the investigation of this subject has not been always undertaken under conditions which are wholly beyond criticism. Many of the investigations have been in the interest of rival baking powder companies, and it is very desirable that this matter should be undertaken in a wholly unbiased way and conducted in such a manner as to lead to results which all will accept. Chemical and physiological investigations, which have even as a remote object the promotion of the sale of one compound and the repression of the sale of another, lose at the outset much of that claim upon the public confidence which such investigations made from a purely scientific point of view should have.

General Statement. In respect of the use of chemical leavening agents in general it may be said that they introduce an extraneous product into the bread which is not likely to promote the health and which, therefore, on general principles should be excluded. On the other hand, large experience has shown that the consumption of bread made by these leavening agents does not produce any general effect upon the public health which is noticeable. This, it is understood, is not any valid argument in favor of the process. It must also be acknowledged that a fermentation of a bread with yeast also introduces extraneous matter into the food, viz., alcohol and congeneric products of fermentation, and hence this process may be open to a certain extent to the same objection as the one above. It is too early yet to formulate definite principles either of inclusion or exclusion of these products, and the purpose of this manual is secured when the general character and effects thereof are briefly outlined.

Composition of Bread.-Because of the many different methods of bread making which are practised it is not possible to give in a chemical form an analysis which would do more than represent in general the character of the bread in common use. For instance, the quantity of water which is found in bread varies greatly and the nature of bread itself must be influenced by the character of the flour from which it is made. The flour depends upon the quality of the wheat used in its manufacture. Hence the same brand of bread prepared in the same way and baked in the same manner must necessarily vary in composition from season to season and even from day to day. It must be understood also that it is a very common custom in the United States to use milk in the mixing of dough, and thus a food product is introduced which of itself is not of constant character. Some bakers use whole milk, others skimmed, and others sour milk.

A very good formula for mixing dough for bread making consists in using the following proportions of ingredients mentioned:

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When properly leavened and kneaded and baked these quantities of materials will make a loaf of bread weighing 2750 grams.

Average Composition of Bread.—In the following tables are given the average composition of bread of different classes. Class I is composed of loaves of the so-called Vienna or French type; Class 2 consists of what is known as home made bread or bread baked at the home and not in the bakery; Class 3 consists of bread made from graham flour; Class 4 consists of bread made largely of rye flour; Class 5 is a second collection of home made bread which may be very properly compared with Class 2; Class 6 consists of bread of miscellaneous origin bought on the open market. The data given represent the mean composition of numbers of samples (Bull. 13, Bureau of Chemistry):

A Typical American High-grade Yeast Bread.-In conjunction with the actual analyses given above it is of interest to combine as many analytical data as can be conveniently secured for the purpose of determining what the average composition of a high-grade typical yeast bread is. This comparison leads to the following composition:

Of the ash mentioned in the above analysis .50 percent may be ascribed to the natural mineral ingredient of flour and 1 percent to added salt.

The chief variations from the typical composition of bread made from high-grade flour are found in the moisture and ether extract. The moisture may rise above 40 percent in breads made of flour rich in gluten or sink to 30 percent or under when flour of an inferior gluten content is employed. The quantity of ether extract depends chiefly upon the amount of milk which is used in the making of bread and the amount of fat employed either in the

bread itself or in greasing the pan in which it is baked. There is great difficulty in extracting a fatty body which has been mixed with a glutinous material like flour. The analytical data, therefore, do not represent in the ether extract all the fat naturally present in the flour plus that added in the making of dough or in baking.

The quantity of moisture in bread may also be determined largely by the time of baking and the temperature of the oven. A bread baked for a long while at a low temperature will be much drier than a bread baked quickly at a high temperature. The high temperature solidifies the exterior of the loaf so as to make it difficult for the interior moisture to escape. By quickly baking the bread the temperature of the interior does not reach so high a temperature as in an oven with a low temperature and a long-continued heat. Standard for Moisture.-The quantity of moisture in bread of standard quality in the District of Columbia may not exceed 31 percent.

The average temperature of the baking oven is about 240° C. (464° F.). Quantity of Sugar in Bread.-The quantity of sugar found in fermented bread is always less than that present in the flour, added in milk, or otherwise introduced in the preparation of the dough. The sugar disappears largely under the influence of the fermentation due to the yeast.

Quantity of Ash.-The quantity of ash in bread is uniformly higher than the content of mineral matter in the flour. This is due to the addition of common salt which is uniformly employed in all bread, and in the case of bread made from baking powder the retention of the mineral residues in the loaf increases to that extent the content of ash. With the exception of the ash, the ether extract or fat, the sugar, and the dry material of bread correspond in quantity to the same materials in the flour from which it is made, except the loss due to the caramelization of the crust.

