CARE OF MILK AND CREAM 41 



results obtained from a sample of milk which was thor- 

 oughly mixed and then divided into six equal parts. 

 The six bottles were then placed in water at different 

 temperatures for twelve hours, at which time the germ- 

 content of each lot was determined. The six bottles 

 were then all placed together in a temperature of seventy 

 degrees and allowed to remain until they curdled. As 

 each sample curdled, the time was recorded. The 

 difference in the germ-content and the keeping time is the 

 result of the difference in temperature for a period of 

 twelve hours only, and shows what may easily happen in 

 milk which is allowed to stand over night without thor- 

 ough cooling. 



"EFFECT OF DIFFERENT TEMPERATURES FOR TWELVE HOURS 

 ON THE GROWTH OF BACTERIA AND ON THE KEEPING 

 QUALITY OF MILK 



I II 



Kept at 45 degrees Kept at 50 degrees 



Number of bacteria, 9,300. Number of bacteria, 18,000 



Curdled in 75 hours Curdled in 72 hours 



III IV 



Kept at 55 degrees Kept at 60 degrees 



Number of bacteria, 38,000 Number of bacteria, 453,000 



Curdled in 49 hours Curdled in 43 hours 



V VI 



Kept at 70 degrees Kept at 80 degrees 



Number of bacteria, 8,800,000 Number of bacteria, 55,300,000 



Curdled in 32 hours Curdled in 28 hours " 



According to Ross and Mclnerney, 1 " Most germs 

 thrive best at a temperature of about 98 F., or 36.6 C., 



1 Ross, H. E., and Mclnerney, T. J., Cooling Milk, Cornell 

 Reading Course Lesson, No. 102, 1915. 



