13 



is no chance of the system coming into practical use, as the 

 difficulties are too great when the system has to be applied 

 on a commercial basis. 



PRESERVING BY ELECTRICITY. 



This, like butter and cheesemaldng by electricity, has been 

 talked about, but while experiments seem to have proved that 

 electricity may, to a certain extent, paralyze microbes, nothing 

 practical has been evolved as yet, as far as I know. 



PRESERVING BY HEAT. 



It has been shown how the bacteria germs develop best 

 at about blood heat and how their development is reduced 

 all the more, the colder they are kept, but excessive heat has 

 a. better effect it kills them. This has been known for ages 

 and the preservation of milk and cream by boiling is a com- 

 mon precaution among housekeepers. 



Yet, unless the milk is cooled down and kept cool, the 

 effect is only to keep it sweet for 12 to 24 hours longer and 

 the boiled taste, to which so many people object, prevents its 

 general use. This taste is much more pronounced in milk 

 heated in open vessels than in milk sterilized under steam 

 pressure in the modern apparatus, and yet there is the same 

 objection of its being made less digestible by the coagulation 

 of the albumen. Compare the digestibility of a soft boiled 

 and a hard boiled egg or that of a raw and boiled oyster. 



In creameries the heating of the skim milk to nearly boil- 

 ing point (195) without cooling, is often miscalled pasteuriza- 

 tion, but it has been proved by actual experiments in Den- 

 mark that though pasteurization may be better if the milk is 

 cooled properly and the patrons' cans are cleaned before fill- 

 ing, the expense of cooling is too great, and hence, it is far 

 better simply to heat the milk to such a degree that it will kill 

 the bacteria in the little milk left in the unwashed cans. Here 

 also have the creamery men been satisfied with heating, though 

 I fear that in too many cases, the temperature is too low to 

 do effective work. 



PRESERVATION OF MILK BY CONDENSING. 



Although the idea was first suggested in the beginning 

 of the 19th century by the Frenchman Appert, it was not until 



