178 COFFEE 



Tatlock and Thompson state that tannin is not found in roasted 

 coffee and that the lead precipitate contains the coloring matter. 

 They report 4.5% of tannin as precipitable by gelatin in raw coffee. 



In conclusion, the following table presents a general mean compila- 

 tion of the chemical analysis of various investigators who used coffee- 

 beans of Coffea arabica L. as their base : 



Composition Per Cent in Per Cent in 



Raw Beans Roasted Beans 



Ash . 3 to 4 4 to 5 



Albumin 10 to 1 1 1 1 to 13 



Caffeine i-j- i 



Caffetannic Acid 8 to 10 4 to 5 



Cellulose (crude fibre and non-nitroge- 

 nous matter) 38 48 



Dextrin I i 



Fat and Oil 11 to 13 13 to 14 



Moisture 10 to 1 1 1 



Nitrogenous Extract and Coloring Matter 4 to 7 12 to 14 



Sugar 9 to 10 ^ 



Effect of Roasting the Coffee-Bean 



Roasting and pulverizing coffee-beans induces the changes to which 

 the Havor and aroma are largely due. The toughness of the bean 

 is destroyed, which facilitates the subsequent grinding. If not 

 previously removed, the testa or so-called "silver skin" separates 

 during the roasting-process, and is known as flights or fibre, and 

 should be removed before grinding. The process should be carried 

 on at a temperature of 200°-250° C. Torrefication causes the beans 

 to swell and lose from 12 to 20% of their weight, of which 8% 

 is removable water. If they are roasted to a yellowish-brown color, 

 about 12.5% of their weight is lost, the product is difficult to grind, 

 and the flavor is not well developed. If they are roasted to a chest- 

 nut-brown color, 18% is lost, and the beans are brittle and possess 

 a pleasing aroma and flavor. If roasted until black, even although 

 not entirely carbonized, the beans lose 23% of their weight, and 

 the product has a nauseating and empyreumatic flavor. In general, 

 112 lbs. of raw berries yield 98 lbs. of roasted coffee or a loss of 

 12.5%. According to Hilger and Juckenack, if the coffee is glazed 

 with sugar, the losses on roastmg are much higher, owing to the 



