8 BULLETIN 240, U. S. DEPARTMENT OF AGRICULTURE. 



machines is shown in figure 3. The machine consists of a large tank 

 divided into two compartments and two smaller tanks. These con- 

 tain water at different temperatures. Bottle-holding frames are car- 

 ried through these compartments on an endless chain in the manner- 

 shown in the drawing. The raw milk is bottled and capped with 

 water-tight caps, then placed on the bottle-holding frames of the 

 machine on the loading end. The bottles of milk are then carried 

 through the preheating compartment into the pasteurizing compart- 

 ment where they remain for about 30 minutes. From the pasteuriz- 

 ing tank the bottles are carried to the cooling tank, then to the 

 refrigerating tank, after which they are removed from the machine. 

 The process is continuous, the bottles of milk being loaded at one 



f H. P. MOTOR 



Fig. 3. — Machine for continuous pasteurization of milk in bottles. The bottles have 

 water-tight caps and are conveyed on an endless chain .through water compartments 

 of various temperatures. 



end, heated, held, and cooled, then unloaded at the other end of the 

 machine. The temperature of the water in this machine is auto- 

 matically controlled. 



There are other machines on the market which differ in the man- 

 ner in which the bottles are carried through the tanks of water, but 

 the principle is about the same. 



In other types of pasteurizers the bottles are not submerged in 

 water and consequently water-tight caps are not necessary. The 

 bottles of milk arc heated and cooled by sprays of water and ordinary 

 caps are used and protected from water by a metal covering. One 

 of this type of in-the-bottle pasteurizers is shown in figure 4. The 



