NUMBER AND TYPES OF BACTERIA IN BUTTER 285 



9. What is the melting-point of butter? Are bacteria 

 ordinarily killed at this temperature? 



What kinds of microorganisms are found in fresh butter 

 from ripened cream? In old butter? In fresh oleomar- 

 garine? In renovated butter? In canned butter? 



Do bacteria increase or decrease in butter kept in stor- 

 age? What other methods of making a bacteriological 

 examination of butter may be employed? 



Are microorganisms in any way responsible for the 

 flavors of butter? Explain. 



What pathogenic organisms may gain entrance to 

 butter? 



What is the avenue of entrance? How long can bacteria 

 exist in butter? How do bacterial numbers and types 

 compare with those of fresh milk? of ripened cream? 



10. Give your data and conclusions in full and point out 

 any practical applications, 



REFERENCES 



RUSSELL and HASTINGS: Practical Dairy Bacteriology, pp. 95, 97. 



LOHNIS: Laboratory Methods in Agricultural Bacteriology, pp. 

 81-82. 



MARSHALL: Microbiology, pp. 335-345. 



SAYER, RAHN and FARRAND: Keeping Qualities of Butter, I. Gen- 

 eral Studies, Tech. Bui. I (1908), Mich. Agrl. Expt. Sta. 



RAHN, BROWN and SMITH: Keeping Qualities of Butter, II and III. 

 Tech. Bui. 2 (1909), Mich. Expt. Sta. 



WELLS, LEVI: Renovated Butter: Its Origin and History. Year- 

 book of Dept. of Agr. for 1905, pp. 393-398. 



ROGERS, L. A.: Studies Upon the Keeping Quality of Butter, I. 

 Canned Butter. Bui. 57, B. A. I., U. S. Dept. of Agr. (1904), 

 pp. 6-8, 22-23. 



