Part II.] PASTEURIZATION OF MARKET MILK. 105 



of the United States Dairy Division has done some very ex- 

 tensive work along this line covering a period of seven years, 

 and has found that, while this objection may have been true 

 in the earlier days of pasteurization, when very high tem- 

 peratures were used, milk pasteurized at lower temperatures, 

 such as 145° F. with the holding process, as now is almost 

 universally practiced in market milk plants, sours normally and 

 in a similar manner as raw milk. This shows that enough of 

 the lactic acid bacteria survive to remove this objection. My 

 own experiments on pasteurization of cream, conducted during 

 the last five years at Purdue University, further show that the 

 putrefactive germs are killed at the same ratio as the lactic 

 acid bacteria, and that properly pasteurized cream is, there- 

 fore, much freer from these undesirable germs. 



It has been further argued that pasteurization does not de- 

 stroy poisonous products already present in the milk before 

 pasteurization. While this is perfectly true, it is equally true 

 that pasteurized milk is no worse than raw milk in this respect 

 inasmuch as these products are obviously also present in the 

 raw milk. 



Another very widely argued claim has been that pasteurized 

 milk is less digestible than raw milk; that the soluble albumen 

 becomes insoluble; that part of the ash, and especially the 

 valuable lime salts, are precipitated; that the casein is altered 

 in its physical make-up; and that the enzymes which aid in 

 digestion are rendered inactive. These changes do occur, to a 

 limited extent at least, in milk heated to temperatures near 

 the boiling point (212° F.). But the fact that they do take 

 place does by no means prove that they render milk less di- 

 gestible. Comparative experiments, conducted by nutrition ex- 

 perts in this country and abroad with babies in hospitals and 

 also with calves, dogs, cats, rabbits, rats and other animals, 

 do not uphold these assumptions. In fact, the bulk of the 

 now available evidence on this subject is favorable to the 

 digestibility of pasteurized milk. Even the precipitation of 

 the lime salts by heat does not render the mineral matter of the 

 milk less digestible, the lime in the heated milk being utilized, 

 digested and assimilated quite as well as the lime of normal 

 raw milk. The important protein compounds of milk, such as 



