THE CHEMISTRY OF COOKERY, 6^7 



This adhesion is probably aided by an oozing out or efflorescence 

 of the vapor held by the fibers, and its condensation on their surfaces. 

 This point, be it understood, is merely hypothetical, as the efflorescence 

 is not visible. 



"When the stale bread is again heated, a general expansion occurs 

 by the conversion of liquid water into aqueous vapor, every grain 

 of water thus converted expanding to seventeen hundred times its 

 former bulk. As this happens throughout, i. e., upon the surface of 

 every one of the countless fibers or particles, there must be a general 

 elbowing in the crowd, breaking up the recent adhesion between these 

 fibers and drawing them all apart in the directions of least resistance, 

 i. e., toward the open spaces of the larger and visible pores, producing 

 that apparent diminution of porosity that I have observed as the visi- 

 ble characteristic of the change. 



This explanation of the change may be further demonstrated by 

 cutting a loaf through the middle from top to bottom, and exposing 

 the cut surfaces. In this case the bread becomes unequally stale, more 

 so near the cut surface than within. The unequal pull due to the 

 greater adhesive approximation of the fibers and small particles causes 

 a rupture of the exposed surface of the crumb, which becomes cracked 

 or fissured without any perceptible alteration of the size of the visible 

 pores. If the two broken faces be now accurately placed together, the 

 halves thus closely joined, firmly tied together, and placed for an hour 

 in the oven, it will be seen on separating them that the chasms are con- 

 siderably closed, though not quite healed. Careful examination of the 

 structure of the inside, by breaking out a portion of the crumb, will 

 reveal that loosening of the structure which I have described. 



I should add that, in quoting the figures given by Boussingault in 

 my last, I inadvertently omitted to reduce them from the French to 

 the English thermometric scale : 130° to 150° centigrade is equal to 

 266° to 302° Fahr., which is considerably below the temperature re- 

 quired for starting the original baking. 



" Popped corn " is a peculiar example of starch-cookery. Here a 

 certain degree of porosity is given to an originally close-compacted 

 structure of starch by the simple operation of explosive violence due 

 to the sudden conversion into vapor of the water naturally associated 

 with the starch. The operation is too rapid for the production of much 

 dextrin. 



As most of my readers doubtless know, peas, beans, lentils, and 

 other seeds of leguminous plants are more nutritious, theoretically, 

 than the seeds of grasses, such as wheat, barley, oats, maize, etc. I 

 was glad to see at the Health Exhibition a fine series of the South 

 Kensington cases displaying in the simplest and most demonstrative 

 manner the proximate analyses of the chief materials of animal and 

 vegetable food. I refer to them now because they do not receive the 

 attention they deserve. On the opening day there was, out of all the 



