January, 1909.] 



35 



Edible Products. 



THE FERMENTATION OP OACAO, 



By Oscar Lobw, Physiologist. 

 (Concluded from page SSJj,,) 



Since a moderate brown colour is also 

 produced in white "nibs," free of cacao 

 red, it follows that the brown colouration 

 is not due exclusively to a change of 

 cacao red. If the production of the 

 colour is due to an incomplete oxidation 

 ot the tannin, then there will be less 

 tannin found in the cured cacao than in 

 the fresh cacao. This agrees, indeed, 

 with some analytical determinations or 

 J. B. Harrison, published by Hart. The 

 fat content is assumed not to change 

 during the curing process, and this is in 

 all probability the case. The data com- 

 piled under this condition are as follows 

 for Oalabaciilo cacao :— 



Analyses op Oalabaciilo 



Constituents. 

 Fat 



Tannin 



Oacao red ... 



Theobromin 



Caffein 



Starch 



Glucose 



Hemicelluloses 



Woody fibre 



Protein 



Amido compounds 



Fresh. 



Per ct. 

 29-25 

 5-00 

 2'95 

 1-35 

 ■11 

 3-76 

 0-99 

 511 

 3-03 

 6 69 



Cacao. 

 Cured. 

 Per ct. 

 29-25 

 3'61 

 1-39 



1- 00 

 •03 



3'22 

 0-60 



3- 74 



2- 78 



4- 42 

 2-06 



A part of the changes brought about by 

 curing is probably due to the action of 

 the living cells in the seed, before they 

 are killed by the rising temperature. 

 This would account for the decrease of 

 starch, glucose, and hemicellaloses, which 

 may be consumed by the respiration 

 process, but the other changes are due to 

 several enzyms. A proteolytic enzym 

 brings on the decrease of protein and the 

 corresponding increase of amido-com- 

 pounds, while oxidizing enzyms, generally 

 liberated from the protoplasm upon 

 its death, cause the decrease of tannin 

 and cacao red and their change to other 

 compounds. The most conspicuous 

 changes are, therefore, only possible after 

 the death of the protoplasm which is a 

 desirable factor. Hence, it is a mistaken 

 idea of Zipperer that the changes are due 

 to a germination process of seeds. He has 

 even attributed the rise of temperature 

 of the fermenting pulp cacao to this 

 process, considering it analogous to the 

 behaviour of barley on the malting floor. 

 This error can only be explained by the 

 fact that he has never witnessed the 

 fermentations of cacao or coffee ; for 

 germination changes are not in the least 

 apparent, 



Another result is the change of flavour. 

 In the fresh state the seeds have a raw 

 bitter, and astringent flavour, while after 

 fermentation and drying the bitter and 

 disagreeable taste has entirely disap- 

 peared. This change is doubtless due in 

 a certain measure to the decrease of 

 tannin ; that is, to its change by oxida- 

 tion to a brown substance, as in the case 

 of the persimmon fruits, mentioned 

 above.* The flavour of the fermented 

 beans is still far different from that of 

 the prepared cacao product, which is 

 produced by roasting the fermenting 

 beans ; hence a part of the taste must be 

 due to changes caused by the heat of the 

 roasting process. 



The presence of oxidizing enzyms in 

 the seeds of cacao can be proved by the 

 usual reaction. Upon moistening a 

 freshly cut section of cacao seed with 

 tincture of guaiacum resin, just after 

 taking the seed from the ripe fruit, a 

 blue colour is rapidly produced, first 

 and most intensely in the chalaza of 

 the embryo and gradually spreading 

 over the entire seed tissue ; also, the 

 placenta shows soon an intense blue 

 colour. When a cross section through 

 the whole fruit is moistened with 

 guaiacum tincture, the chalaza of the 

 embryo and the interior soft stratum of 

 the fruit shell become rapidly and 

 intensely blue, then follow in order the 

 colouration of the convulsions of the 

 cotyledons, of the seed and the tissue of 

 the hard outer shell. Finally, the whole 

 surface of the section of the seed and 

 exposed tissue of the testa become blue ; 

 but the slime tissue or pulp around the 

 testa remains perfectly colourless, 

 presenting a most striking contrast. 



If the tissue of the seed is crushed 

 with some water in a mortar, the filtered 

 liquid will show no blue colouration on 

 addition of guaiacum tincture and shak- 

 ing with air, while the unaltered liquid 

 will become blue very soon. This shows 

 an exceptional case, namely, that the 

 oxidase (laccase) is present in an inso- 

 luble state and perhaps held in combi- 

 nation with an insoluble protein. t 

 Upon standing the blue colour, obtained 

 Avith the unfiltered liquid, will gradu- 

 ally disappear, except on the surface, 

 buo on adding a few more drops of the 

 reagent and shaking, the intense blue 

 colour reappears. This phenomenon is 

 due to the presence of a reducing com- 

 pound in the juice. 



• The opinion of Harrison mentioned above 

 that the decrease of the astringent taste is 

 due to a hydrolysis is erroneous and would be 

 without analogy. 



fThis recalls the existence of a soluble and 

 insoluble form of catalase, 



