QUESTIONS 345 



perature for at least four hours iu order that the butter fat may 

 have time to solidify, or temper. 



When once thoroughly soured and cooled, cream may be held 

 for a day or two if necessary without great injury. The pres- 

 ence of the lactic acid prevents most other forms of bacteria from 

 growing, whereas if it were endeavored to keep the cream sweet 

 by low temperature for four or five days it is probable that a 

 bitter, unpleasant-flavored bacterial growth would have occurred. 



Fig. 115. —Showing the effect of temperature on rate of growth of bacteria. 

 a at 50° F., b at 70° F. 



. 2. The creamery system consists first in pasteurizing the 

 cream for the purpose of destroying all, or as many as possible, 

 of the bacteria that were brought in by the patrons and then 

 souring or ripening it by means of a starter prepared from a 

 pure culture grown for the purpose. A starter is essentially 

 only a quantity of clean-flavored sour milk used to hasten and 

 to control the growth of bacteria in the cream. This process is 

 too long and complicated for farm dairy use. 



QUESTIONS 



1. What relation is there between care of cream on the farm and price 



received for the finished butter? Explain. 



2. How does cold temperature of cream preserve its quality? 



3. How long after separating is it safe to try to keep cream before it is 



made into butter? 



4. What difference in price is it fair to make between sweet, clean cream and 



that which is sour and off flavor? 



5. What is meant by cream ripening? 



6. Why is cream ripened? 



7. How is cream ripened? 



8. May cream be ripened too much? 



9. What is meant by tempering cream ? 



10. Briefly, what is the creamery system of cream ripening? 



