No. e. DEPARTMENT OF AGRICULTURE. 669 



The starches which I have most commouly met iii adulterated 

 chocolates are those of ludiaii corn and wheat or rye. As all of 

 these starches differ greatly in size and manner of polarization from 

 the starch belonging to the cocoa bean, the detectioii of the adultera- 

 tion is an easy matter. The percentage of starch found by chemical 

 analysis in husked and roasted cocoa beans averages about eight per 

 cent. 



As would be expected from Uie delinitioo previously given of choco- 

 late, we find the same percentage of starch in pure chocolate as in 

 the husked aod roasted beans. Consequently if a chocolate is found 

 by microscopic examination to contain added starch and the amount 

 of starch in the sample be then estimated, all the starch found above 

 eight per cent, may reasonably be regarded as due to adulteration. 

 Tlie substances used for adulteration in many cases, however, are not 

 pure starch. For example, if wheat starch is found in a sample of 

 chocolate, the substance used to adulterate the chocolate is prob- 

 ably wheat flour. If the starch of wheat flour is estimated by the 

 hydrochloric acid process, the yield is found to be about seventy per 

 cent. Consequently if the excess of starch found in a sample of 

 chocolate adulterated with wheat flour is found to be ten per cent., 

 this number would represent only seventy per cent, of the actual 

 adulteration, or the amount of wheat fln\ir would be between fourteen 

 and fifteen per cent. 



In order to detect cocoa husks in cholocate, the sample is best pre- 

 pared for microscopic examination as follows: Boil a portion of the 

 sample from which the fat has been previously extracted in dilute 

 liydrochloric acid (about one and one-fourth of acid) for ten minutes, 

 allow the powder to settle, decant oft" the liquid, wash several times 

 by decantation, then boil for about five minutes in one and one-fourth 

 [ler cent, caustic soda solution. After cooling, filter and wash. The 

 residue is then bleached by chlorinated soda and again washed. By 

 this treatment the dark colored and opaque tissue of the cocoa husks 

 are rendered so nearly colorless and tviiiispnrr'nt that their micro- 

 scopic anatomy is very easily seen. 



If a piece of cocoa husk be soaked in water, three coats or layers 

 become plainly visible to the unaided eye. An outer and an inner 

 coat, each composed of rather firm opaque tissues separated by a 

 rather thick nearly colorless mucilagenous substance forming the 

 middle layer. Ramifying through the inner coat which is quite thick 

 and dense are numerous fibro-vascular bundles which can be seen 

 by the unaided eye as fine parallel ribs apparently running from end 

 to end of the husk. When examined by the microscope this inner 

 coat is found to be quite complex and to contain several layers of 

 cells. One of these layers is composed of oblong, thick walled cells 

 which form a distinguishing microscopic characteristic of the cocoa 



