PASTEURIZATION OF MILK AND OTHER METHODS 

 OF REDUCING THE GERM CONTENT 



The problem of conserving perishable foods has engaged the 

 attention of man from the remotest period of his existence to the 

 present day. The real cause of food decomposition or food 

 "spoiling" was not understood before the era of bacteriology, the 

 science which taught that minute organisms were nearly omni- 

 present, and that through their activity food was rendered value- 

 less for man. However, several efficient methods of food conser- 

 vation were evolved even among savage tribes. The production 

 of butter, cheese, and fermented milks was the natural conse- 

 quence of such attempts. Conservation has also been effected 

 by the application of heat and cold; by desiccation; by the use of 

 harmless preservatives, such as sugar and acid, and by the use 

 of chemical preservatives. Heat, with its destructive, and cold, 

 with its restraining, effect upon micro-organisms are probably 

 the most successful and most commonly apphed assets of food 

 conservation. Both are extensively apphed to the preservation 

 of milk. 



When it was discovered that micro-organisms caused milk 

 "spoiHng," it seemed feasable to apply heat to prolong the period 

 during which milk could be kept sweet. Soxhlet in 1866 had 

 special bottles made which were filled with milk, then closed 

 tightly, and immersed in boihng water. The milk was exposed 

 for a short time to a temperatm"e near the boihng-point of water. 

 Soxhlet erroneously thought that milk treated in this manner was 

 sterilized. However, good results were obtained by feeding this 

 milk to babies, and in 1889 Jacobi first recommended the Soxhlet 

 method for the preparation of milk in this country. 



Milk heated to the temperature of boihng water undergoes 

 profound physical and chemical changes. Taste and appearance 

 are altered, and in a measure the nutritive value is affected. These 

 alterations have been dealt with previously (see page 131). In 

 order to avoid these changes a method similar to the one first used 

 by Pasteur for the preservation of beer and wine has been devised 

 for milk and has found considerable favor. "Pasteurization" was 

 originally designed for preservation of milk, but the term has been 

 used rather loosely. At the present time the advantage of pre- 

 serving milk has been more or less lost sight of in view of the 

 success attained by efficient pasteurization in destroying disease 



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