Experimental cookery

Katz, between 1912 and 1916, made extensive investigations concern- ing 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 438 FLOUR AND BREAD 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 be- tween 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 crum- bling. 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 indefi- nitely. 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 recom- mends 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 objec- tion 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 in- creased 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 pro- portion 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.