220 Milk Inspection. 



of rennet producing species- of bacteria, which are peptonizing 

 bacteria, the presence of which is undesirable in drinking milk. 

 Not infrequently the best milk produces imperfect curds. 



Milk from diseased animals curdles more poorly, with the 

 formation of an abnormal curd. 



Still less important than the fermentation test is the rennet 

 fermentation test which is used in cheese factories, where the 

 milk, before being placed in the incubator is mixed with a solution 

 of rennet. The resulting curd should be elongated and worm- 

 shaped, contain few gas bubbles, and should not look twisted or 

 pressed flat or swollen. 



The rennet inhibitory test recently recommended by Schern 

 accomplishes other purposes than the rennet fermentation test. It 

 tests the power of resistance of the milk against the effect of the 

 rennet. For the test the following are necessary : 



1. A number of test tubes. 



2. Measuring pipettes of 10 c. c. capacity with y 2 c - c - gradua- 

 tion and 1 c. c. pipettes divided in tenths and hundredths of 

 c. c. graduations. 



3. A water bath or an incubator with a number of perforated 

 racks. 



4. An icebox. 



5. 0.85% solution of common salt. 



6. Solutions of rennet, the values of which are known and 

 which remain constant (standard solutions of a known titer). 



In the performance of the test it is desired to ascertain : 



1. Whether the titer of the solution of rennet still persists 

 with sound milk. 



2. Whether the milk to be tested by means of the rennet 

 titer does not curdle, or how much more rennet is necessary to 

 make the milk curdle. 



The samples are placed for 1 hour in the icebox, and then for 

 2 hours in the incubator, whereupon through pouring, a test is 

 made as to which dilution of rennet has curdled the milk or 

 whether the milk curdles at all up to the limit of titration. 



The test is not applicable to market milk, but only for fresh 

 individual samples or samples of milk from individual quarters. 



Milk which utilizes considerably more of the rennet solution 

 than the amount which corresponds with its titer is suspected of 

 not being normal. 



The test is too laborious for practical control work and does 

 not offer any advantages for the recognition of inflammation of 

 the udder over the microscopical examination of the centrifugal 

 sediment. 



The methods by which the milk is examined for the content of 

 complement or amboceptor have the same shortcomings. They 

 are of no importance in control work. 



The test for complement is as follows: 



