154 FLAVORING AND BEVERACJE PLANTS 



quantity it often has upon the nervous sj'stem a marked 

 effect, which may be injurious or beneficial according to 

 circumstances. The coffee "bean" contains about 0.5-2% 

 of caffeine, dried tea leaves about 1-3%. Theobromine, of 

 which there is about 1.5% in the cacao seed, is found to be 

 scarcely soluble in the fluids of the body, and thus exerts 

 little if any effect. 



The most active constituent of each of the three beverage 

 plants we are considering is the aromatic substance to which 

 its peculiar flavor is due. Li black tea there is about .5%, 

 and in green tea al)Out 1% of a volatile oil which is mainly 

 developed during the curing or preparation of the leaves for 

 market. The commercial value of a tea depends mainly 

 upon the flavor imparted Ijy its volatile oil. This flavor is 

 carefully tested by experts who are known as "tea-tasters," 

 although curiously enough tliey smell rather than taste the 

 samples sul)mitted to them. Even so, the effc^ct of the vola- 

 tile oil upon the nervous system is so powerful as to cause 

 giddiness and headache if the "ta.sting" be continued more 

 than a few hours a day; and it is said that the most vigorous 

 cannot pursue the work for many j-ears without suffering 

 serious consequences. The peculiar aroma of coffee is not 

 found in the raw "bean" but is developed during the process 

 of roasting; that of cacao arises during the process of fermen- 

 tation which the seeds undergo liefore they are ready for 

 market. In coffee the aromatic constituent is hardly as 

 powerful as in tea, while in cacao it is so mild that vanilla and 

 various spices are added as flavoring to make chocolate. 



Finally, mention must be made of an astringent constituent 

 belonging to the class of substances known as tannine. This 

 forms about 10%, of dry tea leaves. It is similar to the sub- 

 stance extracted from bark for tanning leather. Black ink is 

 commonly made bj' combining tannin with a substance con- 

 taining iron. When taken with food in considerable quanti- 

 ties this astringent interferes with digestion. Prolonged boil- 

 ing extracts it in lai'ge amount from tea leaves; conse(iu(>ntly 

 tea so jircjiared is most injurious. Steeping hir a short time, 

 on the contrary, removes l)ut little of th(> tannin, while it ex- 

 tracts [)rac1 icall\' all of the exhilarating and aromatic constit- 



