8zo THE POPULAR SCIENCE MONTHLY. 



As we all know, the flavor and appearance of a boiled sole or mack- 

 erel are decidedly different from those of a fried sole or mackerel, and 

 it is easy to understand that the different results of these cooking pro- 

 cesses are to some extent due to the difference of temperature to which 

 the fish is subjected. 



The surface of the fried fish, like that of the roasted or grilled 

 meat, is " browned." What is the nature, the chemistry of this brown- 

 ing? 



I have endeavored to find some answer to this question, that I 

 might quote with authority, but no technological or purely chemical 

 work within my reach supplies such answer. Rumford refers to it as 

 essential to roasting, and provides for it in the manner already de- 

 scribed, but he goes no further into the philosophy of it than admit- 

 ting its flavoring effect. 



I must therefore struggle with the problem in my own way as I 

 best can. Has the gentle reader ever attempted the manufacture of 

 " hard-bake," or " toffy," or " butter-scotch," by mixing sugar with 

 butter, fusing the mixture, and heating further until the well-known 

 hard, brown confection is produced ? I venture to call this fried sugar. 

 If heated simply without the butter it may be called baked sugar. 

 The scientific name for this baked sugar is caramel. 



The chemical changes that take place in the browning of sugar 

 have been more systematically studied than those which occur in the 

 constituents of flesh when browned in the course of ordinary cookery. 

 Believing them to be nearly analogous, I will state, as briefly as pos- 

 sible, the leading facts concerning the sugar. 



Ordinary sugar is crystalline, i. e., when it passes from the liquid 

 to the solid state it assumes regular geometrical forms. If the solidifi- 

 cation takes place undisturbed and slowly, the geometric crystals are 

 large, as in sugar-candy ; if the water is rapidly evaporated with agi- 

 tation, the crystals are small, and the whole mass is a granular aggre- 

 gation of crystals, such as we see in loaf-sugar. If this crystalline 

 sugar be heated to about 320 it fuses, and without any change of 

 chemical composition undergoes some sort of internal physical altera- 

 tion that makes it cohere in a different fashion. (The learned name 

 for this is allotropism, and the substance is said to be allotropic, other 

 conditioned ; or dimorphic, two-shaped.) Instead of being crystalline 

 the sugar now becomes vitreous, it solidifies as a transparent amber- 

 colored glass-like substance, the well-known barley-sugar, which differs 

 from crystalline sugar, not only in this respect, but has a much lower 

 melting-point ; it liquefies between 190 and 212, while loaf-sugar 

 does not fuse below 320. Left to itself, vitreous sugar returns gradu- 

 ally to its original condition, loses transparency, and breaks up into 

 small crystals. In doing this, it gives out the heat which during its 

 vitreous condition had been doing the work of breaking up its crystal- 

 line structure, and therefore was not manifested as temperature. 



