78 



THE TROPICAL AGRICULTURIST. 



[August i, 1885. 



10 



30 



60 



10 



2 



0.6 

 12 



1.7 

 3.7 



12 



0.2 



3 

 20 



4 

 20.8 



black teas iu becoming yellow coloured in hot water. He 

 has found :— 



Ash ... ... ... 5J 



Tannin ... ... ... 13 



Insoluble part ... ... 60 



Water ... ... ... 10 



The same au^ilyst gives a summary of his e.xamiaation of 

 various teas, Chinese, Japanese, and Indiau,of which the fol- 

 lowing is an abstract : — 



"Water 



Soluble matters 



Tannin 



Theine 



Tea-oil 



Legumin (albumenoids) 



]\Iineral 



Other substances 



Insoluble matters 



Albumenoids ... 



Wax 



Kfisin 



Cellulose 



J&inerai 



Others 



KEMAEKS ON THE COMPOSITION OF TEA. 



Tables of chemical composition, such as tliose of tea, 

 are generally for the most part unintelligible and therefore 

 without interest to others than the initiated ; and even 

 to the latter, I may add, they are often indefinite and 

 unsatisfactory from the contradictions, real or apparent, 

 which occur in them. A few words iu addition to those 

 of Mr. Gribblo, descriptive of the composition of tea .and 

 of the applications of our present knowledge of it, may 

 perhaps be hero acceptable. The desired effects of tea- 

 driuking are almost certainly due to the hot-drink in the 

 first place, and then to the tannin, the theine or caffeine, 

 and the fragrant oil and resin iu the tea. When, farther, 

 the entire tea is consumed, as iu the use of hikl~cha in 

 this country, tea also serves as common food. This use 

 of tea as food may almost shock those keenly sensitive 

 to the exquisite delicate flavour aud the intellectualizing 

 effects of a cup of choice tea, and it will therefore be 

 noticed first, so as to get done with it. Attention then is 

 called to the fact shown by the analysis by Eder aud other 

 cnemists, that tea, with even as much as 10 per cent of water, 

 contains &hQwt oiie-q'tarto- of it-szituf/JitofallmmcHoUh, the so- 

 called ' flesh-formers.' It is consequently of but little less 

 value tlum beans. The nitrogen mentioned in Professor 

 Kinch's analysis of Japanese tea is an important chemical 

 element of these flesh-formers, being found in them to the 

 extent of 16 per cent of their weight. Hence after de- 

 ducting some nitrogen for theine, we can calculate from the 

 remainder the amount of these albumenoids. S'tiyorfaij 3-4 

 per cent.— Mr. Kinch's analysis III. — indicating in the 

 presence of 2 per ceut of theine about 2.3 per ceut albumen- 

 oids, is the usual quantity in tea cured for the foreign 

 market. The much larger quuitities of nitrogen in teas I. 

 and II., cured by the .Japanese method, are interesting and 

 need chemical investigation. Now to notice the water or 

 mohturc mentioned as present in tea. When the tea comes 

 hot from the firing operation it is without any water and, 

 if at once packed in really air-tight cases, will remain so. 

 Even by some exposure, as on keepiug in common tin- 

 canisters, it may remain a long time witli only 2-4 per 

 cent moisture al)sorbed, as my own analyses show. But 

 analyses of tea in Europe have been published, giving as 

 much as lli-17 per cent of water ; and 10 per cent is re- 

 garded there as the normal content. Thus, it will be 

 seen that every nine pounds of tea put up in Japan or 

 China, will on retailing in the United States or Europe, 

 run to ten pounds. The tea containing this water remains 

 dry to the touch. Another point of interest attaching to 

 this water, is that in its absence, the spores of vtnut and 

 mould are inactive, while they at once find a congenial 

 seat of growth when they fall in with tea containing a 

 tolerable quantity of moisture, especially when the tea 

 has been liglitly fired as by the Japanese method only. 

