TRANSPORTATION PROBLEMS 189 
“flash” pasteurization. Generally speaking, this type is apt to 
be less efficient than the discontinuous pasteurizers, and are more 
subject to irregularity. Either type is efficient if properly man- 
aged, but carelessness and haste on the part of the employees may 
render either kind unreliable and inefficient. 
In the last few years the plan of pasteurizing the milk on a large 
scale has come to be frequently adopted. It is done in creameries 
in connection with butter-making, and in many of our large cities 
and in some of our states it is required for the treatment of the general 
milk-supply. Pasteurization serves another purpose that appeals 
to the milk-dealer. Milk distributers have found it difficult to 
furnish milk that will keep without preservatives, but have learned 
that the application of heat enables them todoso. For this reason 
pasteurization has become adopted by almost all large milk 
companies. 
One of the latest developments in regard to pasteurization 1s 
the use of apparatus to heat the milk after it is already bottled. 
The advantage of pasteurization in the bottle has long been 
realized. No other method of pasteurization entirely excludes 
the danger of contamination during bottling. Mechanical difh- 
culties, however, have prevented the development of such a 
process until recently, because the expansion of the milk during 
heating makes the ordinary method of sealing the bottles im- 
possible. Recently these mechanical difficulties have been over- 
come, and pasteurization in the bottle promises to become an 
important process in the future. 
Preparations of Milk.—The microdrganisms that spoil milk 
will not grow in it if the water is removed, and several methods 
have been devised for producing a form of milk that will keep, all 
of which are based upon the removal of the water. Condensed 
milk is the oldest and has a wide use. It consists of ordinary milk 
evaporated to about one-third of its original bulk, to which is 
commonly added a large amount of sugar. The sugar prevents 
the growth of bacteria, and this condensed milk, put up in cans, 
