This section is from the book "Experimental Cookery From The Chemical And Physical Standpoint", by Belle Lowe. Also available from Amazon: Experimental cookery.
Davis and Cline have reported that the best results are obtained with a short fermentation period. They state, "The best results were obtained by allowing the dough to double its volume for the first rising, the bread is then panned, and allowed to treble its volume in the pan." The trebling of the volume in the pan "overcomes the close, cake-like texture and small volume."
Liquid. Davis and Cline state that "To a certain point loaf volume and loaf weight increase with an increase in the proportion of liquid used." A more open porous structure is obtained with increased water; with too high a percentage of water the texture becomes too coarse. With the flour used by Davis and Cline, they have found that 52 per cent of water gives the best loaf and texture. This proportion of water gives a dough so soft that it is necessary to handle it quickly to prevent its sticking to the bread board and hands during the kneading and molding.
Yeast. The quantity of yeast used for soft-wheat bread is increased from 2 to 3 times the amount used in the formula for strong-wheat flour. This requires 1 1/2 to 2 cakes of yeast for a pound loaf of bread.
Sugar. Davis and Cline state that increase of sugar with soft-wheat flours gives a loaf with excellent oven spring, with a silky, spongy, moist texture, for the increased sugar seems to have a toughening action on the gluten. The loaf browns better in the oven with the increased sugar. They have decided that 17 grams, about 1 1/2 tablespoons, for a pound loaf, gives the best results. A larger proportion of sugar, 25 to 35 grams or 2 to 3 tablespoons, yields a loaf of larger volume, but the bread is too sweet.
Salt. Salt retards fermentation and depresses the hydration capacity of gluten. Davis and Cline have reported that 5 grams or about 1 teaspoon for a pound loaf produces the best results for soft wheat. Increasing the quantity increases the length of time required for fermentation and gives a more compact, tough loaf.
Shortening. Two teaspoons per pound loaf produced good results but Davis and Cline have found that increasing the fat to 1 or 1 1/2 tablespoons gives an increased volume and sheen but also requires a longer fermentation.
The staling of bread. Aside from the organoleptic means of detecting staling, several methods have been used by investigators. Karacsonyi has reported the use of the viscosimeter for this purpose. Platt summarizes these methods and reviews the literature on staling. When soaked in an excess of water stale bread does not swell to the extent that fresh bread does. When viewed with the microscope the starch granules in stale bread have a more distinct outline, and often an air space occurs between the starch and gluten. The water extract from fresh bread contains more soluble starch products than that from stale bread. Fresh bread is more elastic than stale bread, hence measuring the compressibility is also a means of determining the degree of staling.
Staling includes all the changes taking place during the storage of bread, cake, pastry, etc. These changes include volatile losses, changes that may be due to oxidation, and most important, changes that occur within the product, which Platt terms "inherent staling."
The volatile losses are largely composed of water, but include small amounts of carbon dioxide, alcohol, acetic acid, diacetyl, and other sub-stances, all of which give the distinctive aroma to fresh bread. The moisture loss can be largely prevented.
Even if moisture loss is prevented from a loaf of bread certain changes take place within the loaf which give it a flinty feel and a crumbly texture. Colloidal systems change slowly and temperature may have a decided effect on the change. In baking, as the gelatinization temperature of the starch is reached, the starch swells, absorbing whatever moisture it can obtain; but the gluten may lose moisture. However, as the bread cools part of the starch is precipitated and releases moisture, which may be absorbed by the gluten or become the source of the dampness of wrapped cool bread. The staling process is reversible, i.e., the stale bread when heated again to a high temperature acquires the characteristics of fresh bread. This reversal can be repeated several times or until the bread has lost too large a proportion of moisture. Though both starch and protein play a role in staling, more work has been done in studying the part starch plays than that of the protein.
