CHAPTER III 

 CONTAMINATION OF MILK 



Milk, meats, eggs, fruits, etc., are classed as perishable food 

 products, for unless extraordinary means are taken to preserve 

 them, the period during which they can be used as food is 

 limited. Of these milk is the most perishable. The period 

 during which it can be kept is measured by hours rather 

 than by days. The spoiling of these products is due to the 

 growth of bacteria and other organisms in and on the surface. 

 The more perfectly the product is adapted as food for organ- 

 isms, and the greater the number which gain entrance to it, 

 the shorter will be its period of usefulness. No other food 

 product is to be compared with milk as a culture medium 

 for bacteria, and, curiously enough, no other food product is so 

 exposed to contamination during the process of preparation. 



No 'subject in dairy bacteriology is more fundamentally 

 important than that relating to milk contamination, both in 

 the factory and on the farm, and most of the problems relating 

 to the proper handling of milk come back to this question. 



The contamination of milk may be considered from three 

 standpoints, hygienic, economic, and what may be called the 

 standpoint of general cleanliness. From the hygienic stand- 

 point are to be considered the contamination with pathogenic 

 bacteria and the production of poisonous and injurious sub- 

 stances in the milk by the growth of saprophytic bacteria. 

 The economic side of the question has to do with the dimin- 

 ished keeping quality of milk and of other dairy products, 



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