Acidity of Bread.-The development of the lactic acid ferments is important in regard to hygienic conditions and to palatability. Flour contains practically no acid in a free state, and the acidity of bread is itself due to the changes which take place in its preparation under the influence of the ferments therein. Bread baked in the usual manner after the yeast ferments have exerted their activity shows the presence of acetic acid, lactic acid, and other acids and salts. The acidity of bread adds to its palatability and also, doubtless, to its digestibility. Bread, containing, as it does, a large percentage of protein, is digested in an acid medium. The natural acidity of bread, therefore, must be regarded as beneficial.

Comparative Nutritive Properties of Indian Corn Bread and Wheat Bread. There is a widespread opinion that the products of Indian corn are less digestible and less nutritious than those of wheat. This opinion amounts to a conviction in most European countries, where the products obtained by the milling of Indian corn are not regarded as fit for human

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food in an unmixed state. The above opinion, it appears, has no justification either from the chemical composition of the two bodies or from recorded digestive and nutritive experiments.

A study of the analytical data of the whole grain shows that in so far as actual nutrition is concerned the maize is fully as nutritious as wheat. In respect of its content of fat Indian corn and its direct products easily take precedence of all the other cereals, with the exception of hulled oats. In round numbers Indian corn flour or bread made therefrom contains twice as much fat or oil as wheat, three times as much as rye, twice as much as barley, and nearly as much as hulled oats. In regard to digestible carbohydrates, that is digestible starch, sugar, dextrin, and fiber, Indian corn flour possesses a higher content than hulled oats and almost the same content as wheat. In regard to digestible protein Indian corn has nearly the same quantity as the other leading cereals, except oats. What it lacks, however, in its quantity of protein in so far as nutrition is concerned is more than made up in its excess of fat.

Comparative Digestibility and Nutrition of Wheat and Indian Corn from Experiments Made in South Dakota Station, Bulletin 38.-Pigs were fed with Indian corn and wheat, or rather the ground Indian corn and ground wheat, and it was found that pound for pound there was a greater gain in the case of Indian corn flour than wheat. For 100 pounds of flour fed the average gain with Indian corn was 21.83 pounds and where wheat flour was used 20.79 pounds. These experimental data show that in regard to nutritive properties Indian corn flour cannot be considered inferior to wheat flour. Indian corn bread is particularly well suited for persons engaged in hard manual labor. A ration which is composed largely of Indian corn products and oatmeal is found to be particularly valuable for those engaged in lumbering, harvesting sugar-cane, etc.

Indian Corn Flour Pudding.-Various forms of pudding are prepared from Indian corn flour. Among the most important is that known in the New England States as hasty pudding and in the west and south as mush. A simple method of preparing Indian corn pudding, hasty pudding, or mush is to stir into water, very slowly, the Indian corn flour in such a way as to avoid the formation of lumps. The flour should be sifted into the water either cold or at boiling temperature and the mixture vigorously stirred meanwhile. By this means a thin, uniform paste is secured which is allowed to cook slowly until quite thick in consistence and until all the starch granules are thoroughly disintegrated. The product is improved by allowing to stand. for several hours at near the boiling point after the cooking is finished, provided precautions are taken not to allow the mass to become too solid. This product is eaten hot with butter, milk, or cream, or is much prized when allowed to cool, cut into thin slices and fried. A very important dish for the children

of working people and farmers of the south and west is mush and milk, namely the product above mentioned eaten with skim milk. This mixture forms a palatable and wholesome diet. Various other forms of pudding are made into which Indian corn enters to a greater or less degree.

Composition of Biscuits.-The composition of a biscuit or dry unleavened bread does not differ essentially from that of the ordinary bread except in the content of moisture. The biscuits are usually baked in thin cakes or loaves which become heated throughout and sometimes caramelize throughout a large part of their substance. This favors the expulsion of the greater part of the moisture which the dough originally contained. The average composition of biscuits is shown in the following data:

The above data show that biscuits vary in composition from bread chiefly in their content of moisture and fat or oil. The moisture, as is noted, is very low, while the quantity of fat which the biscuit contains is from 8 to 10 times as great as that contained in flour from which they are made. The salt content and the mineral ingredients of the biscuit are often higher than in bread or flour. Inasmuch as a large quantity of fat and salt are used commonly in the manufacture of biscuits the presence of these bodies cannot in any sense be regarded as an adulteration. In forty-eight samples examined only four were free of notable quantities of added fat. In one case over 16 percent of fat was found, and as it has been shown that all the fat which is added is not extracted by ether it is evident that in this case an amount of fat equal to 20 percent of the weight of the flour may have been used.

It appears, from a study of the composition of biscuits, that it is advisable to use them as a relish or delicacy for eating with cheese, etc., in ordinary daily life, while they become almost a necessity in some form or other in the preparation of emergency rations for marching armies, on shipboard, in logging camps, etc. It is not advisable to employ them in the daily diet to the exclusion of bread. Their nutrient contents have, in comparison with bread, a lower coefficient of digestibility, due largely to the added fat.