Not all the starch is gelatinized in baking, so that the freshly baked bread is not entirely transparent, but has more of a transparent appearance than stale bread. Bryant has reported the following percentage of soluble extract in one experiment: for dry flour after mixing 9.32 per cent, after proofing 10.52 per cent, 30 minutes after baking 13.82 per cent, 6 hours after baking 13.46 per cent, 24 hours after baking 11.92 per cent, and 70 hours after baking 10.41 per cent. He adds that the effect of fat in bread in preventing staleness is not known, but that salt is supposed to tend to increase the staling in that starch changes more rapidly to insoluble starch if salt is present.
Katz, between 1912 and 1916, made extensive investigations concerning the causes of bread becoming stale and means of preventing staling. He refers to staling as follows: "I concluded that staling may be ascribed to an alteration of the starch, partly gelatinized by the baking process, whereby the water-combining powers of starch are impaired or diminished. As a result, starch and the gluten skeleton are no longer in equilibrium with each other, the gluten taking up a certain quantity of water yielded by the starch. The individual starch granules shrink somewhat and relax their union with the gluten skeleton which binds the partly gelatinized starch granules into a uniform whole. The loosening of this union is the basic cause of bread crumbling when the latter becomes stale.
"It is known that another change takes place in the bread crumb when staling, namely, a hardening of the crumb. This change occurs even when loss of water on the part of the whole bread is precluded, which of the two processes will predominate, i.e., hardening or crumbling, depends on the nature of the bread."
Katz and Vershaffelt have found that microscopic studies of fresh and stale bread show differences in the appearance of the starch granules. "In the stale bread the starch granules are more sharply contoured. Upon closer examination it was found that they were doubly contoured and that between the two contours there was a fine air bubble. This distinction between fresh and stale bread can be detected invariably in all types of bread."
Katz has also reported that hardening of the crumb occurs before crumbling. For determining hardness of the crumb a special type of tester is used. The hardness is determined from the number of millimeters that a disc of 22.5-mm. diameter penetrated into the bread crumb, when loaded with a definite weight and allowed to act for a definite time.
If the bread is kept at a temperature of 60°C. or above, and if moisture loss and condensation of water are prevented, the bread stays fresh indefinitely. Thus staling is brought about by cooling of the bread. Katz has reported that at 60°C. or above freshness of the bread is retained, at about 40°C. it becomes approximately half stale, at 30°C. it becomes still more stale, and at 17° to 0°C. it becomes totally stale. But although at 0°C. bread stales quickly, more intense cold inhibits staling. Katz recommends intense cold, - 8°C. or lower, as one means of preventing staling of bread. The chief objection to its use in bakeries is the cost.
Storing the bread from 40° to 60°C. inhibits staling; the chief objection to storing bread at these temperatures is that bacterial and mold growth may be favored.
Whymper states that "The effect of freshness can be enormously increased and sustained for many days by the addition of small quantities of fat to the bread," and that the effect of fat on staleness is out of all proportion to the amount used.
Whymper also states that staleness is hindered by increasing gluten in bread, or at least the addition of gluten to bread delays staleness. Bread made from milk stales more slowly than that made from water. Whymper suggests that fat and gluten prevent the deposition of starch in much the same way as they oppose the setting of cement.
Ropy bread. So-called rope in bread or ropy bread is caused by B. mesentericus, accidentally introduced into the bread through the flour or other means. The spores of this bacteria are not destroyed by baking the bread. Two or three days after baking, and particularly during hot weather, the center of the loaf acquires a peculiar gummy, sometimes crumbly texture, which spreads to the edges of the loaf. The development of rope can be prevented by increasing the acidity of the bread. Thus the whey of sour milk can be used for the liquid in home baking or vinegar can be added. It has been reported that only about 1 per cent of vinegar is required. Other suggestions are to have materials and flour bins scrupulously clean, to increase the amount of yeast, thus shortening the fermentation period, to avoid low temperatures during fermentation, and to cool the baked loaf rapidly.