136 Repoet of the Bacterioloqist of the 



different temperatures. So far as data were at hand this had 

 been done but twice in America. Both of these tests had been 

 carried out at about 70° C. (158° F.) and the trials were too few 

 in number and the results too contradictory to form a safe basis 

 for generalization. 



At the Wisconsin Station^ it was found that, while there was 

 considerable variation in the effect of a heating of G7.3°-T4° C. 

 (15')°-! 05° F. ), in some cases as many as 10 per ct. of the 

 bacteria survived and in the tests published this number remain- 

 ing amounted to over 2,000,000 germs per cubic centimeter. 



A different kind of continuous machine was used at the Penn- 

 sylvania Station^ and no numerical residts were given, but it was 

 stated that "Heating to this temperature 67.3°-70° C. (155°- 

 158° F.), for this length of time, as was found by culture plates, 

 destroyed few, if any, of the bacteria present in the milk." 



Since 70° C. (158° F.) is the lowest temperature which is gen- 

 erally recommended for continuous pasteurizing this was taken 

 as a starting ]ioint in our work and when the effect of this tem- 

 perature had been observed higher degrees were used. 



MACHINE USED. 



We are indebted to D. 11. Burrell & Co., Little Falls, X. Y., 

 for the loan of a continuous pasteurizer made by Konstantin 

 Hansen & Schroder, Kolding, Denmark. This has a rated capac- 

 ity of 2,500 pounds of milk per hour heated to 70° C. (158° F.) 



The accompanying drawing of a cross section (Plate II) ex- 

 plains the essential parts of the machine. The milk enters at the 

 bottom into a central milk chamber. Here it is set in motion by 

 the stirrer revolving 300 times per minute, which spreads the 

 milk out in a thin layer against the wall and finally expels it at 

 the tangential milk outlet above. This outlet has a lateral opcn- 



4 Pastourization as Applied to Butter Making, Wis. Agr. Exp. Sta. Bui. 09. 



5 Heated Milk for Butter Making, Penn. Agr. Exp. Sta. Bui. 45. 



