Science in the Kitchen / A Scientific Treatise On Food Substances and Their Dietetic Properties, Together with a Practical Explanation of the Principles of Healthful Cookery, and a Large Number of Original, Palatable, and Wholesome Recipes

by E. E. Kellogg

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 mass, 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 mass, 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 mass 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a sufficient crust is formed to retain the air and form a framework of support for the dough, the heat is lessened or withdrawn, the air will escape, or contract to its former volume, allowing the distended glutinous cell walls to collapse; in either case the bread will be heavy.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 mass, 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 aërated 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 class 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 quantity 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.