PASTEURIZATION 205 



authors play a useful r61e in digestion and metabolism. We 

 have no direct knowledge of the utility of these ferments. 

 For the child to digest and assimilate cow's milk to advan- 

 tage the complex albuminous substances must first be 

 broken down by the processes of digestion into simpler 

 products and again synthetized. In other words cow pro- 

 teins must be converted into human proteins. In this pro- 

 cess enzymes play an essential r61e. We know that the 

 digestive tube contains ferments that dissolve and break 

 up the complex proteins into simpler substances, but con- 

 cerning the rearrangement of these simpler compounds into 

 forms best suited for assimilation we have little definite 

 knowledge. While ferments play an active part in both 

 the breaking-down and the building-up processes, it re- 

 mains for future investigation to determine what particular 

 ferments are helpful in the latter process. It has been 

 abundantly shown by laboratory work that the ferments 

 in milk, or most of them, at least, can withstand a temper- 

 ature ranging from 60° to 65° C. for some time without 

 material injury. Between 65° and 70° most of these are 

 weakened in their activity, and between 70° and 80° all of 

 them are destroyed even after relatively short exposure. 

 (Kastle.) 



Raw milk shows the peroxidase reaction, whereas milk 

 which has been heated for one hour at 70° C, or for shorter 

 intervals at higher temperatures, does not exhibit this 

 reaction. In this connection Kastle and Porch ^ have 

 observed that on heating milk to 60° C. for 20 min- 

 utes, the peroxidase reaction of many specimens of milk 

 is not only diminished but if anj^hing somewhat intensi- 

 fied. 



The following table (page 206) from Kastle and Roberts' 

 article on "Chemistry of Milk" in Hygienic Laboratory 

 Bulletin no. 41, p. 333, gives instructive data pertaining to 

 the destruction by heating of enzymes in general. 



1 Journal of Biological Chemistry, vol. iv, 1908, pp. 301-20. 



