222 MILK 



from the filter with a stream of water and dry the paper. If, after 

 drying, the paper is colored orange, the presence of annatto is 

 indicated. Confirm by applying a drop of stannous chlorid solu- 

 tion, which in presence of annatto produces a characteristic pink 

 on the orange-colored paper. 



Annatto can also be detected in milk if 10 c.c. are mixed with 

 ether and then shaken. After the ether has separated it becomes 

 yellow if annatto was present. - 



Detection of Anilin Orange (Leach). If the extracted fat- 

 free curd (see above) is distinctly dyed an orange or yellowish 

 color, anilin orange is indicated. To confirm the presence of this 

 color treat a lump of fat-free curd in a test-tube with a little 

 strong hydrochloric acid. If the curd turns pink immediately, 

 the presence of anilin orange is assured. 



Anilin dyes in milk can be detected by mixing 10 c.c. of milk 

 with 10 c.c. of strong hydrochloric acid. A pink color appears in 

 their presence. 



Detection of Caramel (Leach). If the fat-free curd is colored 

 dull brown, caramel is to be suspected. As in the test for anilin 

 orange, shake a lump of the curd with strong hydrochloric acid in 

 a test-tube and heat gently. In the presence of caramel, the acid 

 solution will gradually turn a deep blue, as will also the white 

 fat-free curd of an uncolored milk, while the curd itself will not 

 change color. It is only when this blue coloration of the acid 

 occurs in connection with a brown colored curd, which itself does 

 not change color, that the presence of caramel is to be suspected, 

 as distinguished from the pink coloration produced at once under 

 similar conditions by anilin orange. 



The following summary of the scheme, for color analysis is 

 given by Leach: 



" Curdle 150 c.c. of milk in a casserole with heat and acetic acid. Gather 

 the curd in one mass. Pour off whey, or strain, if curd is finely divided. 

 Macerate curd with ether in corked flask. Pour off ether. 



Ether Extract. 



Evaporate off ether, treat 

 residue with NaOH, and 

 pour on wetted filter. After 

 the solution has passed 

 through, wash off fat and 

 dry filter, which, if colored 

 orange, indicates presence 

 of annatto. (Confirm by 

 SnCl 2 .) 



Extracted Curd. 



1. If colorless indicates presence of no 

 foreign color other than in ether extract. 



2. If orange or brownish indicates presence 

 of anilin orange or caramel. Shake curd in 

 test-tube with concentrated HC1. 



If solution gradually 

 turns blue, indicative of 

 caramel. (Confirm by 

 testing for caramel in 

 whey of original milk.) 



If orange curd im- 

 mediately turns pink, 

 indicative of anilin 

 orange." 



