1 66 PRACTICAL DAIRY BACTERIOLOGY 



500,000 bacteria per c.c. After some days the bacteria will begin 

 to develop and eventually become abundant, but during the first 

 few days after its preparation it is possible to transport such 

 material for long distances, and yet place it on sale in a city 

 in a better condition, at least so far as bacteria are concerned, 

 than most of the milk which now reaches the larger markets. 

 4. The expense of the transportation of such milk is very much 

 reduced because of the decrease in bulk. 5. The concentrated 

 milk is itself pasteurized, and because of its method of prepara- 

 tion is thoroughly pasteurized. The condensation of the milk 

 is not possible by this method except by long-continued heating 

 at, at least, a temperature of 140, and this is sure to complete 

 the pasteurization. This low temperature is not sufficient to 

 give any cooked taste or apparently to produce any chemical 

 changes except the evaporation of the water, in this respect 

 being much better than pasteurization at a higher temperature ; 

 but it is sufficient, as shown by careful tests, to destroy the 

 pathogenic bacteria of milk. For these reasons concentrated 

 milk promises great aid in solving the milk problem of cities, 

 since it offers at a low price milk that cannot be distinguished 

 from ordinary milk, and yet can be guaranteed as free from 

 pathogenic bacteria; and it will keep well. Attempts are being 

 made at present to put this product upon the market in this 

 country. 



Milk Powder. Many attempts to reduce milk to a powder 

 have been made with more or less success. 1 The devices for 

 this are several and need not concern us. In all cases where 

 milk is reduced to a powder it is capable of being kept for a 

 long time. Where the milk contains the cream, however, the 

 reduction to the dry powder does not prevent its eventually be- 

 coming rancid, and powdered whole milk will not keep indef- 

 initely. Powdered skim milk will keep without much trouble. 



1 Jensen. Rev. Gen. d'Lait, IV., 1905. 

 Huyge. Rev. Gen. d'Lait, III., p. 320, 1904. 



