768 



BOTANY AND PHARMACOGNOSY. 



adjoining walls of three individual grains. Most of the aggre- 

 gates, however, swell into rounded masses (35 /x in diameter) 

 resembling wheat starch grains, and have a clearly defined wall 

 and nearly homogenous, hyaline contents. They may be distin- 

 guished from wheat starch by the use of dilute alkali or acid 

 solutions, which cause an immediate breaking down of the 

 masses without the successive changes in structure noticed on 

 similar treatment of wheat starch grains (Fig. 96). 



O 





 CD 



O 



O 





O 



0G 









c^ 



Fig. 308. Cacao starch: A, starch grains of commercial cacao powder, or chocolate, 

 after removal of the oil by means of ether; B, altered starch grains of cacao produced by 

 making sections or scrapings of the raw cacao bean, removing the oil with ether, mounting 

 on a slide in water and heating at a temperature of 70 C, for a few seconds; a, b, c, d, 

 successive stages in the alteration of 2-, 3-, and 4-compound grains, the various masses 

 showing resemblance in size and form to the single grains of corn, wheat and even potato 

 starch as seen in some of the swollen masses (S). 



Plain chocolate or cocoa mass is obtained by grinding the 

 broken cotyledons (cocoa nibs) in a mill and separating the pasty 

 mass, which is molded into forms that usually weigh a pound. 

 Cocoa is the plain chocolate from which a part of the fat (cocoa 

 butter) has been removed, the resulting product being then pow- 

 dered. Sweet chocolate is plain chocolate to which sugar and 

 various flavoring substances are added. Milk chocolate is a 

 sweet chocolate to which " milk powder " is added. 



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