8o The Fermentation of Cacao 



the leaf) the midrib and (on compressing a 

 handful of leaves) the connecting stalks no 

 longer break. The leaves are then rolled by 

 a mechanical contrivance which causes an 

 alternating, heavy and light pressure to be 

 brought to bear on them in such a way that 

 during the application of the heavy pressure 

 the sap of the leaf is forced out and spread 

 over the surface, to be absorbed by the leaf 

 again when the pressure is relieved. The 

 main object of rolling is to rupture the cells 

 of the leaf, or at least to render them more 

 permeable to air. The time occupied to do 

 this varies between one and one and a half hours 

 according to the nature of the leaf. Owing 

 to the rolling, the leaves become considerably 

 heated and simultaneously the amount of acid 

 and soluble astringent substances is increased. 

 After rolling, the resultant massed leaves are 

 passed through a sieve-like contrivance which 

 loosens them, and then exposed to oxidation 

 in thinner or thicker layers, varying according 

 to the temperature conditions. Oxidation then 

 proceeds rapidly, as, owing to the rolling, 

 access of air to the interior of the leaves is 

 facilitated ; the process takes from two to eight 

 hours, according to the temperature and nature 

 of the leaves. Owing to the oxidation of the 

 astringent substances, the green colour of the 

 leaves turns yellow or copper-coloured, but 

 before this stage is reached, the oxidation should 

 be stopped, otherwise the tea becomes over- 



