Condensed Milk and Milk Powder 227 



DETECTION OF ARTIFICIAL COLORING 1 



LEACH'S METHOD 



"Warm about 150 c.c. of milk in a casserole over the flame and 

 add about 5 c.c. of acetic acid, after which slowly continue the 

 heating nearly to the boiling point while stirring. Gather the curd, 

 when possible, into one mass by the stirring rod, and pour off the 

 whey. If the curd breaks up into small flakes separate from the 

 whey by straining through a sieve or colander. Press the curd free 

 from adhering liquid, transfer to a small flask, and macerate for 

 several hours (preferably over night) in about 50 c.c. of ether, the 

 flask being tightly corked and shaken at intervals. 



1. "DETECTION OF ANNATTO (IN THE ETHER EXTRACT) 



"Decant the ether extract as obtained above into an evaporating 

 dish, place on the water bath, and evaporate the ether. Make the 

 fatty residue alkaline with sodium hydroxid, and pour upon a very 

 small wet filter while still warm. After the solution has passed 

 through, wash the fat 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 solution, which, in presence of annatto, produces 

 a characteristic pink on the orange-colored paper. 



2. "DETECTION- OF ANILIN ORANGE (IN THE CURD) 



"The curd of an uncolored milk is perfectly white after com- 

 plete extraction with ether, as is also that of a milk colored with 

 annatto. 



"If the extracted fat-free curd is distinctly dyed an orange or 

 yellowish color, anilin orange is indicated. To confirm the presence 

 of this color, treat a lump of the fat-free curd in a test tube with 

 a little strong hydrochloric acid. If the curd immediately turns pink, 

 the presence of anilin orange is assured. 



1 United States Department of Agriculture, Bureau of Chemistry, Bulletin No. 107 



