12 



Flavor. — The development of the flavor of cured tobacco has not yet 

 been explained. At first a decided flavor of cucumbers^ is generated, 

 which later on is entirely replaced by the rank and common straw 

 smell of cured tobacco, giving rise finally to the superior tobacco flavor 

 developed by the sweating or fermentation process. 



Color. — As regards the brown color of cured and fermented tobacco, 

 there can hardly be any doubt that not only one but several compounds 

 contribute by their chemical changes to its development. Of course 

 the first supposition would be that the tannin, by being changed into 

 a phlobaphene (a brown product), is the principal cause.^ Thus, for 

 exami)le, in the autumn, when the leaves of oaks and of various other 

 trees containing tannin die off, a brown coloration sets in. But the 

 intensity of the brown color of the fermented tobacco leaf does not run 

 parallel to the different concentration of the tannin in the cell systems 

 of the leaf. A healthy tobacco leaf was placed with its base in a dilute 

 solution of ferrous sulphate (about 1 per cent) for from twelve to fifteen 

 hours, at the end of which time this reagent had risen to the tip of the 

 leaf, thereby partly killing it. A reaction in the form of a black color 

 appeared, principally in the ei^idermis and to some extent also in the 

 mesophyll, but not at all in the vascular bundles. This black coloration 

 seemed to be restricted to the chloroplasts. 



The epidermis of cured leaves, however, contains tlie least amount of 

 coloring matter and is sometimes entirely devoid of it, with the excep- 

 tion of the gland hairs, while the mesophyll cells always contain a brown 

 substance in irregular-shaped or rounded masses. The principal jjart 

 of the brown matter, however, is in the veins of the leaves and even the 

 most minute ramifications of the vascular bundles appear to be a much 

 darker brown than the neighboring mesophyll cells. The circumstance 

 that the veins contain less nicotine than the rest of the leaf also mili- 

 tates against the view that the coloring matter is principally due to 

 the oxidation of nicotine. However, there occurs in the veins a bitter 

 principle that does not seem to oc^cur in the rest of the leaf, and perhaps 

 this may contribute to the color. 



It is easy to show that several compounds contribute to the brown 

 coloration in well-cured leaves. In the first place, much brown matter 

 is extracted by cold water. Leaves thus exhausted will yield up another 

 portion of brown matter to warm, dilute sulphuric acid, and finally 

 still another portion ^ of a different chemical behavior is extracted by a 

 warm, dilute solution of potassium hydrate. 



^The expressed juice of a fresh tobacco leaf is at finst without odor, but it gradu- 

 ally assumes that of fresh cucumbers, which later on is destroyed by putrefaction. 



'^According to Savery, the tannin of tpbacco is identical with that of coffee. There 

 exists, evidently, several kinds of phlobaphene, depending on the kind of tannin. 



•■'This latter portion is a mixture of several compounds, some colorless and pectose- 

 like, and one colored and phlobaphene-like. Twenty-five grams of fermented 

 tobacco, from Florida yielded 0.51 grams of this product. The cell membranes of the 

 tobacco thus treated exhibit under the microscope a swollen appearance. 



