Edible Products. 



534 



[December, 1908. 



nection between the seed and its testa, 

 it must be mentioned that by the death 

 of the seed, caused by the elevation of 

 temperature of the fermentation to 40° 

 to 45° C, some contraction cakes place 

 and the seed recedes somewhat from its 

 walls. Later on, in the manufacture 

 of cacao from the fermented and dried 

 beans, they are roasted and some con- 

 traction of the seed is caused. The 

 testa having lost its hygroscopic water 

 by the heat, now can be easily separated 

 especially while still warm and brittle. 



An important change also due to the 

 fermentation process is the production 

 of a fine brown colour. The effect of 

 the fermentation in this direction is, 

 however, not a direct, as supposed by 

 many, but an indirect one, and may be 

 secured by simply drying the bean. 

 Sun-dried beans are uniformly deep 

 brown. When the fresh seed is cut, 

 the surface thus opened will turn from 

 the original violet to a deep brown 

 colour within a short time, while boiled 

 seed thus treated will not show any 

 change of color, even after many hours' 

 exposure to the air. This is in full 

 analogy with similar phenomena observ- 

 ed very frequently with plants, and 

 is due to the presence of oxidases or 

 oxidyzing enzymes. When cells arekilled 

 by being cut open or in any other way 

 that will not injure the oxidases, these 

 will, upon the death of the protoplasm 

 in which they were stored up, be 

 Jiberated and commence at once their 

 activity, easily recognized by the early 

 appearance of a brown, black, or red 

 colour. These colours are generally due 

 to the oxidation of various kinds of 

 tannins originally present in the juice or 

 cell sap.* If, however, the death of the 

 protoplasm is produced by strong acids 

 or boiling temperature,! the oxidases 

 will also be killed and no colour change 

 Avill be noticed, as the tannins and 

 other readily oxidizable matters in the 

 juices cannot easily take up the atmo- 

 spheric oxygen without the assistance 

 of oxidases. 



A further control experiment was 

 made in which the pulped cacao (seed 

 with testa and attached slime layer) 

 was boiled for about twenty minutes 

 with dilute sulphuric acid of 2 per cent. 

 The slimy tissue contracted, and to- 

 gether with the swollen testa was easily 

 separated from the seed. These seeds 

 showed a pure red coloration on the 

 outside, while the interior was violet, 



*Such a case is observed in the curing of 

 tobacco, whereby a fine brown colour is produced. 



f The kdling temperature for oxidases is 20° 

 to 30° C. higher than that for protoplasm or 

 living matter. 



and no trace of brown colour appeared 

 even after may hours' exposure to the 

 air, since the oxidizing enzyme (oxidase) 

 has been killed, together with the living 

 matter (the protoplasm of cells). 



The seeds commence to die when the 

 entire fruit is kept for several days at 

 40° to 45° 0., and the browning can 

 be observed progressing from the surface 

 of the seed toward the interior. By 

 becoming over ripe, the soft interior 

 strata of the fruit shell, as well as the 

 slime tissue around the seeds contract 

 more or less, and a hollow space is formed 

 between the fruit shell and the seeds 

 with their adhering slime tissue- Air 

 diffuses into this space, and the reason 

 for the brown colour produced by oxida- 

 tion within the firuit becomes apparent. 

 During the fermentation process the 

 browning does not often go farther than 

 this, and the interior of the seed often 

 continues to show the original violet 

 colouration. It is then that the subse- 

 quent drying process, which admits air 

 abundantly by diffusion through the 

 testa, completely finishes the browning 

 process, Some further darkening can 

 take place during the roasting process 

 when powdered cacao and chocolate are 

 made from the fermented beans. 



The colour change of the cacao seed is 

 no doubt similar to the colour change in 

 the preparation of black tea, for which 

 it has been positively proved that an 

 oxidising enzyme acting on a specific 

 tanuin is the real cause of the blacken- 

 ing of the leaves. When the oxidising 

 enzyme of the tea leaves is killed by 

 steam, the leaves retain theirgreen colour 

 and never turn black (green tea). 



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 pick- 

 ing and are deprived of sunlight (death 

 by starvation). Indeed, black tea con- 

 tains less tannin than green tea. In 

 order to increase the black colouration 

 the leaves are rolled, which brings their 

 juice to the surface, and the access of air 

 accelerates the blackening process. 



A case in which tannin is changed by 

 partial oxidation for the sake of remov- 

 ing the astringent taste is observed in 

 the curing of the fruit of certain varieties 

 of persimmon (kaki) in Japan. By the 

 curing process, which consists in keeping 

 the fruits in vapour of alcohol or in 

 subjecting them to slow desiccation in 

 the sun, the tannin is changed, in contact 

 with an oxidising enzyme and oxygen, to 

 a brown, tasteless substance. The fruit 

 thus acquires an agreeable taste. 



(To be continued). 



