636 THE POPULAR SCIENCE MONTHLY, 



If, as a result of several seasons' practical operations, it shall be clearly 

 shown that sugar can be profitably made from sorghum, an industry 

 will speedily be established which will furnish employment for much 

 labor and capital, and will add large sums to the wealth of this na- 

 tion. 



THE CHEMISTEY OF COOKEEY. 



By W. MATTIEU WILLIAMS. 

 XXXIV. 



EESPECTING the rationale of the change that takes place in 

 reheating stale bread, thereby renewing it and making it appear 

 moist by actually driving away some of its moisture, the results of my 

 investigations are as follow : 



I find that, as bread becomes stale, its porosity appears to increase, 

 and that, when renewed by reheating, it returns to its original appar- 

 ently smaller degree of porosity. That this change can be only appar- 

 ent is evident from the facts that the total quantity of solid material 

 in the loaf remains the same, and its total dimensions are retained 

 more or less completely by the rigidity of the crust. I say " more or 

 less," because this depends upon the thickness and hardness of the 

 crust, and also upon the completeness of its surrounding. Lightly- 

 baked loaves shrink a little in dimensions in becoming stale, and partly 

 regain the loss on reheating, but this difference only exaggerates the 

 apparent paradox of varying porosity, as the diminished bulk of a 

 given quantity of material displays increased porosity, and the increase 

 of total dimensions accompanies the diminished porosity. 



A reconciliation of this paradox may be obtained by careful exami- 

 nation of the structure of the crumb. This will show that the larger 

 or decidedly visible pores are cells having walls of somewhat silky 

 appearance. This silky luster and structure is, I have no doubt, due 

 to a varnish of dextrin, the gummy nature of which I have already 

 described. Now look a little more closely at this inner surface of the 

 big blow-holes with the aid of a hand-lens of moderate power. It is 

 not a continuous varnish of gum, but a net- work or agglomeration of 

 gummy fibers and particles, barely touching each other. 



My theory of the change that takes place as the bread becomes 

 stale is that these fibers and particles gradually approach each other 

 either by shrinkage or adhesive attraction, and thus consolidate and 

 harden the walls of each of the millions of visible pores, i. e., the solid 

 material of which the loaf is made up. In doing so they naturally 

 increase the dimensions of these visible pores, while the invisible inter- 

 stices or spaces between the minute fibers of the cell-walls are dimin- 

 ished by the approximation or adhesion of these fibers to each other. 



