Length of fermentation period. The total length of the fermentation period depends upon the proportion of yeast used and the temperature at which the sponge or dough is kept. The first rising should double in bulk and should spring back easily when pressed with the finger. It is usually given the longest period and often requires 70 per cent of the total fermentation time. The dough is then punched and worked lightly to allow the gas to escape. The second rising requires a shorter time than the first one, and the dough may be punched and molded and placed in the pans. Very strong glutens may be allowed to rise a third time before putting in the pan.

Dunlap has reported that, with a high initial hydrogen-ion concentration, or induced acidity, produced by the addition of acid or some substance that increases the acidity, better bread is secured if the fermentation periods are reversed, that is the first rising period is short, and the second longer.

If the dough is baked before fermentation has progressed far enough, the resulting bread has thick cell walls and is decidedly less tender than bread fermented sufficiently. The volume is also smaller. This is because the gluten with the proper length of fermentation becomes more dispersed and tender. If fermentation is carried too far the gluten becomes too soft to retain all the expanding gas bubbles and several cells coalesce, which produces thick cell walls and coarse texture. With extreme fermentation the dough smells sour, and a very coarse, heavy, compact bread of small volume and sour taste is obtained.

Prevention of crust formation during fermentation. Drying of the crust may be partially or wholly prevented by covering, keeping in a cabinet with high humidity, or greasing the crust.

A crust formed after the dough is panned gives a dry layer on top that is less elastic. Often a layer of compact grained cells is formed just below the crust because of the drying of the crust, and as a result it is inelastic. The drying in the pan may be prevented in the same way as during rising, or the crust may be moistened with water occasionally.

Size of pan. The volume of the loaf and the shape of cells of the bread depend upon the method of panning and the relation of the amount of dough to the size of the pan.

When the dough is placed on one side of the pan so that it has to turn over in rising the volume is reduced and the loaf is likely to crack in the center from pressure. The dough should be placed in the middle of the pan and shaped so that it is uniform. Harrel found that, with conditions otherwise standardized, a loaf placed slightly to the side of the pan gave a volume of 2700 cc. but placed in the middle of the pan gave a volume of 3230 cc.

Lewis and Whitcomb in their investigations on the "Influence of Size and Shape of Pan on Baking Test" concluded that the purpose for which the pan is intended should govern its shape and size. An experimental bake is a test of the strength of the flour; for this purpose a pan should be used that puts a more severe test upon the flour. Their conclusions are as follows. "The shape of the pan exerts a marked influence upon the size and quality of the loaf in both strong and weak flours.

"The proof period varies with different types of pans. It does not correspond closely with volume or height of loaf or quality of bread.

"Deeper pans produce taller loaves, but not the larger loaves.

"The deep type of pan produces a smaller loaf of somewhat poorer quality than the shallow type. Hence a flour that will produce a good loaf in a deep pan can be depended upon to perform well in the bake shop where the shallow type of pan is used."

The committee on standard formulas and procedure of A.A.C.C. have suggested a pan of the following dimensions for a pound loaf of bread for an experimental bake. Top 7 1/2 by 4 1/2, bottom 7 by 3 1/2, height 3 1/2 inches.

Temperature and time of baking. The 1926-27 committee on baking, Blish, chairman, of A.A.C.C. have recommended baking a pound loaf of bread for 35 minutes at a temperature of 220°C. For the small loaf made with 100 grams of flour they recommend 25 minutes at 220°C. Larger loaves of bread will require a longer baking period and better results will be obtained with a lower baking temperature. The baking temperature depends somewhat upon the volume attained during rising. If the volume is great enough the temperature should be high; if the bread is not proofed quite enough a lower temperature will allow it to rise more in the oven.

Flavor of bread. Visser't Hooft and de Leeuw have reported that excellent flavor in bread is caused by two factors. One factor is a blend of the flavors of the various ingredients of the bread and the other is diacetyl, an important flavor constituent of butter. Acetylmethylcarbinol is formed in the dough as a by-product of fermentation of sugar by yeast. In the finished loaf acetylmethylcarbinol slowly oxidizes to diacetyl. But the amount of acetylmethylcarbinol formed depends upon many factors. The following are reported to have a favorable influence: high sugar-yeast ratio, diastase preparations, low fermentation temperature, short fermentation time, sponge-dough method, hydrogen acceptors or oxidizing agents, oxygen, and proper yeast selection.

The use of soft-wheat flour in bread making. There is a large production of soft-wheat flour in some sections of the United States. Winter wheat, by which is meant wheat planted in the fall, is often called soft wheat. There are two types of winter wheat, one of which produces a soft-wheat flour and the other a hard-wheat flour. The type produced depends upon the place grown and the variety of wheat. Soft wheat is more generally grown in the southern states and soft-wheat flour is used extensively in the South.

Soft-wheat flour can be used in baking bread, but the manipulation required is different from that for strong-wheat flour. The gluten in soft-wheat flour is less colloidal, more dispersed, than in strong-wheat flour. Since fermentation produces greater dispersion of the gluten, which gives greater elasticity, and a more tender gluten, the fermentation period is necessarily shorter for soft-wheat flour than for strong-wheat flour. Better results are also obtained if the proportion of yeast is increased. With increased yeast the sugar is usually increased, as it furnishes a quick food supply for the yeast. Soft-wheat flours do not have so high a hydration capacity as strong wheat, so that it is necessary to use a smaller proportion of liquid. A shallow pan gives better results than a deep one.