1901.] H. H. Mann— ne Enzymes of the Tea Leaf, 155 



longer break, but are sufficiently pliable to roll up. At this stage it is 

 rolled, a process whose effect is to break the cells of the leaf, allow the 

 sap to spread itself over the surface , and so come in contact with air 

 during the process of fermentation. This latter merely consists in 

 exposing, for a time varying from two to six hours, the rolled leaf in thin 

 layers in as cool and airy a room as possible. Marked changes here 

 take place ; the green leaf takes on a brown coppery colour and acquires 

 an aroma totally different from that of fresh leaf. "When sufficiently 

 fermented, — which is judged at present entirely by appearance and 

 smell, — the whole mass of tea is dried usually by a powerful current of 

 hot air, sorted and put on the market. 



It is evident that the changes important from our point of view 

 principally takes place during withering and fermentation. Withering 

 has usually been considered to be little else than a process of partial 

 drying without the loss of pliability which would take place were the 

 operation conducted at a high temperature, and the idea that profound 

 chemical changes may take place has hardly been mooted. On the 

 other hand, the speculations as to the nature and cause of the fermenta- 

 tion process have been legion. In the early days it was usually consi- 

 dered to be merely incipient putrefaction, and this idea was supported 

 by the fact that a slightly longer exposure than that given leads to an 

 intensification of the brown colour, to the development of increased acidity 

 and ultimately to putrefactive decomposition. 



Prior to the experiments of Mr. Bamber,* the statements made 

 rested on no experimental basis. His work however has revolutionised 

 the ideas on the subject. He maintained (1) that very few orga. 

 nisms were present, and the time was too limited for their development 

 in quantity, and that hence the process could not be caused by bac- 

 teria, (2) that the fermentation will not take place in absence of oxygen, 

 even if the oxygen was replaced by carbon dioxide, (3) that a large 

 quantity of air is required, (4) that after heating the leaf with dry 

 steam for a few minutes the fermentation proceeded normally. Hence he 

 maintained that the so-calld fermentation process was not a fermen- 

 tation at all, but was due merely to the direct chemical action of the 

 atmospheric oxygen on the constituents of the juice exposed in thin layers, 

 and he hence substituted the term " oxidation " for " fermentation " in 

 naming the process. 



In this position the question remained, except for mere speculative 

 opinions,t until the beginning of 1900, when Mr. Bamber returned 

 to the question, and to a certain extent revised his former opinion. He 



* Chemistry and Agriculture of Tea, 1893. 



t See, for instance, D. Crole, Journal of the Society of Arts. 



