CHAPTER IV.* 



RELATION OF MICROORGANISMS TO SOME SPECIAL 



DAIRY PRODUCTS. 



GENERAL. 



There are a number of special dairy products which do not normally 

 come into a discussion of market milk, butter or cheese, but which are of 

 considerable importance. A book of this sort would not be complete 

 without a discussion of some of these products from the bacteriological 

 point of view. Most of these special products have been developed as 

 commercial enterprises and the processes of manufacture have been 

 zealously guarded as trade secrets. The result is that there is very little 

 available data on the manufacture of these products and very little 

 authoritative knowledge about their bacteriological condition. It is, 

 therefore, difficult to give a full discussion of the microbiology of these 

 products. A few of the more important ones will be discussed, however. 



CONDENSED MILK. 



There are at least three quite distinct kinds of condensed milk made 

 under conditions which result in an entirely different bacteriological 

 condition in the finished product. These different products must, there- 

 fore, be considered separately. Condensed milk means simply milk 

 from which a large part of the water has been removed, thus decreasing 

 its bulk, the purpose being to lessen the cost of transportation and to 

 increase the keeping quality of the product. Water is removed from 

 milk by some process of heating, either with or without vacuum, the 

 heating process being more or less equivalent to pasteurization. 



SWEETENED CONDENSED MILK. This product is made by removing 

 a large part of the original water by means of heat and the addition 

 of cane sugar. It is then put up in sealed cans. It is not intended to be 

 sterile. The degree of heat to which it is subjected is not sufficient to 



* Prepared by W. A. Stocking. 



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