STUDIES ON THE CURING OP LEAF TOBACCO. 39 



drying. It is seen that initial partial drying materially hastens the 

 disappearance of starch, but for the interval of time covered by the 

 experiments there was no important difference in the rate of hydrol- 

 ysis of protein. The less-marked differences as regards starch in 

 the 1912 experiment were doubtless due to the fact that there was 

 much less difference in water content (about 8 per cent) between the 

 two samples as a result of the partial drying than was the case with 

 the 1911 samples. In view of these results it appears that the 

 thorough wilting of the tobacco leaves at the beginning of the curing 

 process promotes good curing. 



SUMMARY. 



Curing is essentially a life process, as is shown by the fact that 

 killing the protoplasm at excessively low or high temperatures or by 

 means of poisons, such as chloroform, effectually prevents normal 

 curing. It follows, also, that imperfect curing can not be fully cor- 

 rected in the subsequent process of fermentation, which is not 

 dependent on the living protoplasm. 



Experiments covering a period of four years have shown that in 

 the case of cigar-wrapper-leaf types the average loss in weight of dry 

 matter in curing the picked leaves is 12 to 15 per cent, while in curing 

 the leaves on the stalk the loss in dry weight is approximately twice 

 as great. In other words, a cigar-wrapper leaf picked from the stalk 

 will weigh after curing approximately 14 to 18 per cent more than 

 would the same leaf when cured on the stalk. 



In the curing of the export and manufacturing types and of cigar- 

 filler types, which are harvested in a riper or more mature condi- 

 tion, the loss in weight of dry matter is greater than in the case of 

 cigar-wrapper leaf, frequently amounting to 35 to 40 per cent, even 

 when the leaves are picked from the stalk in harvesting. With most 

 of the export and manufacturing types the stalks are split in har- 

 vesting, and under these conditions the loss in dry matter in curing 

 is considerably less than when the stalk is simply severed near the 

 base in harvesting. 



The chemical changes which take place in curing can only be 

 properly brought out by presenting all results on the basis of the 

 uncured leaf. It has been shown that in thorough air curing all 

 starch and reducing sugars disappear and there is a decrease of 

 pentosans and malic acid, while there is an increase in citric acid 

 and the cellulose content remains unchanged. There is a large 

 decrease in protein, in some cases amounting to 60 per cent of the 

 total, and a considerable decrease in nicotine and total nitrogen. 

 Appreciable quantities of ammonia are formed in the process. 



In the curing of picked leaves the chemical changes appear to be 

 due almost wholly to respiration, while in curing the leaves on the 

 stalk the phenomenon of translocation from the leaf into the stalk 



