PASTEURIZED MILK 69 



and keeping qualities than that from unsanitary milk. 

 Milk of doubtful sanitary quahties is an existing evil, and 

 pasteurization is a present and efficient remedy. 



2. Produces Chemical Changes in Milk. — The chemical 

 changes wrought in milk by the heating process are said 

 to render milk less digestible and to cause rickets and scurvy 

 in children. 



The pasteurization of milk for adults, however, can be 

 no more objectionable than the cooking of meat. It is 

 sterilization and high temperature pasteurization which 

 cause changes in milk, while on the other hand, a tempera- 

 ture of 145° F. for twenty minutes (as is commonly used 

 in commercial pasteurization) does not appreciably affect 

 its physical and chemical properties. 



Nature did not intend that milk should be cooked, neither 

 did nature intend that milk should be exposed to bacterial 

 contamination and unfavorable surroundings, and be al- 

 lowed to undergo fermentative changes for a day or two 

 before being consumed. 



An excessively high temperature, especially if prolonged, 

 will, it is true, decompose some of the proteins, diminish 

 the organic phosphorous, increase the inorganic phos- 

 phorous, precipitate the calcium and magnesium salts and 

 phosphates, expel most of the carbon dioxide, partially 

 carameUze the lactose, cause a coalescence of some of the 

 fat globules, and coagulate some of the serum albumin. 

 Heat also destroys the enzymes which, according to some 

 authors, aid in digestion and metabolism. 



3. Desirable Lactic-acid Bacteria are Killed, while 

 Some Undesirable Types are not. — Since lactic-acid 

 organisms are not spore producers they have as low a 

 thermal death point as the pathogenic organisms, and are 

 killed by pasteurization. In raw milk the lactic-acid 



