io CLEAN MILK 



heat from 163 F. to 167 F. The germ-destroying substance is 

 weakened by 149 F., acting for half an hour. 



Now, the important point lies in the fact that the disease germs 

 which occasionally are present in milk (germs of typhoid and scarlet 

 fever, diptheria, tuberculosis, cholera and streptococci and staphy- 

 lococci) may be killed by a comparatively low degree of heat (140 

 F.) without destruction of either the ferments or the germ destroy- 

 ing substance. 



Then there may be the poisons, spoken of above, to be con- 

 sidered. Those arising in milk from germ growth (toxines) we 

 have little knowledge of, but those we do know about (as the toxines. 

 of diphtheria and tetanus) are readily destroyed by a low degree of 

 heat (140 F. ) The poisons or ptomaines arising from the action 

 of spore-bearing germs in causing putrefaction of old milk are 

 found in pasteurized milk because heat does not kill these germs. 

 From what has been said it would seem that the temperature of 

 240 F. is most suitable for heating milk intended for infant food. 

 The time during which milk should be thus heated has been found 

 (Freeman) to be 30 minutes in order to effectively kill most germs. 



This, then, se'ems the best temperature and time for pasteuriz- 

 ing milk for infant food. Milk is more commonly pasteurized now 

 at higher temperatures. To be effective in killing germs pasteur- 

 ization should be done as follows: If milk is heated to 150 F., 

 it should be maintained at this point for 20 minutes; if to 160 F., 

 then it should be maintained for 15 minutes; if to 170 F., then it 

 should be maintained for 10 minutes. As a matter of fact, most 

 medical authorities have been in the habit of pasteurizing milk for 

 infants at 150 F. to 160 F. for 20 minutes. Authorities differ 

 somewhat as to the proper pasteurizing temperature. Pasteurizing 

 at a low temperature (140 F.) is chiefly important for infants — 

 not for adults. Park states that heating milk at the following points 

 will kill typhoid, tubercle and other non-spore bearing organisms : — 



For 10 minutes at 8o° C. (176 F.). 



