Aui 



1886,] 



THE 'TROPICAL AGRj(C0Lt0RISf;, 



9; 



THE CHEMISTRY OF TEA. 



Although we agree with Mr. Barber that Dr. Watt 

 was mistaken in supposing that damage to tea-lead 

 ■ was due to badly prepared tea, the real cause being 

 almost invariably badly seasoned wood acting 

 chemically on the lead, we yet feel that the 

 researches of the professional chemist may largely 

 aid the operations of the professional tea-maker. 

 For instance, in regard to the process which is 

 generally known as " fermentation," a term for 

 which " oxygenation " has been latterly substituted, 

 an authority we have consulted refuses to recognize 

 as true fermentation any process promoted by the 

 oxygen of the air. The question, therefore, arises, 

 is the change which rolled lea-leaves undergo, in 

 the process of which they are as much as possible 

 fiuardcd from direct contact tcitJi the outer air, true 

 fermentation, or merely oxygenation, whatever the 

 latter nray involve? Tea-leaves contain a normal 

 proportion of sugar and starch, which are not in 

 themselves ferments, but they are, of course, liable 

 to the action of ferments and fermenting agents, 

 whether associated with them in the crushed leaves 

 or extraneous. But, if the generally-received doctrine 

 be true, that fermentation depends on the presence 

 of the spore of an organism which feeds on and 

 so ferments the sugar, then the professional chemist, 

 who must be a good microscopist, ought to be 

 able to tell us, what specific organism the spore 

 represents, — whether the yeast plant, Torula cerevi»<.r, 

 or some other. That question decided, the chemist 

 might be able to observe and instruct the tea-maker 

 to observe and decide, by a careful use of the 

 microscope, the thermometer and other appliances 

 and tests, the signs in the life-history of the spore, 

 temperature raised by fermentation and other 

 indications, the period when fermentations may 

 best be arrested by the leaf being subjected to the 

 action of lire. Oxygenation seems a more pleasant 

 term to use than fermentation, but, as even those 

 planters who prefer the former term admit tliat 

 oxygenation, if allowed to proceed too far, will end 

 in putrefaction, we feel inclined to believe that 

 the saccharine matter in tea-leaves is acted on by 

 some vegetable germ derived from the atmosphere 

 in the same way that thu yeast spore acts on the 

 sugar in malt used for transformation into beer. 

 It is highly probable that the spore is that of a 

 different organism, however, the action of wliich 

 as a fermenting agent may be slower and less 

 violent as a heat-producer ? Such are some of the 

 points on which tea-makers might benefit by the 

 examination and advice of professional chemists. 

 But, as we have said, every tea maker is really 

 a chemist in degree, and what seems wanted is 

 that chemical knowledge in the case of the tea 

 maker should in certain directions be amplified 

 and extended. A peripatetic chemist, therefore 

 going the rounds of the various tea factories, pursuing 

 researches into the chemistry of tea with the aid 

 of practical men, and giving those practical men 

 the benefit of theory founded on science, shewing 

 them the reasons for processes wliich by rule of 

 thumb they have perhaps long practised, and 

 recommending improved methods as the result of 

 research, might confer great benefit on the tea 

 enterprise as well as on himself, for in this, as 

 in other cases, the labourer would be deemed worthy 

 of his hire. We. may probably be revealing un- 

 justifiable ignorance, wlien Ave ash, has the develop- 

 ment of any spores of minute organisms ever been 

 observed in tea leaves undergoing the process of 

 fermentation? Messrs. Gow, Stanton & Co. do not 

 seem to recogni?;e fermentation due to the presence 

 of vegetable spores. Their lar'juage indicates a 

 b«lief in chemical thauges effected by tiie air^ 

 13 



irrespective of flie germs which inhabited it. We 

 quote from one of their circulars, as follows: — 



" 'Without further considering the intermediate pro- 

 cesses of rolling, &c., we come to the firing. About 

 this operation there appears to be mistaken views. 

 Tea mu.st not be calcined. This is the whole secret. 

 The leaf, when in its withered state (properly withered 

 that is), contains most delicate chemical products, to 

 be dealt with very differently from what on many 

 estates it now is. The process too prevalent is, to " fire 

 off " quickly, and such a process at the high temper- 

 atures now used really burns out its active principle. 

 Analytical experts declare that when the leaf is pro- 

 perly dried, the tannin or astringent principle remains 

 undisturbed. The aroma of the leaf is dependent on 

 the careful application of heat at a certain main- 

 tained degree of temperature. Then, too, with a very 

 high temperature the process of firing destroys the 

 gum and the theiue, leaving the .tlmost charred woody 

 product behind, which, when infused, gives such un- 

 satisfactory results, and leads to so many complaints 

 of quality. From our own personal knowledge of tea- 

 planting we venture to ask planters, when dealing with 

 'green' leaf, to keep the following facts before them, 

 viz: — Starch is universally diffused throughout the 

 vegetable economy, esjjeciiilly in leaves, that the ab- 

 sorption of oxygen from the air converts starch into 

 sugar, and that the green resinous principle of the leaf 

 diminishes in quantity while oxygen is absorbed. The 

 excellence of black tea depends upon the management 

 of the leaves in such a way that the above noted 

 chemical changes may take place." 

 But the question we should wish to see authorit- 

 atively decided by a well qualified chemist, is, — 

 Can the mere oxygen of the air absorbed by starch, 

 converting tliat starch into sugar and diminishing 

 the proportion of green resinous principle, in the 

 tea leaf, account for the changes which take place 

 in rolled leaf during the process in which the 

 colour i^asses from vivid green to bright copper? 

 Do or do not some of the teeming life germs with 

 which the atmosphere seems to be loaded, have 

 as much or even more to do with the chemical 

 change, than even the absorption of oxygen ? Can 

 oxygen indeed be absorbed by the moist, bruised 

 mass, perfectly pure and unaccom.panied by spores 

 which when they come in contact with sugar produce 

 "fermentation?" Will some expert kindly reply? 



MR. SHAND'S LECTURE ON TEA. 



Dr. Watt of India and BIr. Barber of Ceylon on 

 the Chemistry of Tea. Mr. Barber has sent us a very 

 interesting letter from which we quote as follows: — 



On Wednesday Mr. Shand read a paper on British- 

 grown teas and treated the subject in its many 

 aspects, domestic, sentimental and political. After 

 this Dr. Watt, one of the Commissioners for India, 

 spoke of his experiences in India and on tea matters 

 generally. At the end he wound up by referring to 

 bad packing and faulty manufacture, rapid drying 

 and wrong fermentation and sucli other " rot" that 

 he knew nothing of, but deemed fit to speak about, 

 in order to say that he thought chemistry and 

 science could help the tea planter to avoid certain 

 consequences and in order that he might iu short 

 teach his grandmother to suck eggs. Excuse this 

 vulgarism. I can find no better words to express 

 my disgust at treating a Lone m audience to faults 

 manifold and pernicious in their results, just 

 altera paper treating on the excyllence of Bi.tish' 

 grown teas as against foreign teas.* He said 1st, 

 that we tired off too fast, that in preparing bota- 

 nical specimens they dried slowly with blotting 



* Dr. Watt has uone good service in classifying and 

 describing the vegetable products of India, but his 

 contentior. that badly fermented tea cnrrodos the 

 lead of tea cbes's, exposed hiin to deserved ridicnlo. 



