Edible Products. 



36 



[January, 1909, 



In testing for a second oxidizing 

 enzym, the peroxidase, the tissue of the 

 seed, crushed with a little water, was 

 heated for five minutes to 75° C, and one 

 portion of this liquid was filtered, the 

 other not. The test with guaiacum 

 tincture yielded no blue reaction in 

 either liquid, proving that the oxidase 

 was killed, while on addition of a little 

 paroxid of hydrogen the unfiiltered juice 

 gave an intense blue reaction and the 

 filtered juice showed only a trace. This 

 difference proves that the peroxidase, 

 like the oxidase, was present, but 

 retained as an insoluble compound — an 

 exceptional case. 



Reactions with guaiacol were also 

 tried. This substance produced no 

 coloration when applied by itself, but 

 in conjunction with hydrogen peroxid a 

 red colour turning to brown was soon 

 produced in both the hard as well as 

 the soft layer of the fruit shell. Later, 

 in the testa and the seed in general, as 

 well as in the slime tissue covering the 

 testa, only a weak, reddish coloration 

 was produced. This peroxidase reaction 

 agrees also with that just mentioned, 

 in so far as the slime tissue gave only an 

 exceptionally weak reaction compared 

 with all other parts of the fruit. The 

 slime tissue of the coffee fruit is also 

 poorer in oxidase and peroxidase than 

 the other tissues. 



The further generation of the charac- 

 teristic aroma of cacao is of great im- 

 portance. Is this process due to the 

 action of an oxidizing enzym or to that 

 of a hydrolizing enzym, and does the 

 fermentation influence the generation 

 of aroma only indirectly by the develop- 

 ment of heat or directly by furnishing 

 some compound? Or, is the roasting of 

 the fermented cacao beans alone res- 

 ponsible for the aroma ? The investiga- 

 tions thus far made do not solve this 

 problem satisfactorily. It may be men- 

 tioned, however, that Hart agrees with 

 Chittenden, who declared that aftei a 

 certain stage of the fermentation "the 

 cotyledons are found separated and the 

 vinous liquor of the pulp, which passes 

 through the membranous covering, 

 occupies this space as well as the cavities 

 between the convolutions. * * * This 

 it is which has so marked a physiological 

 influence and affects its flavour, the bean 

 being, as may be said, 'stewed in its own 

 juice. ' " 



According to the laws of osmosis some 

 acetic acid and some alcohol from the 

 fermenting liquor will doubtless enter 

 through the testa and come in contact 

 with the cotyledons, which thereby may 

 be killed, if the temperature of the 

 fermenting mass has not already accom- 



plished this. The reaction of the cotyle- 

 dons after drying the fermented beans 

 is acid, but whether this is wholly due 

 to the entering acetic acid may be doubt- 

 ful, since the reaction is weakly acid in 

 the fresh state. A stronger acid reaction 

 is shown by the slime tissue. 



The expression " stewed in its own 

 juice" used by Chittenden can hardly 

 be admitted, since the juice of the pulp, 

 after being entirely decomposed by 

 yeast and bacteria, is certainly not the 

 "own juice "of the cotyledons. Still, 

 that author attributes to it the gener- 

 ation of the flavour. 



The opinion of J. B. Harrison that the 

 decrease of tannin during the fermenta- 

 tion process stands in relation to the 

 development of aroma is certainly far 

 from the mark, as tannin cannot 

 produce ethereal oils by an oxidation or 

 fermenting process. Only colour and 

 taste stand in this relation to the tannin 

 content. 



Several experiments were made by 

 the writer with an aqueous solution of 

 1 to 4 per cent, acetic acid containing 

 from 3 to 5 per cent, of alcohol in order 

 to imitate the composition of the 

 fermenting pulp juice. After twenty to 

 thirty hours' digestion of pulped cacao 

 at 40° to 45*C. it was observed that the 

 pulp had died and shrunk to skinny 

 masses, parti} separating in small 

 pieces, but mostly still firmly adhering 

 to the testa. It appears that for bring- 

 ing about an easy separation of the dead 

 pulp from the testa a bacterial enzym is 

 necessary, as in the case of coffee 

 fermentation. It was further observed 

 that the amount of acetic acid, which 

 entered by osmosis through the testa to 

 the coytyledons, was not sufficient 'to 

 kill the oxidizing enzym, since the 

 freshly cut surface of these seeds rapidly 

 turned brown on exposure to the air. 

 On the other hand, it was observel that 

 when the freshly cut surface of the 

 seeds so treated was moistened with 4 

 per cent, acetic acid no further change 

 by oxidatiou took place. In this case 

 the oxidizing enzym was killed. 



It is stated by Hart that "of late years 

 there has been a large amount of inquiry 

 for cacao which is but slightly fermented 

 or not fermented at all. " This renders 

 it very probable that the decomposed 

 juice of the slime tissue is not required 

 for the generation of the aroma as was 

 supposed. Indeed, the true aroma of 

 cacao is faint before roasting the fer- 

 mented beans. The case is, therefore, 

 similar to that of coffee, and is different 

 from that of tea. With tea the aroma 

 is the result of the action of a hydrolizing 

 enzym, yielding the volatile tea oil, as 

 was shown by Katayama. 



