PASTEURIZATION 211 



ture of 70 C. (158 F.) for their destruction, and some 

 will even survive boiling. Therefore, there is no cer- 

 tainty that all toxins which may be present in milk will 

 be destroyed even if the milk is boiled. While there 

 is no direct proof that milk containing toxins is injurious 

 to health, at the same time we are also without positive 

 knowledge that such milk is harmless ( see page 45 ) . 



Although there is no definite information regarding 

 the effect of heat upon the cleavage products resulting 

 from the breaking up of the milk constituents by bac- 

 teria, we have reason to believe that they are not all 

 destroyed by heat. This is an important point because 

 some of these substances are of a harmful character. 



In the light of our present knowledge regarding the 

 effects of pasteurization upon toxins and cleavage prod- 

 ucts, it would seem advisable to limit the production of 

 these substances as much as possible by protecting the 

 milk from bacterial contamination and by promptly 

 cooling it and keeping it cool until it is pasteurized. There 

 should be a limit to the number of bacteria which may 

 be present in milk which is to be pasteurized, and this 

 limit should be as low as circumstances will permit. 



4. Nutritive Properties. The statement is fre- 

 quently made that milk may be heated at 145 F. (62.8 

 C.) for thirty minutes without affecting its nutritive 

 properties, but this is not confirmed by the experience 

 of Hess, who saw scurvy develop in from two to three 

 months in nearly every one of a group of infants who 

 were being fed on milk pasteurized in that manner ; when 

 orange juice or potato water was added to the milk the 

 disease was cured. The observations of Plantenga indi- 

 cate that this diseased condition is not due entirely to 

 the effect of heat on the milk. He reports that while 



