. 
29 
At the end of the curing process the amount of free acid for a given 
surface was therefore reduced considerably.' A portion of the acid 
may have passed into the stalk, another portion may have been com- 
pletely oxidized, and another may have been neutralized by ammonia 
formed in the destructive action of oxidizing enzyms on nitrogenous 
compounds. In the subsequent sweating process the liberation of 
ammonia is more energetic, and neutralizes the rest of the acid. The 
decrease of acidity in the curing process is of practical importance, 
since the following sweating process will set in with sufficient energy 
only when the reaction is nearly neutral. The practice of the tobacco 
manufacturers in Florida of applying a spray of ammonium carbonate 
solution when the ‘“‘hea»ys will not heat up well” is therefore in accorda- 
ance with the scientific inference. 
BEHAVIOR OF THE OXIDIZING ENZYMS IN THE CURING PROCESS. 
In a normally conducted curing process, whether curing single leaves 
or curing on Stalk, the oxidase and peroxidase are well preserved. This 
is not the case under conditions unfavorable to a normal curing. The 
oxidase especially loses its active character more or less. Flue curing 
seems just as injurious’ as prolonged moist weather. The acidity in 
the leaves is, according to the writer’s observation, generally too weak 
to cause injury; but the occasional entrance of too much sunlight into 
the barn may diminish the oxidase in the exposed leaves. Reynelds 
Green, and Brown and Morris have shown that enzyms, as, for example, 
diastase, are injured by exposure to direct sunlight, while with regard 
to the action of water it has been shown by Laborde that a gradual 
destruction of oenoxidase takes place within twelve days by self-oxida- 
tion when it is dissolved in water and exposed to air. There can 
hardly be any doubt that much water retained for a certain time in 
the curing leaves of the barn will favor self-oxidation of the tobacco 
oxidase. This is also shown by the following test. 
A large upper leaf was placed in a covered glass cylinder contain- 
ing some water, to insure ap atmosphere saturated with water vapor. 
After being kept in darkness for a week at from 22° to 28° C., compari- 
son with a normal leaf showed less oxidase in the parenchyma of the 
leaves so treated than in that of equally old fresh leaves of the same 
plant, while with the veins the difference was not so marked. On the 
other hand, no decided decrease of peroxidase could be noticed. 
‘In the pith and bark no decrease of acidity, but, on the contrary, a slight inerease 
was observed during the first two weeks of curing. Further it may be mentioned 
that the acidity seems to decrease more slowly when the leaves are single cured than 
-when cured on stalk. Only one test was made, however, in regard to this. 
2F lue curing is mainly used in the curing of the bright yellow tobacco of Vir- 
ginia, Tennessee, and North and South Carolina. The temperature reached thereby— 
71-79° C. (160-175° F.)—is detrimental to the oxidase. Such tobacco, however, is not 
subjected to sweating. 
