Contamination of Milk. 29 



one of which had been cleaned in the ordinary way, while 

 the other was sterilized by steaming. Before milking, the 

 iidder of animal was thoroughly cleaned, and special pre- 

 cautions taken to avoid raising of dust; the fore milk 

 was also rejected. Milk was then drawn directly into 

 these two cans and bacterial determinations made: 



Number of bacteria per cc. in steamed pail, 165. 



Number of bacteria per cc. in ordinary pail, 4265. 



Time before milk in steamed pail soured, 28-g- hours. 



Time before milk in ordinary pail soured, 23 hours. 



If an imperfectly cleaned pail had been used for this 

 purpose, the difference in souring would have undoubt- 

 edly been more apparent. 



To illustrate the varying germ content of cans cleaned 

 in different ways, Harrison 1 rinsed out cans with 100 cc. 

 of sterile water, and then determined the germ content of 

 the same. The following data represents the number of 

 bacteria per cc. in the rinsing water from cans improperly 

 cleaned (series A), from cans washed in tepid water and 

 then scalded the usual factory method ( series B ) and 

 from cans washed in tepid water and steamed for five 

 minutes (series C.). 



Effect of steaming on germ content of cans. 



Series A (Dirty cans) .. 238,525, 342,875, 215,400, 618,200, 806,320, 



510,270, 230,100, 610,510, 418,810, 317,250. 

 Series B (Ordinary 



cleaning method)... 89,320, 84,750, 26,800, 24,000, 38,400, 



76,800, 15,200, 13,080, 44,160, 93,400. 

 Series C (Approved 



method) 1,170, 1,792, 890, 355. 416. 



36. Cleaning 1 dairy utensils. Milk vessels should 

 never be allowed to become dry when dirty, for dried 

 particles of milk residue are extremely difficult to remove. 



1 Harrison, 22nd Kept. Ont. Agr'l. Coll., p. 113. 1896. 



