March, 1909.] 



219 



Edible Products. 



In order to understand the ferment- 

 ation process, it must be remembered 

 that on the surface of all sweet fruits 

 are a great many yeast cells and bacteria. 

 When by the pulping the sweet juice is 

 forced out and spread all over the 

 separated skin, and over the pulped 

 coffee, it is not surprising that these 

 organisms develop rapidly. The sweet 

 juice not only contains sugar but 

 also some nitrogenous and mineral 

 matters required for the development of 

 organisms. 



An examination of the skin with a 

 high magnifying power several hours 

 after pulping shows numerous cells of 

 Saccharomyces, which in form resemble 

 chiefly Saccharomyces ellipsoideus and 

 sometimes also S. apicidatus. 



Numerous bacteria are also present. 

 Alcoholic fermentation can soon be de- 

 tected by the vinous odour, and the fact 

 that the fermentation produces heat ex- 

 plains why the temperature of such a 

 heap of pulp rises considerably after a 

 time. A heap of nearly 30 centimeters 

 in height showed after sixteen hours a 

 temperature of 41°0. at an air temper- 

 ature of 20°C. Later, acetic acid isformed 

 and the red colour of the skin changed to 

 a brownish one. 



When the pulped coffee, on the other 

 hand, is examined, a few yeast cells and 

 bacteria are noticed on the slimy stratum 

 after one hour, while after sixteen hours 

 an immense increase has taken place, and 

 not oaly is considerable alcohol formed 

 by the yeast cells but also acetic acid by 

 certain bacteria. Mycoderma and the 

 mycelium of fungi are occasionally seen. 

 Litmus is reddened intensely and the 

 odour of acetic acid readily discernible. 

 At the same time another volatile pro- 

 duct is formed in small quantity, which 

 modifies somewhat the acid odour. 



The alcoholic fermentation of the sugar 

 adhering to the slimy stratum, as well 

 as the further oxidation of the alcohol to 

 acetic acid, and finally the respiration 

 process carried on with considerable in- 

 tensity by all these organisms, cause a 

 rise of temperature, depending upon the 

 depth of the stratum and the temperature 

 of the surrounding air. The heaps of 

 pulped coffee are gene rally 1 to 2 feet high. 

 In such heaps the temperature was found 

 after fifteen to sixteen hours to range 

 from 34° to 42° C. at an air temperature of 

 25° to 29° C. 



The alcoholic and acetic fermentations 

 proceeding in the heaps of pulped coffee 

 are, however, not the most essential 

 phenomena ; the most important point is 

 that the slimy stratum is separated from 



the parchment envelope. It is by no 

 means dissolved, but merely loses its firm 

 adhesion and is left loosely spread upon 

 the parchment coffee so that it can easily 

 be washed away by a current of water 

 and the parchment coffee dried. 



Neither the acetic acid nor the enzyme 

 already present in the slime causes the 

 separation of the slime lnyer, as tests 

 have shown. 



Freshly pulped coffee was kept in 

 dilute acetic acid (about 1 per cent.) at 85° 

 to 40° C, and another portion in some 

 water containing a few drops of ether to 

 prevent bacterial growth. In both eases 

 the slimy layer was found still firmly at- 

 tached to the parchment after twenty 

 hours. This leaves no other inference 

 but that a peculiar enzyme dissolving the 

 adhesive substance (a carbohydrate?) be- 

 tween the parchment and the slimy 

 stratum was furnished by the bacterial 

 growth, or, what is less probable, by the 

 yeast cells. 



The "fermentation" should not take 

 longer in Porto Rico than fifteen tu 

 twenty hours, while in some sections 

 of Central America, as Guatemala, it 

 must be carried on for two days. 



Undue prolongation of the ferment- 

 ation must be avoided, as otherwise a 

 brown colouration of the parchment and 

 of the seeds is produced and the seeds 

 further acquire a disagreeable odour — 

 two circumstances which render the pro- 

 duct unfit for the market. 



After the fermentation and washing 

 the parchment of the coffee is readily 

 dried, either on cement floors exposed 

 to sun and air. or better in rotating 

 cylinders through which warmair passes. 

 At a certain degree of dryness the parch- 

 ment becomes brittle and breaks easily 

 in the milling process, which thus re- 

 moves .the parchment envelope and silver 

 skin from the seeds. In fact, the milling 

 must be done while the parchment is 

 still warm. 



This milling is in many eases done in 

 Loudon, and not in the country where 

 the coffee is produced. Better preser- 

 vation of shape and colour of the bean 

 has been observed, when the latter is 

 protected for a time by the parchment 

 envelope. The cost of transportation is 

 in this case a little higher, but it does 

 not come into consideration, as from $2 

 to $3 more has been realized per hundred- 

 weight for coffee thus treated than for 

 that cured in Central America. 



In reviewing the so-called ferment- 

 ation of coffee, the conclusion is inevit- 

 able that alcoholic; and acetic ferment- 



