21 6 Milk Inspection. 



From the uniformly fine or coarse particles of dirt in milk, or 

 from the presence of cow hair in large amounts and larger par- 

 ticles of dirt, it may be determined whether the dirty milk has 

 been strained after the milking. 



The filtration methods in which disks of cotton are used as 

 filters have an advantage in that they indicate more distinctly the 

 actual content of dirt than the sedimentation methods, where a 

 considerable proportion of the dirt is drawn up into the cream 

 during the separation. The author uses an apparatus in which a 

 disk of cotton is held in a simple plate-shaped filter, over the vessel 

 into which the milk is to be poured. The cotton disk is pressed 

 into the filter by a glass cylinder, as is the case with the apparatus 

 of Fliegel and Bernstein. At the present time such dirt testing 

 apparatus may be purchased from nearly all dealers. For the 

 household and for small amounts of milk certain filters are recom- 

 mended like those in which the filling funnel represents a bottom- 

 less bottle, to the mouth of which a ring and a wire strainer con- 

 taining a disk of cotton are attached, by means of a wire fastener. 



Henkel's control filter is also based on the principle of filtra- 

 tion through cotton by which an angle-shaped segment of the filter- 

 ing disk remains free from dirt in order to control the purity of 

 the milk. The same result is attained with other methods where 

 the border of the filtering disk remains free from dirt. 



At the places of official examination of milk distinction is 

 made between slight, moderate, strong, very strong, and exception- 

 ally strong pollution, and the milk accordingly is judged as either 

 clean or spoiled or even injurious to health. 



Market milk may be tested at receiving stations either by 

 drawing up samples from the bottom of the cans with the aid of 

 long pipettes, or, as is customary in Munich, by pouring the milk 

 from the original can into another vessel. The residue of the milk 

 in the first case is taken as a sediment sample, while an average 

 sample is taken from the mixed milk of the second container in 

 order to make a quantitative estimation. 



Trommsdorff's test is splendidly adapted to the detection of 

 finely divided particles of dirt, the heavy particles being collected 

 in a capillary tube. 



The methylene blue reductase test gives very good information 

 relative to bacterial multiplication. A solution of methylene blue 

 in water, serves as a reagent, consisting of 195 parts H 2 and 5 

 parts saturated alcoholic methylene blue solution. The test is con- 

 ducted by placing 20 c. c. of milk and 1 c. c. of methylene blue 

 solution in a reagent glass at 40 C. and the time is determined in 

 which the sky blue mixture becomes completely white. Milk which 

 becomes white in less than 3 hours is already old. The age, how- 

 ever, does not refer to the hours since its production, but means that 

 the milk has "aged." Milk which is obtained in a dirty condition, 



