TYPES OF MICROORGANISMS IN CHEESE 287 



000; 1:1,000,000 and 1:10,000,000. Lower dilutions 

 may be necessary if the cheese has been stored for some 

 time. 



8. Incubate the plates at 25 C. for three to five days. 



9. Count and estimate the number of microorganisms 

 per gram of cheese. What types predominate? Why? 



10. Transfer the different types to litmus milk and note 

 the action after several days. Which of these types, as 

 determined from the action on litmus milk, may have a 

 prominent part to play in the ripening of the cheese? Why? 



12. Do microorganisms play any part in the formation 

 of the flavor of cheddar cheese? Other cheeses? 



How does the cheese analyzed compare with the butter 

 analyzed as to numbers and types of microorganisms? 



What qualitative tests are made for milk used for cheese 

 making? What is the principle and application of these 

 tests? 



What cheese " abnormalities " may be caused by 

 microorganisms? During what stages' in the process of 

 making cheese may these occur? 



What pathogenic organisms have been found in cheese? 

 What is known of their longevity in this medium? 



13. State your results and conclusions in full and point 

 out any practical applications. 



REFERENCES 



LOHNIS: Laboratory Methods in Agricultural Bacteriology, pp. 83-88. 

 RUSSELL and HASTINGS: Experimental Dairy Bacteriology, pp. 



103-109. 



MARSHALL: Microbiology, pp. 346-357. 

 CONN: Practical Dairy Bacteriology (1907), pp. 223-259. 

 SAVAGE: The Bacteriological Examination of Food and Water (1914), 



pp. 118-119. 

 DECKER: Cheese Making (1905), pp. 48-51, 63, 66, 69, 75, 88, 108- 



110. 

 VANSLYKE and PUBLOW: The Science and Practice of Cheese-making 



(1912), pp, 115-135, 285-312, 371-378, 



