TEST FOR WATERED MILK 



The following quick and simple test is recommended to dis- 

 tinguish between raw and boiled milk! 



REAGENT 



Methylene blue (alcoholic) 5 cc. 



Formaldehyde (40 per cent.) 5 cc. 



Water (distilled) 190 cc. 



Add i cc. of this reagent to 20 cc. of the milk and heat for 10 

 min. at 4o-45 C. Raw milk is decolorized 

 while boiled milk retains the blue coloration. 

 This test should in all cases be checked by the 

 microscopical examination. Boiling the milk 

 causes the fat globules to unite and adhere more 

 or less, a characteristic which is also noticeable 

 in pasteurized milk. The flavor and odor of 

 boiled milk is in itself quite characteristic. 



Knapp recommends the following test for 

 determining the addition of water to milk. 10 

 cc. of the suspected milk are run into a test-tube 

 and curdled by adding one drop of rennet and 

 placing the tube in the water bath for about 2 

 min. at a temperature of 35-4o C. The 

 whole is then poured upon a very fine wire sieve 

 and the liquid allowed to drain off into a tube 

 graduate, pressing the curd with a glass rod so 

 as to remove the liquid as completely as possible. 

 The amount of liquid remaining in the curd 

 is fairly constant in the tests and therefore 

 practically negligible for comparative purposes. 

 If the amount of liquid drained off exceecjs 8 coccus aureus i week 



old. (MacNeal.) 



cc., water has been added. This test should be 

 checked by the chemical butter fat tests and also by the microscop- 

 ical method for determining the fat content, as already explained. 

 Among the micro-organisms which cause the coagulation of 

 milk and which are often found in sour milk, particularly in old sour 



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