66 HOUSEHOLD BACTERIOLOGY 



resisting microbe destroyed, a third steaming is given. 

 This is called intermittent sterilization. No. 5 should 

 keep indefinitely. It will, of course, dry away slowly 

 through evaporation. 



No. 6 is like No. 5, only closed from the air which 

 passes through the cotton wool, and if the cork was 

 sterilized it is impervious to dust. Some corks are not 

 solid enough to keep the bacteria from growing 

 through the cavities. Such corks need to be dipped 

 in melted paraffin. They are then as tight as a glass 

 stopper. No. 6 should keep, as well as No. 5. 



The woman who put up her grape juice in corked 

 bottles, to find some years after that she had grape 

 wine, either did not thoroughly sterilize the juice, the 

 bottles and the corks, or the latter allowed dust to pass 

 or mold to grow through. She should have covered 

 the corks with melted paraffin to prevent such a pos- 

 sibility. 



No. 7 varies from No. 5 only in the time and the 

 degree of heat to which it was subjected. In the case 

 of milk where the process is most commonly used 

 this is called Pasteurization. It is sufficient to kill 

 most if not all the souring bacteria and all the disease- 

 producing or pathogenic germs. It does not affect as 

 unfavorably the digestibility of the milk as steriliza- 

 tion, 212 F, or higher is found to do. 



Pasteurized milk will spoil eventually because not 

 all the germs are killed. Pasteurization is valuable for 

 protection from disease germs and to improve the keep- 



