PASTEURIZATION OF MILK OK CREAM 283 



as to the relative number of each kind, to the fermentation 

 of milk or cream, to spore formation, and to resistance. 

 Which microorganisms have succumbed to pasteurization 

 at different temperatures and which were able to withstand 

 it? 



14. Record the results obtained from the study of plates 

 and cultures made from colonies. 



15. Record your observations from day to day of macro- 

 scopical changes in the pasteurized and unpasteurized con- 

 trol tubes. Does pasteurization destroy organisms that 

 are favorable, or detrimental to the milk? What influence 

 does pasteurization have upon the keeping quality of 

 milk? . 



16. What influence do the following factors have upon 

 the efficiency of pasteurization: the age of milk? acidity? 

 degree of temperature to which milk is subjected? dura- 

 tion of pasteurization temperatures? presence or absence 

 of air? pressure, whether atmospheric or greater? viscos- 

 ity or other changes in milk or cream? 



What changes are accomplished by pasteurization? 

 Why is milk pasteurized? Is this end always accomplished 

 in commercial plants? 



What different methods are used commercially for the 

 pasteurization of milk? What are the advantages and 

 disadvantages of each method? Why? 



At what stage in the process of production should 

 milk be pasteurized to accomplish the desired results? 

 Must the after-treatment of pasteurized milk be any differ- 

 ent from that of unpasteurized milk? 



Do you think that milk should be pasteurized before 

 it reaches the consumer? 



Does pasteurization affect the digestibility of milk? 

 What are the limitations of pasteurization as applied to 

 milk? 



17. Give your results in full and any conclusions that 

 may be drawn. 



