COLORING MATTER. 193 



Thickening agents for cream. Gelatin is added to cream for 

 the purpose of increasing viscosity and giving the appearance 

 of greater richness than is really the case. For detection, see 

 Leach (5). 



Sucrate of lime (viscogen) is sometimes used in order to 

 make pasteurized cream whip. It is a harmless adulteration 

 and permissible when the product is so labeled. 



Heated milk. Storch has devised a test that will indicate 

 whether milk, cream or other dairy products have been heated 

 to 178 F. (80C.). It is carried out as follows : A teaspoon- 

 ful of milk is poured into a test tube and one drop of a weak 

 solution of peroxide of hydrogen (2%) and two drops of a 2% 

 solution of paraphenyldiamin are added. The mixture is then 

 shaken. If a dark violet color appears at once, the milk has 

 not been heated, or at any rate, not above 175 F. 



Coloring matter. The chief object of adding coloring matter 

 to milk is for the purpose of concealing either skimming or 

 watering. Two classes of compounds are used, vegetable and 

 coal-tar colors. Some of the latter are harmless, as naphthol 

 yellow S or Orange I, as declared in the U. S. Department of 

 Agriculture, Food Inspection Decision 76. Only a very small 

 amount of coloring matter is used and the effect is generally 

 harmless ; but such additions are in violation of the law in 

 that they tend to mislead and deceive the consumer. The 

 detection of added coloring matter in milk cannot very well be 

 undertaken away from a chemical laboratory. Full and com- 

 plete directions for the testing of milk for the presence of 

 added coloring matter will be found in Bulletin No. 107 (7). 



If there is any suspicion that a milk has been adulterated 

 with coloring matter, it should be allowed to stand undis- 

 turbed for several hours in a glass vessel. If then the sample 

 exhibits different zones of color, it may safely be said that the 

 milk contains no added coloring matter. The different colors 

 should be the yellow of the cream, which overlies the stratum 

 of a mixture of milk and cream of a lighter color, under which 

 is the bluish layer of skimmed milk. If, on the other hand, 

 the color is more or less uniform throughout the sample, it 

 should be further examined for confirmation. 



