OHAPTEE XX 



ARTIFICIAL METHODS FOE THE PEESERVATION OF MILK 



It is a matter of common knowledge that milk will not keep 

 fresh for any length of time. Scientifically this has been 

 shown to be due to the fact that milk (as has been abundantly 

 demonstrated in earlier chapters), as produced at the present 

 day, is heavily contaminated with bacteria, and that such 

 bacteria multiply rapidly in milk. The products of the 

 bacteria spoil the milk. Added to this we have the fact that 

 under modern conditions some delay is inevitable between 

 the collection of the milk and its consumption, and in 

 the case of large cities this interval may have to be many 

 hours. 



The utility if not the necessity of using some artificial 

 method for the preservation of milk is therefore widely 

 recognised. All such methods may be included in the 

 following groups : 



I. Eefrigeration. 

 II. Sterilisation. 



III. Pasteurisation. 



IV. Addition of chemical preservatives. 

 V. Condensatioa and drying. 



Each procedure requires to be considered from the following 

 points of view : 



(a) Its efficiency to attain the object aimed at. 



(&) Any prejudicial effect upon the milk as an article of 



human food, 

 (c) Its influence upon the price at which the milk can 



be supplied. 



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