260 MILK 



"roughly, 60 per cent, of the organisms will be found in the bowl 

 sediment (separator slime); 25 per cent, in the separated milk, 

 and 15 per cent, in the separated cream," 



The writer, together with Luckhardt and Hicks, working with 

 40 per cent, cream, found that the skimmed milk running from the 

 separator contained an average of 2130 bacteria per cubic centi- 

 meter, while the cream contained 132 bacteria per cubic centi- 

 meter and the original milk 738. The cream contained 17 per 

 cent, of the germ content of the milk, not taking into account the 

 number thrown into the separator slime. The total germ con- 

 tent per cubic centimeter of the final product after the milk and 

 cream were reunited was, therefore, considerably greater than 

 that of the original milk. This result is in agreement with the 

 work of Severin, who explains the phenomenon on the ground 

 that clumps of bacteria are broken up by the centrifugal force, 

 and that then the colony count increases, although the actual 

 number of cells is diminished by the loss in the bowl sedi- 

 ment. 



The writer and Class attempted later to harmonize the con- 

 tradictory results reported by various authorities. The work was 

 carried out by regulating a hand separator in such a manner as 

 to obtain cream of varying richness. The 99 tests made covered 

 cream of different fat content from 16 to above 55 per cent. 

 The experiments demonstrated that 1, cream fresh from the 

 separator, as a rule, contains less bacteria than the original milk; 

 2, the number of bacteria in separator cream decreases propor- 

 tionately as the fat content increases; 3, the number of bacteria 

 in separator milk is larger than the number in the milk from 

 which it was obtained if the cream contains up to about 35 per 

 cent, of fat. Above this percentage the number is smaller; 4, 

 the number of bacteria in separator milk decreases proportionately 

 with the increase of fat in the separator cream. The results are 

 graphically illustrated in Fig. 84. 



Similar results were obtained by Lamson, who states that 

 "there is a slight indication that an increase in butter-fat results 

 in a decrease in percentage count of bacteria." 



The decrease of bacteria coincident with the increase of fat 

 in centrifugal cream is readily explained by the following reason- 

 ing : Bacteria cling to the fat globules and move toward the center 

 of the separator, but during this time the centrifugal force gradu- 

 ally releases them from the fat and they are thrown into the 

 skimmed milk and to some extent into the slime. The longer the 

 centrifugal force exerts this influence, the larger is the number 

 of bacteria that are released from the fat. The richness of the 

 cream in the separator used for these experiments is regulated by 



