46 The Fermentation of Cacao 



preparation of black tea, in which it has been 

 positively proved 1 that an oxidizing enzyme 

 acting on a specific tannin is the real cause of 

 the blackening of the leaves. When the oxi- 

 dizing enzyme of the tea leaves is killed by 

 steam, the leaves retain their green colour and 

 never turn black, thus giving us the green tea 

 of commerce. 2 



Tea leaves contain 7 per cent, tannin and 

 over, and the production of a black colour from 

 this tannin commences as soon as the leaves 

 die, which takes place when they are kept in 

 heaps after picking, and are deprived of sun- 

 light (death by starvation). Indeed, black tea 

 contains less tannin than green tea. In order 



o 



to increase the black colouration, the leaves are 

 rolled, which brings their juice to the surface, 



1 K. Aso. "Bui. Col. Agr. " Tokyo, Imp. Univ., 4 

 (1900-1902), p. 255. It may be of interest to readers to 

 remember that, from 1893 to J 897, Dr. Loew occupied 

 the important position of Professor of Agricultural 

 Chemistry at the College of Agriculture, Tokyo Univer- 

 sity. See Tropical Life, February, 1910, p. 32. H. H. S. 



2 Even to-day we are told that whilst great strides 

 have been made since the formation of the Scientific 

 Department, it is doubtful, according to the Dooars 

 correspondent of a contemporary of the Indian Planters 

 Gazette, if there is any agricultural pursuit about which 

 less is known by the men occupied in it than tea. 

 Especially is this the case in the tea house. .We succeed 

 in turning out quite passable tea, and are at times vain 

 enough to think that we have made as good tea as 

 it is possible to produce from the leaf at our disposal. 

 But the present methods may be revolutionized at any 

 time by new discoveries. Take one branch of manu- 



