CHAPTER VII 



ECONOMIC BACTERIA IN MILK AND MILK PRODUCTS 



Cream Ripening. Bacteria in Butter-making. Control of the Ripening 

 Process. Bacteria in Cheese-making. Number of Bacteria in Cheese. 

 Kinds of Bacteria present in Cheese. The Use of Artificial Cultures in 

 Cheese-making. Abnormal Cheese Ripening and Poisonous Cheese. 



In the elementary and provisional classification of bacteria found 

 in milk, one group is set apart to include the organisms which are 

 neither pathogenic or to be classified wholly under the organisms of 

 fermentation. It is true many of them fulfil their life function by 

 setting up fermentation. But this is so to speak only a means to 

 an end. The end and result of their activity is beneficial in the 

 economy of nature and in the applications of nature to manufacture. 

 They bring about the ripening of cream and they flavour butter 

 and cheese. It is not unlikely that as our knowledge increases this 

 group of "economic" bacteria in nature generally, and in milk in 

 particular, will become larger and attract more and more interest. 

 In them man possesses powerful allies. Therefore, we have deemed 

 it desirable to insert in the present volume a short chapter deal- 

 ing provisionally with what is at present known respecting these 

 organisms and their function in milk, cream, butter, and cheese. 



Cream Ripening 



The number of organisms found in cream is enormous. Pro- 

 bably no other natural medium contains more. We have frequently 

 examined fresh cream in the country and found it to contain more 

 than ioo,0(X),ooo bacteria per c.c. It is not only a favourable medium. 

 It is the filter, so to speak, of milk. For as the cream rises the milk 

 parts with more than 90 per cent, of its contained bacteria. Conn 

 and Esten^ found 1 10,000,000 of bacteria per c.c. in unripened cream 

 (average of four examinations) and 284,000,000 in the same cream 

 ripened (average of four examinations). Cream obtained from 

 a creamery gave an average on eight examinations of 56,000,000 



1 Thirteenth Annual Report of the Starrs Agricultural Expt. Sta., Con- 

 necticut, 1900, pp. 13-33. 



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