526 



MILK 



COMPARISON OF BACTERIAL REDUCTION OF PASTEURIZATION IN BOTTLES AND EOT- 

 TLING HOT PASTEURIZED MILK 



The authors claim for the process of bottling hot, pasteurized 

 milk that the cream line is not affected to a greater extent than by 

 ordinary methods of pasteurization. 



The apparatus for the process designed by Ayers and Johnson 

 is shown in Fig. 215. 



The same authors state that it is a mistake to judge bacterial 

 efficiency of pasteurization by percentages. A standard should 

 be adopted as has been done in judging the efficiency of water 

 purification plants. Pasteurization of milk with low bacterial 

 content will naturally show a smaller percentage of efficiency than 

 pasteurization of milk with large numbers of bacteria. The pas- 

 teurized product of the former will still contain fewer bacteria 

 than the product of the latter. Therefore it is difficult to estab- 

 lish fair standards at present. The commission on standards of 

 the New York Milk Committee has considered 50,000 bacteria 

 for milk and 100,000 for cream a fair standard. In a measure 

 such standards involve the same difficulty as do standards for 

 raw milk, since they do not show whether the pasteurizer or sub- 

 sequent handling are at fault. 3 



Hammer and Hauser made a series of experiments with pas- 

 teurization in the final package by immersing the filled bottles 

 in water of a temperature ranging from 140 to 170 F. The 

 best results were obtained by immersion at 145 F. for fifty min- 

 utes. Milk pasteurized by this method soured much as does raw 

 milk of good quality. The cream line suffered slightly, in some 

 instances more than in others, but on the average not sufficiently 

 to be objectionable. A heated flavor developed, but this also 

 was so slight as to pass unnoticed by the majority of consumers. 



1 Bottles were washed clean in hot water before they were filled with 

 raw milk. 



2 Bottles were steamed two minutes and cooled before they were filled 

 with raw milk. 



3 The principal kinds of pasteurization apparatus, cooling devices, and 

 bottling machines are described by Ayers in Circular 184, United States 

 Dept. of Agri., B. A. I., 1912. 



