Bread is a form of food made from the meal or flour of certain grains.

The word is derived from the verb "to bray or pound," expressive of the old method of preparing the grain. Bread is therefore made of something brayed, as brayed wheat or corn. The brayed grain is moistened and made into dough; various substances are used to raise the dough, and the raised mass is stiffened by the heat in cooking, and thus held in shape, and becomes a loaf.

Bread is made principally from wheat flour, because wheat is the only grain which contains the right proportion of gluten essential to the making of light, spongy bread. Rye used alone makes a moist, close, sticky bread. Corn meal alone makes too dry and crumbly a loaf, but either of these grains may be used to advantage with wheat.

The gluten of wheat is a tough, gray, elastic substance, consisting chiefly of vegetable fibrin. It will swell to four or five times its original bulk. Wheat also contains a large amount of starch, and more mineral matter than any other grain. When the whole of the nutritious part is used, wheat is the most useful food we have, but fine white flour contains only a portion of the desirable elements.

Bread is sometimes made by using soda and an acid to make the dough light; but these mixtures are usually baked in small forms, and called biscuit, muffins, etc. In all these methods there is no chemical change in the flour; the dough is simply made light by the gas from the soda.

But the perfect loaf of light, spongy bread is made by a process quite unlike anything we have studied about, and that is, by the addition of a ferment which causes chemical changes in the flour.

A ferment is some albuminous substance in a state of change or decomposition, and when introduced under proper conditions into any other albuminous substance, in however minute a quantity, causes a change or fermentation in the whole mass.

The germs of these ferments are always present in the air, and when any substances which are rich in sugar, starch, and gluten are exposed to air, warmth, and moisture, these ferments cause a change by which new compounds are formed.

There are several kinds of fermentation. Lactic fermentation is the change in milk when it sours.

Alcoholic fermentation is the change in fruit juices when preserves ferment, or when wine is made from grape-juice, cider from apple-juice, and beer from grains.

Acetic fermentation is caused by allowing alcoholic fermentation to go on too long, or in too warm a place, as when cider changes to vinegar.

In lactic and acetic fermentation, a sour taste is developed ; but in alcoholic fermentation, if not carried too far, there is no unpleasant taste, since the acid produced is carbonic acid gas, which goes off into the air; and as a large amount of carbonic acid gas is formed, this kind of fermentation is most suitable for bread making; theobject being not to produce alcohol, but to puff up the dough and make the bread light.

Wheat flour contains starch and gluten, and a ferment called diastase, and if moistened and kept warm it would in time change, or ferment; but when this change takes place slowly the dough will be sour. This change may be hastened by the addition of a ferment or some albuminous substance which has already begun to change, and which will leave no unpleasant taste. The ferment commonly used is yeast.

Yeast, in its natural state, when viewed under the microscope is found to be a plant or germ of the fungus tribe, of which mould, mildew, etc., are familiar forms. It is one of the simplest and smallest forms of vegetable life. Each little cell has an albuminous skin or membrane, and contains liquid or sap. These cells are found in fruit juices and sprouting grains, and they bud off from each other, and expand rapidly when they are exposed to air and warmth, and in this change or growth they decompose the sugar. But they can be made to grow even more rapidly, and this is what happens when yeast, which is made from sprouting grains, is added to anything containing starch or sugar. Grains which contain starch and gluten are moistened and left for these ferment germs or yeast cells to grow for a while; then the fermentation is checked, and they are prepared in various ways for keeping, and sold under the forms of dry, liquid, and compressed yeast. But the life of the yeast cells is not destroyed, and they will grow again when exposed to warmth and moisture, and given food to live upon ; the same as other forms of vegetable life, after being kept for a time, will grow when planted in proper soil. The temperature of boiling water will kill the yeast plant, and so we must be careful, in using yeast, to have the proper temperature. In making bread, we put yeast with the flour, moisten it, keep it warm, and we have just the food and conditions necessary to waken the yeast plant into life again. The yeast cells begin to grow in the dough, and in thus growing they cause a change in the flour. The diastase ferments and causes some of the starch to change into a kind of sugar; the sugar changes into carbonic acid gas and alcohol. In converting the starch into sugar in the dough, there is no change evident to the eye, but as soon as the sugar is changed to carbonic acid gas and alcohol, large bubbles of gas appear. The gas, being lighter than the dough, rises, and in its efforts to escape puffs up the gluten, and as the gluten is very elastic it can stretch to several times its original ^ulk. It is on account of the peculiar tenacity or power of the wheat gluten to hold the gas that wheat flour makes the lightest bread. The gas fills the dough with minute air cells, which - if the yeast have been uniformly mixed with the flour - make it light and spongy. When this expansion has reached the desired limit, - that is, before the alcoholic fermentation has changed to the acetic and soured the dough, or the tough, glutinous walls of the air cells are broken, making large, unequal holes, - we check the fermentation by baking the dough in a hot oven. The alcohol escapes into the oven, the starch is swollen and ruptured, and absorbs water, some of the starch is changed to gum and forms the crust, which by the intense heat assumes a brown color.

In yeast bread the chemical change in some of the starch is similar to the change which takes place in

starch during digestion, namely, its conversion into sugar. This gives a sweet, nutty flavor and a light, spongy texture, very different from those of soda bread. It is, when properly made and baked, usually considered the most wholesome form of bread.