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Page:Popular Science Monthly Volume 25.djvu/652

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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 nation.

 

THE CHEMISTRY OF COOKERY.
By W. MATTIEU WILLIAMS.
XXXIV.

RESPECTING 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 apparently smaller degree of porosity. That this change can be only apparent 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 examination 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 network 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 interstices or spaces between the minute fibers of the cell-walls are diminished by the approximation or adhesion of these fibers to each other.