Bread is made of flour, water, salt, fat, and sugar. To these ingredients the yeast plant is added. The right treatment of the whole mass gives a loaf of bread of good volume containing cells of definite structure and size.

Bread is a very complex substance. In addition to organic and inorganic materials it contains three substances that show colloidal behavior: the protein, the starch, and the cellulose. The amount of cellulose is quite small, so that it probably plays a very minor role in bread making. The part that different constituents of the flour play in the dough structure has been discussed in the preceding pages. Their part in bread making will not be repeated here, but the proportion of ingredients used, the temperature for handling the dough and for baking, the fermentation, and the importance of manipulation of the dough will be considered.

Chemical and physical tests may be performed on flour and dough, but as yet the only final convincing proof of flour quality for making bread is the baking test.

Temperature. Enzyme activity is very slow at low temperatures and the enzymes are destroyed at high temperatures. Thus for optimum enzyme activity and also for yeast growth in bread dough it is important to keep the dough at definite temperatures.

Fermentation is carried out over a wide range of temperature. The evidence indicates that a low temperature is more desirable from the standpoint of flavor and the development of acetylmethylcarbinol. But fermentation is more rapid at higher temperatures. Temperatures from 26° to 32°C. (79° to 90°F.) are used. There is more danger at higher temperatures for growth of undesirable organisms which produce disagreeable flavors.

Proportion of ingredients used in bread. The American Association of Cereal Chemists (A.A.C.C.) appointed a committee, headed by Fitz, later by Blish and others, to find the proportion of ingredients used by members of the association in test bakes, and to formulate a standard method of procedure and a definite formula for use by members of the association.

Flour. It is customary in computing the percentage of ingredients used in bread to take flour as 100 and compute the proportion of the other ingredients in relation to it. Thus if 112 grams of flour are used and to this is added 65 per cent of water, 72.8 grams of water would be used. It requires about 3/4 pound of flour to produce a pound loaf of bread, though the exact amount depends largely upon the hydration capacity of the gluten.

Yeast. Two types of commercial yeast may be purchased, the compressed and the dry. A cake of compressed yeast contains many yeast plants in an active state. When it is used the yeast plants multiply rapidly, producing a large quantity of carbon dioxide gas, and the fermentation takes place in a short time.

In dry yeast the yeast is mixed with corn meal and dried. The yeast plants are not active, as they are in a dormant state and they are few in number. The yeast needs to be soaked for a short time in warm water and then made into a sponge to give time for the revival and growth of the yeast plants. Therefore it requires a longer fermentation period than compressed yeast.

In addition to the dry and the compressed yeast, two other types of yeast are used by housewives, chiefly farm women, where yeast cakes or bread cannot be delivered every day. A liquid yeast may be used and also a starter. The starter is a portion of the sponge that is saved to start the fermentation of the next baking of bread. Since the sponge or dough contains numerous yeast plants it is used instead of yeast cakes for the adding of yeast plants to the dough. To this starter sugar is added for food for the growth of the yeast during storage.

After yeast is added to the bread a period of time elapses before the bread is baked. This period, the length of which depends upon the proportion of ingredients and the kind of yeast used, is called the fermentation period. Bakers call it "proofing" and housewives "rising."

Amount of yeast. The amount of yeast used in bread may vary in wide proportions. Fitz found that as a general rule bakers use 2 to 3 per cent of yeast, although the amount varies from 1 to 5.88 per cent. For home or school the amount may be increased according to the length of time allowed for the fermentation period.

The following table taken from the pamphlet "Baking Better Bread" by the Washburn Crosby Company gives the amount of yeast to use for different periods of fermentation for straight-dough process.

Amount of yeast

Period of fermentation

Temperature

1 cake of yeast to 1 1/2 cups liquid ....

4 hours 2 hours 1st rising 1 hour 2nd rising 1 hour in pans

80

2 cakes of yeast to 1 1/2 cups liquid . . .

3 hours

1 1/2 hours 1st rising 45 minutes 2nd rising 45 minutes in pans

80

3 cakes of yeast to 1 1/2 cups liquid . . .

2 hours 10 minutes 1 hour 1st rising 15 minutes 2nd rising 35 minutes in pans

80

4 cakes of yeast to 1 1/2 cups liquid . . .

1 hour 25 minutes 1st rising 5 minutes 2nd rising 30 minutes in pans

80

Water. Milk may be substituted for water in bread. It is usually scalded to destroy any bacteria or organisms that may produce undesirable flavors or be detrimental to yeast action. Since milk contains about 12 to 14 per cent solids, a larger proportion of it is added than of water. Water in which potatoes have been cooked is sometimes used for a part of the liquid in bread. Because of the development of rope in hot weather, it is often desirable in home-made bread to add the whey of sour milk during the summer.

The best proportion of water varies with the hydration capacity of the gluten in the particular flour that is being used. The proportion as reported in the literature varies from about 51 to 67 per cent. Good bread flours usually require from 60 to 65 per cent of water. Soft-wheat flours, which have weaker glutens, require a lower proportion of water.

Effect of proportion of water used. The proportion of water used affects the tenacity and extensibility of the gluten and hence the resulting dough.

Bailey and Le Vesconte have found that the extensibility of the dough increased with increasing water content until an imbibition equivalent to 64 per cent of the weight of the flour was obtained. Further increase of water and increased hydration decreased the extensibility of the dough. The following table is from their results with the Chopin extensimeter.

Table 48 Effect of Increasing Water in a Dough (Bailey and Le Vesconte)

Absorption, per cent

Extensibility

Reading for tenacity, millimeters

59

18.65

125.0

60

18.80

122.0

61

18.90

121.0

62

19.50

117.1

63

19.77

114.7

64

21.00

99.7

65

20.96

94.5

66

20.48

94.5

67

19.66

92.3

Swanson and Working have reported in experiments with mechanical modification of the dough, using 340 grams of flour, that the best loaf of bread was produced when 205 to 215 cc. of water was used. In the proportions of water used by them the 205 cc. is equivalent to 60 per cent of the weight of the flour and 215 cc. to 63 per cent. When a smaller amount of water than 60 per cent was used a loaf of poor volume was obtained.

Harrel has also reported that better bread is produced when the amount of water used is sufficient. Table 49 from his results is self-explanatory.

The hydration capacity of different glutens varies, hence the maximum volume with any flour will be obtained with a definite water imbibition for that gluten. With increased swelling beyond the point at which the maximum volume is obtained the gluten becomes more tender and less tenacious, some of the cell walls collapse and coalesce, thus giving a smaller volume. With less swelling than the amount required to produce the maximum volume the tenacity is greater and a smaller volume results. The hydration of the gluten can be so great that there is a limit to the amount of stretching the gluten will stand and a very poor volume is the result.

Sugar. Fitz reports that the average proportion of sugar used by bakers varies from 2 to 5 per cent.

Shortening. Fitz has reported that the amount of shortening used by bakers varies from 0 to 3 1/3 per cent. It is not necessary to add shortening to make good bread, but Whymper states that even a low percentage adds to the keeping quality of the bread, for the bread stales less readily.