THE RELATION OF MICROORGANISMS TO MILK 



453 



EFFECT OF INITIAL CONTAMINATION ON DEVELOPMENT OF BACTERIA AND KEEPING 



QUALITY OF MILK 



Milk Having Moderately High Initial Contamination 

 Bacteria per c.c. in fresh Bacteria I2 hours Bacteria 36 hours Hours to curdling 



187,000 



432,000 



45 



Milk Having Moderate Initial Contamination 



Milk Having Small Initial Contamination 



milk starting out with different numbers of organisms was kept under 

 similar conditions until coagulation. Plate cultures made from these 

 three samples show the relative development of the number of 

 organisms. 



These samples were all kept at a constant temperature of 21 and 

 the difference in the numbers of bacteria and the curdling time can 

 therefore be fairly attributed to the difference in the initial contamina- 

 tion of the three samples. All three of the samples showed a normal 

 development of the lactic organisms, which constituted over 99 per 

 cent of the total organisms present at the time of curdling. While 

 this may be considered as showing the normal effect of the original 

 contamination upon the milk, it is well to bear in mind the fact that 

 there are many apparent exceptions due to some particular type of 

 organism predominating and interfering with the normal development 

 of the lactic types. 



STRAINING. The straining of milk is one of the most common 

 operations in connection with its handling and is considered by most 

 dairymen as one of the most essential from the standpoint of the qual- 



