerce in the ground form. The black or brown mustard has a very small seed and the most aroma. White mustard is much larger and is frequently used unground. For the ground mustard, only the interior of the seed is used, the husk being removed in the bolting. Mustard contains a large amount of oil, part of which is usually expressed before grinding, and this is the form in which spice grinders buy it. In mustard flour there is: ash from 4 to 6 per cent, volatile oil from 0.5 to 2 per cent, fixed oil from 15 to 25 per cent, crude fiber from 2 to 5 per cent, albuminoids from 35 to 45 per cent, and a little starch. The principal adulterants are wheat, corn, and rice flour. When these are used, the product is frequently colored with turmeric, a harmless vegetable coloring material.
208. Ginger.—Ginger is the rhizome or root of a reed-like plant (Zingiber officinale), native in tropical Asia, chiefly India. It is cultivated in nearly all tropical countries. When unground it usually occurs in two forms: dried with the epidermis, or with the epidermis removed, when it is called scraped ginger. Very frequently a coating of chalk is given, as a protection against the drug store beetle. Jamaica ginger is the best and most expensive. Cochin, scraped, African, and Calcutta ginger range in price in the order given. Ginger contains from 3.6 to 7.5 per cent of ash, from 1.5 to 3 per cent of volatile oil, and from 3 to 5.5 per cent of fixed oil. There is a large amount of starch. The chief adulterants are rice, wheat, and potato starch, mustard hulls, exhausted ginger from ginger-ale and extract factories, sawdust and ground peanut-shells, and turmeric is frequently used for coloring the product. The United States standard for ginger is not more than 42 per cent starch, 8 per cent fiber, and 6 per cent total ash.[71]
209. Cinnamon and Cassia.—The bark of several species of plants growing in tropical countries furnishes these spices. True cinnamon is a native of Ceylon, while the cassias are from Bengal and China. In this country there is more cassia used than cinnamon—cinnamon being rarely found except in drug stores. Cassia bark is much thicker than cinnamon bark. The ground spice contains about 1.5 per cent volatile oil and the same amount of fixed oil, 4 per cent of ash, and some fiber, nitrogenous matter, and starch. Cereals, cedar sawdust, ground nutshells, oil meal, and cracker crumbs are the chief adulterants.
210. Cloves.—Cloves are the flower buds of an evergreen tree that grows in the tropics. These are picked by hand and dried in the sun. In the order of value, Penang, Sumatra, Amboyna, and Zanzibar furnish the chief varieties. Cloves rarely contain more than 8 per cent ash, or less than 10 per cent volatile oil and 4 per cent fixed oil, and 16 to 20 per cent of tannin-yielding bodies. No starch is present. The chief adulterants of ground cloves are spent cloves, allspice, and ground nutshells. Clove stems are also sometimes used and may be detected by a microscopical examination, since they contain many thick-walled cells and much fibrous tissue.
211. Allspice.—Allspice, or pimento, is the fruit of an evergreen tree common in the West Indies. It is a small, dry, globular berry, two-celled, each cell having a single seed. Allspice contains about 2.5 per cent volatile oil, 4 per cent fixed oil, and 4.5 per cent ash. Because of its cheapness, it is not generally adulterated, cereal starches being the most common adulterants.
212. Nutmeg.—Nutmeg is the interior kernel of the fruit of a tree growing in the East Indies. The fruit resembles a small pear. A fleshy mantle of crimson color, which is mace, envelopes the seed. Nutmeg contains about 2.2 per cent ash, 2.5 to 5 per cent volatile oil, and 25 to 35 per cent fixed oil. Mace has practically the same composition. Extensive adulteration is seldom practiced. The white coating on the surface of the nutmeg is lime, used to prevent sprouting of the germ.