STERILIZATION OF MILK. 153 



ties came in with this strong heating, however. The milk 

 assumed a brown color and acquired a burned or boiled 

 taste, whicl was generally objected to by consumers. 



Such milk cannot be used for baby-feeding. It is 

 furthermore very expensive, and difficult to arrange for 

 this heating on a large scale. It can only be done by 

 means of a so-called autoclave, or by the application of salt 

 solutions. It therefore proved impossible in many cases 

 to apply high temperatures for the sterilization of milk. 



Through Tyndall's and Gay-Lussac's investigations we 

 have learned, however, that sterility may also be obtained 

 in liquids by application of lower heating by the so-called 

 intermittent sterilization, which was already spoken of 

 in the Introduction (see p. 15). Hueppe seems to have 

 been the first one to apply this method for sterilization of 

 milk. He stated that it was only necessary to apply a 

 temperature of 167 F. (75 C.) for half an hour for 

 five consecutive days. It has been found, however, that 

 this method is not always reliable. Only where the re- 

 sults obtained can be controlled, as in laboratories by 

 testing in an incubator or similar apparatus, can they be 

 relied on. In my experiments, cultures of certain species 

 of potato bacilli in milk have stood such a treatment with- 

 out appreciably losing their vitality. We know bacteria 

 which develop well at about 158 F., a fact sufficient to 

 shake our faith in the reliability of a method of steriliza- 

 tion of the kind mentioned. This also shows the reason 

 why different scientists have come to such different re- 

 sults in their investigations of this subject. One states 

 that milk may be sterilized perfectly by repeated heating 

 to 167 F., and another that a considerably higher tem- 

 perature must be applied. The difference of results comes, 

 of course, from the fact that different bacteria were found 



