[ 454 ] 



If Rs. 125 are realized per acre, and 6 mnds. obtained as 

 the outturn per acre, tea can be worked with profit. The fixed 

 charge of Rs.65 per acre in European gardens is rather heavy. 



712. The principal pests of tea plantations are the 

 Mosquito blight and the Red Spider. Against the former 

 pruning and hoeing and burning have been found useful, also 

 spraying of Kerosine emulsion and against the latter dusting 

 of Sulphur. For a full account of tea-blights students are 

 referred to Indian Museum Notes, Vol. III. No. 4. 



713. The chemical changes that take place during manu* 

 facture of tea are numerous; one of the most important being 

 an increase in the amount of essential oil, to which the flavour 

 of tea is so largely due. A certain amount of volatile -fatty 

 acids are also developed from the splitting up of a portion 

 of the albuminoid matter in the leaf, and the sap developes an 

 acid reaction. Some of these on isolation have a sweet nutty 

 flavour and aroma, to which the peculiar smell of properly 

 oxidized leaf is due. If the process of oxidation is prolonged 

 for many hours, the acidity of the sap rapidly increases and 

 the leaf becomes sour and rancid, acids similar to those in 

 rancid butter being developed. These can be got rid of to a 

 certain extent by firing, by exposing the leaf to a high tempe- 

 rature for a lengthened period, but only at the expense of 

 the volatile oil which is dissipated with them. The astrin- 

 gency due to tannin is also greatly reduced during this process 

 of oxidation, the tannin being partly oxidized into an insolu- 

 ble brown substance known as Phlobaphine and partly 

 combining with some of the albuminoid matter and which 

 gives the leaves a tough, leathery and elastic character easily 

 noticeable on handling. Part of the tannin is also converted 

 into glucose and gallic acid, the former of which tends to give 

 a sweetish flavour to the tea and the latter is less astringent 

 than tannin, and it has not the power of combining with 

 albuminoid matter. The albuminoid matter of the leaf is also 

 partly coagulated by the acidity developed during the oxida- 



