Gluten

Gluten is separated in the process of making starch from wheat and other grains. It is a valuable nitrogenous food product, consisting of (a) 60 to 70 per cent gliadin and (b) 30 to 40 per cent glutenin. The greater part of the gluten is held in the central four fifths of the grain. The gliadin adheres to the glutenin, retains the gas in dough, and in excess it makes the flour soft and sticky, hence soft wheat yields a flour with high percentage of gliadin, but hard wheat has a low percentage.

Gluten is capable of considerable expansion independently of the development of COz, and, as this power varies with different flours. it affects-the quality of lightness of the bread. Some glutens expand four or five times as much as others (H. Snyder and L. A. Voor-hees).

Composition Of Bread

Bread is really a mixed food, in that it contains so many classes of ingredients - fat, protein, salts, sugar, and starch - and this is probably the explanation of the fact that its daily use never cloys the appetite. Although it contains some fat, it has not enough for a perfect food, and hence the almost universal custom of using butter with it. Moreover, it forms a convenient vehicle for taking fat in this manner, and the butter aids in the mastication and deglutition of the bread.

Good bread contains, on the average, protein, 9.57 per cent; fat, 1.5 to 2 per cent; and carbohydrates, 55 per cent, the remainder being largely water, with a trace of salts. In round numbers, bread contains about two thirds nutrient material, or twice as much as beef, although it is of different force value in the body. One hundred grammes furnish 216 calories. A pound of bread is made from about three quarters of a pound of flour by the addition of 25 per cent of water. Some flours will take up 10 per cent more water (Snyder and Voorhees).

Bread-Baking

Bread is made from a mixture of the flour of any cereal with water, which is added in definite proportion, constituting a dough which is made uniform by kneading either by hand or by machinery. A small quantity of the ferment yeast is also worked uniformly into the dough and the mass is left to stand for a number of hours, during which fermentation progresses, producing from the starch alcohol, carbonic acid, and water. The best temperature at which this leavening proceeds is from 100° to 110° F. After remaining for some hours at a uniform temperature, the bread is baked in a hot oven the temperature of which is sufficient to kill the yeast germs and check further fermentation.

Of all the cooking processes now in use by civilised man, the baking of bread is, perhaps, the most important. The object of cooking flour in this manner is to make it light and porous, so that the digestive fluids may be easily incorporated with it. Flour eaten alone forms a glutinous or sticky mass which is quite indigestible and difficult to swallow, besides being comparatively tasteless. There are many variations in the process of bread-making, but all are based upon the same principle - the development of carbonic-acid gas throughout the mass of dough, which bubbles up and causes it to "rise" or forces it apart. In general, the process involves a loss of about 1 per cent of C02 and 1 per cent of alcohol. The loss of volatile products represents a loss of but 1.58 per cent of starch. Of the remaining starch less than 8 per cent is converted into soluble form (dextrin), but many of the starch granules are ruptured or disintegrated. A very small percentage of fat also disappears in the process of baking.

Development Of Carbonic-Acid Gas

Carbonic-acid gas may be generated or introduced in four ways: I. Indirectly by natural fermentation excited by the addition of the yeast fungus, Torula or Saccharomycetes cerevisice. II. By the use of " leaven," a name given to old dough in which fermentation has already occurred. III. By the addition of baking powders. IV. Directly by "aëration".