51 



REPORT ON THE ADULTERATION OF DAIRY PRODUCTS. 

 By HERMANN (\ LYTHOOE, Associate Referee. 



The referee, with the help of Messrs. Nurenberg and Marsh, assistant analysts of 

 tin- Ma.-.-a< hu.-eii.- State board of health, has made a study of the different methods for 

 tin- preparation <>f milk serum and for the detection of calcium sucrate in cream. As 

 u result of thi> work it is apparent that the provisional method for the preparation of 

 milk serum need.- n<> modification, but the method of Baier and Neumann for the 

 detection of sucrone in milk or cream should be made provisional. The work done is 

 embodied in the two following articles. 



A COMPARISON OF METHODS FOR THE PREPARATION OP MILK SERUM. 



The samples of milk used in this investigation were all milked in the presence of an 

 inspector <>r an analy.-t i the Massachusetts State board of health and represented 

 nearly all breeds of dairy cattle, particularly the Holstein, Ayrshire, Dutch Belted, 

 and -rade Holstein cows. The methods employed were the provisional (acetic acid) 

 method, natural souring," calcium chlorid method, & and asaprol methods The 

 detail.- !' th- nit i h<>d- "t h-r than the provisional methods are as follows: 



Natural souring method. Allow the samples to sour spontaneously and filter off the 



serum. 



( 'nlrni in chloral nn (fun/. Place 90 cc of milk in a flask, add 0.75 cc of calcium chlorid 



solution -|> -r I I '.. > when diluted 1:10 this solution reads 26 on the immersion 



reirartnmeter at I, ' ike thoroughly, close the flask with a cork carrying a 



as a retlux condenser, place i'n a boiling water bath for twenty minutes, 



o>.. I t<> _'() J , mix tin- o.nden-ed water and serum without shaking, and filter. 



Aw\>rnl tntthod. The precipitating solution is made by dissolving 30 grams of 

 illi/.t d itric acid in 1 liter of water. If the refraction 



of this .-.lution i- i i the scale of the immersion refractometer at 20, add 



water or < itri< a .id to make it so. Mix equal volumes of the above solution and the 

 milk, .-hake \\cll. ami til 1 - 



In the accompan\ in- table are the results of the refraction of the milk serum pre- 

 1 from milk samples of known purity when two or more methods were applied 

 to the Mime sample of milk. The asaprol method is by far the easiest of manipulation. 

 It -ives the clearest serum in the least time and shows the lowest refraction with the 

 least variation. I nfortunately pure asaprol is very difficult to obtain, and, owing to 

 the fat that it decomposes readily, it is not an easy matter to prepare different solu- 

 tions that will give identical sera with the same sample of milk. The calcium chlorid 

 method is the most difficult of manipulation and is liable to give a cloudy serum rather 

 troublesome to read, but the results are lower than those obtained by the acetic acid 

 method and not so variable. The natural souring method is too slow for ordinary use, 

 but is valuable in the hot weather if the milk is nearly sour when it reaches the analyst. 

 Four years' experience with the provisional method has shown it to be reliable, easy 

 of manipulation, and to give concordant results. 



Matthew and Muller, Zts. offentl. Chem., 1903, 10: 173. 



kerman. Zt- I'nii-rsurh. Xahr. Genussm., 1907, 13: 180. 

 I'.aier and Neumann. Zts. Untersuch. Nahr. Genussm., 1907, 18: 369. 



