NATURE 



21 



TEA IN JAPAN. 

 Researches on the Manufacture of Various Kinds of Tea. 



Bulletin of the Imperial College of Agriculture and 



Dendrology. By Y. Kozai, Assistant in the Agricultural 



Chemical Laboratory. (Tokio, 1890.) 

 '\7 KOZAI is a Japanese chemist who performed his 

 •i • researches under the control of Dr. Kellner, the 

 Director of the Chemical Laboratory at Tokio. His paper 

 includesthe chemical constitution of tea, the effect of tea on 

 mankind, the principal methods of manufacture employed 

 in Japan, and the methods of preparing tea for consump- 

 tion. These subjects are all treated mainly from the point 

 of view of the analytic chemist. The author appears 

 fairly well acquainted with what the German chemists 

 have done in the matter of tea. 



We need not abstract much of his account of the con- 

 stitution and properties of tea, as it is largely taken from 

 European sources. " The chief action of tea, after it has 

 got into the blood, is to excite the nervous system ; it thus 

 harmonizes the mind, drives out drowsiness, and awakens 

 thought, stops hunger, and cures repletion, refreshes the 

 body, and prevents head-ache" — and (it might be added) 

 if taken too strong keeps you awake half the night. As 

 to its constitution, tea contains (besides the common 

 plant-constituents) theine, a volatile oil, and tannin. 

 Theine is a rank poison, in toxic doses causing convul- 

 sions and paralysis, in lethal doses death ; but in small 

 quantities is (like strychnine) a delicate tonic. Of the 

 volatile oil, Y. Kozai can affirm little beyond its well- 

 known exciting action upon the organs of taste and smell ; 

 nor is it easy to follow it analytically through the pro- 

 cesses of manufacture ; the hot steaming employed (at 

 near boiling temperature) in the green-tea manufacture does 

 not appear to diminish the volatile oil sensibly, though 

 Y. Kozai intimates that preparing green tea by boiling 

 does dissipate the aroma. As to the properties of tannin, 

 it is an astringent remarkable for its strong affinity for the 

 albuminoids ; hence, if taken in excess, it may, by pre- 

 cipitating the ferments of the digestive fluids, cause 

 indigestion. 



The account of the chief Japanese methods of manu- 

 facture is of more interest and instruction to the European 

 planter. 



We may premise that there are two (main) kinds of 

 tea, viz. black and green. In the manufacture of black 

 tea there are four essential processes, viz. (i) withering ; 

 (2) rolling, (3) fermenting, (4) drying. In the manufacture 

 of green tea, the fermenting is omitted, and in Japan (for 

 some kinds of green) the rolling also. 



For the manufacture of black tea there is no real 

 difference between the Japanese method and that prac- 

 tised by English planters in Bengal. The fresh picked 

 leaf {i.e. tips of the young shoots) must be first withered, 

 or the petioles and leaves break under the rolling ; the 

 exposure of an hour or two in strong sun withers the leaf 

 sufficiently ; if there is no sun, the leaf must be withered 

 by the aid of fire-heat. The rolling is done, even in 

 Japan, by the aid usually of a box, and in Bengal often 

 NO. 1075, VOL. 42] 



by steam-power (and very roughly). The juices are thus 

 expressed, and the leaf given a "nice" twist, i.e. a twist 

 pleasing to the fancy of the tea purchaser. What perhaps 

 renders rolling so essential in the manufacture of black 

 tea (for it is not esssential in the manufacture of green), 

 is that it masses the leaf in a state conducing without 

 delay to fermentation. Neither Y. Kozai nor the best 

 Bengal authorities like to lose the juices more than can 

 be helped. He also hazards the view that, by rolling, 

 the juice is expressed from the cellular tissues of the 

 leaves and impregnated upon their surface ; thus is pro- 

 duced fine aroma, and the leaves are more easily infused. 

 Fermentation is the most important point in the manu- 

 facture of black tea, and by it {fide Y. Kozai) the leaves 

 lose their raw smell, and the tea acquires its fine flavour. 

 The fermentation is really only carried a very little way : 

 Y. Kozai says it should be allowed, in a temperature 

 of 104° F., to proceed only for about an hour. He 

 thinks the process is a true fermentation, because if per- 

 mitted to run too far the tea acquires an acid taste. 

 He thinks it probable that the ferment is caused by a 

 living organism, but he adduces very slight ground for 

 this opinion ; and it has, in fact, been questioned whether 

 there is any true fermentation in the process at all. But 

 the English tea-makers are agreed with the Japanese in 

 the importance of stopping the fermentation exactly at 

 the proper point by drying the tea, which is usually done 

 by placing it first in the sun and turning it over till it is 

 fairly dry, and then thoroughly drying it by fire-heat. 



The result of all the Bengal experience is that the 

 black tea is at least as good when these four processes 

 are done simply and rapidly, as when much labour and 

 time are expended in complicating them. In the early 

 days of tea manufacture by Anglo-Indians, great pains 

 were taken to imitate with tedious minuteness the careful 

 hand-processes (and repetitions of portions of the pro- 

 cesses) as practised in China ; but all planters now follow 

 rapid short cuts to the finished tea. 



The manufacture of green tea is nothing more than 

 drying the leaf ; it is so little practised in British India 

 as to be of no commercial interest there, but Y. Kozai 

 describes in detail three kinds of green tea manufactured 

 in Japan. 



(i) Japanese (not China) green tea. In this, the leaf is 

 steamed in order to remove the raw flavour ; it is then 

 rolled and fire-dried, the two last processes being usually 

 done together. 



(2) Chi?iese green tea. In this, the leaf is roasted (while 

 stirred with a stick) in an iron pan over a fire, then rolled 

 a little, then roasted again ; these processes being re- 

 peated even six or eight times, and the tea is then finally 

 dried off. 



(3) Flat tea, the highest class tea of all. For this tea, 

 the shrubs are usually kept shaded for three weeks before 

 picking, so that the leaf is partly etiolated. The choicest 

 leaves are selected before the manufacture is commenced. 

 They are steamed, but never rolled ; nor, indeed, touched 

 by hand at all, but carefully turned by the aid of a bamboo 

 stick. After sufficient steaming they are simply dried. 



The author finds by analysis that there is 30 per cent, 

 more theine in etiolated leaves than in the leaves of the 

 same plants grown in the light. He tried many experi- 

 ments to test the chemical effect of the manufacturing 



G 



