146 MILK HYGIENE 



ture of the milk can be raised above the boiling point, 

 and through these the milk is forced by means of a small 

 pump. There is a large number of such machines. In 

 Germany they are commonly used for simple pasteuriza- 

 tion. Of the machines most used in recent years, the 

 so-called "regenerative heater" is to be commended be- 

 cause it saves much steam. It is built according to the 

 principle that the hot milk flows past the entering cold 

 milk (only a thin metal plate separating them) so that 

 both streams of milk have opposite directions; by this 

 means, there is the advantage that the hot milk, even 

 before it leaves the sterilizer, is somewhat cooled with- 

 out expense, while the cold milk gains quite a little heat 

 before it is heated by the action of the steam. In this 

 way steam, as well as ice, is saved. Machines built in 

 accordance with this principle differ much in appear- 

 ance. Some, for example the apparatus shown in Fig. 

 10, which is one of the newest, consists really of two 

 parts, the sterilizer proper (the "high pressure pasteur- 

 izer") and an apparatus quite similar ("the regenera- 

 tive heater") in which the stream of warm milk works 

 upon the incoming cold milk. Both parts have the same 

 construction, which is easily seen from Figs. 10 and 11. 

 Other machines of this kind (for example, Mor's re- 

 generative milk heater, Fig. 12), are simpler in that 

 both processes take place in the same machine. For 

 sterilizing milk measured into bottles, machines which 

 are described and figured on pages 136 and 137 (Fig. 9) 

 are used. 



