MILK SURVEY OF THE CITY OF ROCHESTER 187 



This is further indicated by the samples taken from the mixing tanks 

 of the pasteurizing plants. Thirty-four of these were taken and 31 con- 

 tained bacteria in excess of two hundred thousand, while 17 contained 

 bacteria from one to five million indicating very unsanitary milk. The 

 samples taken from the heaters of the pasteurizers were 14 in number. 

 Two of these contained bacteria of between two and five hundred thou- 

 sand, and four bacteria from fifty to one hundred thousand. These six 

 samples indicated plainly that the processes of heating were ineffective. 

 The failure to destroy bacteria in the milk must be reported as due not 

 so much to lack of proper temperature on the part of the heating appar- 

 atus, for as the temperature seemed to be sufficient, the only remaining 

 reason for these large number of bacteria after heating must be imper- 

 fect cleansing and sterilization of the apparatus. 



Eighteen samples were taken from the holding tanks. Four of these 

 contained bacteria between fifty and two hundred thousand, while eight 

 contained bacteria between twenty-five and fifty thousand. These 12 

 samples all show plainly that the process of pasteurization was ineffective, 

 since a first-class heating and holding process should result in milk which 

 contains not more than ten thousand bacteria. Since the temperatures on 

 most of these machines seemed to be sufficiently high, the chief reason 

 for the large number of bacteria must be due to imperfect processes of 

 washing and sterilization of the pasteurizing apparatus. 



The 22 samples taken from the cooling apparatus in the pasteurizing 

 plants show the same indications of imperfections in the pasteurizing 

 processes. 



Passage of the milk from the cooler does not indicate any marked 

 increase in the numbers of bacteria, there being 10 samples containing 

 bacteria ranging from twenty-five to two hundred thousand, which corre- 

 sponds rather closely with the bacteria in the samples for the holding 

 process. 



Samples of milk taken from bottle filling apparatus were 12 in all. 

 Two of these contained bacteria between one hundred and two hundred 

 thousand, one between two and five hundred thousand, and one between 

 one and five million. 



There were 46 samples taken from filled bottles after all processes 

 were complete. Six of these contained from one to two hundred thou- 

 sand bacteria; three from two hundred to five hundred thousand, and 

 four from five hundred thousand to a million, and two from one million 

 to five million, making in all 15 samples out of forty-six, or 30% of the 

 bottled milk samples in excess of one hundred thousand bacteria. All 

 of these were bottles of pasteurized milk and the large numbers of 

 bacteria in them plainly indicate unsanitary conditions in the washing 



