338 CLEAN MILK 



Stocking and Mason* have made elaborate experiments to deter- 

 mine the best way to cleanse and sterilize the rubber tubing and teat 

 cups of milking machines. They found that bacteria multiply rapidly 

 in ten -per cent, brine' solution, which has been commonly used. 

 Continuous sterilization of rubber by boiling water or steam for a 

 proper period to sterilize is destructive to -the rubber parts. The 



•' method finally adopted was to first rinse the tubing and teat cups 



1 with-clean water after each milking. This is done by connecting the 

 machine to the vacuum system near a sink, and, by plunging the teat 



'cupsin the sink,. clean water is drawn through the teat cups and 

 tubing into the milk pails. The next step consists in soaking the 

 teat cups arid rubber tubing in a 3^ per cent, solution of formalin in 

 water* between milkings. Just before milking the rubber tubing and 

 teat cups are again thoroughly rinsed in clean, boiled water. The 



' -miik ", pail' and pulsator are sterilized by steam in a sterilizer or by 



' boiling in' water. 



By" the -above -method the bacterial content of milk Withdrawn 

 by machine was about the same as that Obtained by hand under 

 cleanly conditions in the same stable. In order to secure the best 

 results a thin layer of absorbent cotton is placed in the air- relief of the 

 teat cup connector and of the head of the machine to filter the 

 bacteria from the stable air. At these two points the air rushes in at 

 each pulsation of the machine to relieve the vacuum. After doing 

 this the bacteria in the- machine-drawn milk (averaging 1,578 bacteria 

 per c. c.) were reduced to about one-third of those in the milk drawn 

 by hand (averaging "4,'56o' bacteria per c. c.),under like conditions. 

 The milk from the milking- machine kept twice as long as the milk 

 withdrawn by hand, .*'. <?., milk at 72 degrees soured after 38 hours 

 when withdrawn by hand ; machine-drawn milk kept sweet for 

 72 hours. 



The only objection to the use of formalin in keeping the parts of 

 the milking machine clean is the possibility • of milk being con- ' 

 taminated by a trace of it. The presence of formalin in milk is 

 illegal and would provelobe the greatest misfortune to one supplying 

 a high grade of milk, as suggesting the possibility of intentional 



* Storrs Agricul. Exper. Sta. Bull. 47, May, 1907. 



