THE CHEMISTRY OF COFFEE 179 



increased temperature required. The following are experimental 

 results : 



Losses for ordinary coffee 19-3% total loss. 



" of original fat 9-7% 



" " " caffeine 21.1% 



Losses for sugar-glazed coffee i5-3% total loss. 



of original fat 18.3% 



caffeine 44-3% 



Roasting is the most important operation in the preparation of 

 coffee, and should be carried on in a closed vessel in which the 

 beans are constantly in motion and under uniform temperature. For 

 the best results, only beans of one size should be roasted at a time. 

 The beans emit smoke, turn brown, and commence to sweat, which 

 shows that the essential oil is being separated, and the beans become 

 glossy. 



By just the proper degree of roasting, the volatile oil is produced 

 at the expense of some other constituents. Jaeckle found in 1898 

 that caifeine is volatilized slightly and certain other products are 

 formed, such as acetone, furfural, ammonia, trimethylamine, formic 

 and acetic acids. Moriari and Scoccianti, however, reported in 1895 

 that if the beans are heated to 26o°C., no trimethylamine is formed, 

 but he detected appreciable quantities of pyridine and its homologues. 

 The fat is somewhat decomposed, which results in increased amounts 

 of free fatty acids. The sugar-content of the beans becomes caramel- 

 ized, and the caffetannic acids lose one-half of their weight. The 

 volatile oily substance is termed "calfeone" or "caffeol," and has 

 been held to be the chief factor responsible for the aroma of coifee. 

 Bernheimer has suggested for caffeol the formula C8H10O2 or 

 C6H4(OH) .CH2.OCH. The chemistry of the formation of this 

 substance is not well understood. It is the product of torrefication 

 and the influence of heat on the other constituents which produces 

 the materials for its composition. Its identity, however, has re- 

 cently been disputed ; and several authors have detected pyridine. 

 Moreover, Erdmann has found that the aroma of coffee was pro- 

 duced w^hen caffeine, sucrose, and caffetannic acids are heated to- 

 gether, and that the absence of any one results in the non-existence 

 of the aroma. The dietetic property of coifee is due to caifeine, 

 CgHioNiOa, and is not affected by torrefication beyond a slight loss 