 With regard to the //i('(j;e, and rotdttlc oil and ri'.s'i«,it is 

 certainly of interest to note that while these are very 

 active physiological agents, aud undoubtedly give to tea 

 much of its esteemed qualities, the quantities of these 



constituents— of the theine at least— have not been found 

 to be at all in any direct relation to the recognized value 

 or appreciation of the tea. Theine is also found in 

 coffee, and as far as the possession of this sub- 

 stance is measured it may be said that one ounco 

 of tea is equal to at least two ounces and a half 

 of coffee. Two per cent is the usual proportion of 

 theine in tea. Ten-od doe.? not exist in the fresh leaves 

 of tea, but is developed by a ajiecies of fermentation 

 after they are gathered. The re^'ii appears to be the 

 substiince into which the oil changes by time. When 

 this change is complete the tea has lost its aroma. 



Tannin, so-called because it is that which when it 

 occurs in oak-bark serves to tan skiws in leather-making, 

 is found to be a useful and pleasant component of tonic 

 and refreshing draughts. It is to it that the roughness 

 of the taste of tea is due. Many persons prefer to remove 

 much of this roughness by the addition of milk, the 

 albumenoids of which render the tannin insoluble and there- 

 fore tasteless. On the other hand, a pinch of soda, or of wood 

 ashes in the water brings more of it aud other matters out 

 of the leaf, as most housekeepers have learned by experience, 

 but only at the cost of the more delicate flavour of the 

 tea. The amount of tannin is sutticiently constant in tea 

 to be trusted by the chemist, when taken with other • 

 points, iu detecting that form of sijurious tea consisting 

 of spent or once used leaves rolled and dried again for 

 sale. Tannin from other sources is sometimes added to 

 poor tea to give it a fictitious strength, an addition which 

 also occupies the chemist's atte:ition. -Japanese tea yields 

 about 13 percenter one-eirjlitli nf ,i. ircic/ht oi tannin, a 

 quantity a little higher than that of Chinese tea. Firing 

 and fermentation seem to destroy tannin, so that in 

 black teas less tannin is found than in green. In the 

 analysis of Indian tea, taken by Mr. Gribble from the 

 Indian Tea, Gazette, it can be nothing else than a mistake 

 to have made the tannin so much more than a quarter 

 of the weight of the tea. Indian tea is, however, a 

 little richer iu tannin than Japanese tea, and would be 

 more so if the cultivation of Thea Assamica had not 

 largely or entirely been replaced by that of T. Hi/brida. 

 Indeed an extract of coarse Indian tea is prepared as a 

 substitute for catechu. 



The wax mentioned in Eder's analysis comes from the 

 surface of the fresh leaves, where in a delicately thin layer 

 it protects the living leaves from undue loss of moisture. 

 The bruised leaf withers in consequence of the breaking 

 of this coating. Of the fat mentioned iu the anal) sis 

 taken from the Indian Gfzttte, I know nothing. The 

 sur/ar metitioned is not common sugar; is in very small 

 quantity only, aud does not exist ready formed in the 

 fresh leaf. 



The ash or mineral part of tea remains to be noticed. 

 Hitherto the use of the fertilizers has been but little 

 practised with tea. Experiments in India do not appear 

 to have had very promising results, although the effects 

 of the use of these agents have been quite evident upon 

 the crops of leaves got. Now any exp^^riments iu this 

 direction can only be properly carried out under the 

 guidance of a knowledge of the composition of the ash 

 of tea. This ash has been repeatedly analysed, but in 

 the present state of the matter, it would be probably of 

 little use to reproduce the published results here. The 

 ash of tea is slightly under 6 per cent of tlie te.i, of 

 which a little more than half is soluble in water when 

 in the state of ash. In the tea itself less than a third 

 of the mineral matter is soluble in its infusion, the rest 

 remaining iu the exhausted leaves, as will be seen on 

 looking at Eder's general analysis. In determining the 

 degree of adulteration of tea, the chemist depends largely 

 upon these facts. 



This ends the account of the constituents of tea. But 

 a word should he said as to the usi- of the hot infusion, 

 namely, that Europeans seem to be largely indebted to 

 the Chinese and Japanese for a knowledge of the pleasure, 

 if not advantage, of hot beverages, as much in hot weather 

 as in co'd. 



It will be seen that tea leaves properly dressed and 

 eaten form a nutritious diet ! As to the colouring of 

 teas, Dr. Diver shows that the quantity of colouring 

 matter used by foreiga merchauta cau do little, if any 

 harm, 



