Changes in Certain Water-soluble Nitrogenous Constituents of Burley Tobacco during Curing.

Introduction An investigation of the chemical changes that take place in tobacco during curing is in progress at the Kentucky Agricultural Experiment Station. Attempts are being made to determine what the normal changes are and how they are influenced by such variables as temperature and relative humidity, which have been shown to influence the final quality of tobacco. A study of this type adds to the knowledge of leaf metabolism during starvation and drying. Knowledge of the chemistry of curing may lead to methods of producing high quality tobacco which have not been found empirically. This paper reports the results of experiments on the changes that occur in certain water-soluble, nitrogenous constituents of the tobacco leaf during curing and of the effect of relative humidity upon these changes in chemical composition. Relative humidity was used as the variable rather than temperature because the work of JEFFREY (3) showed that differences in relative humidity cause larger differences in quality of the tobacco than do differences in temperature, within the limits encountered in practical Burley tobacco curing. Chemical investigations of the tobacco plant have been made in many regions where tobacco is an important cash crop but very little of this work has dealt with the chemistry of curing. The most complete studies of the chemical changes that occur during the curing of tobacco were made by VICKERY (10, 13) and his associates at the Connecticut Agricultural Experiment Station. Primed leaves of a Connecticut shade-grown variety of cigar tobacco were cured in a curing shed and analyses were made of the leaves at different stages of curing. The analyses included insoluble nitrogen, several fractions of the soluble nitrogen, ash, carbohydrates, and ether extract. In 1914 GARNER (2), of the Bureau of Plant Industry, reported on some chemical studies of tobacco curing. Both primed and stalk-cured leaves of several Connecticut cigar varieties were analyzed before and after curing. Analyses included several carbohydrate fractions, several organic acid fractions, several soluble nitrogen fractions, ash, and protein nitrogen. Ash and dry matter were expressed as grams per 100 leaves. The other analyses were expressed as percentage of dry weight.