522 



MILK 



this means the milk cannot leave the machine without having 

 passed through the entire system (Fig. 210). 



Several tank types of holding machinery are manufactured. 

 The tank may be divided into a series of compartments (Fig. 211) 

 in order that the milk may flow freely from one compartment to 

 the next. 



As has been stated earlier, experience has taught that the 

 more frequently milk is handled, the greater is the probabiUty 

 of bacterial contamination. This applies to milk after pasteiuiza- 

 tion quite as well as to the production of raw milk. After milk 

 has been pasteurized by either process it is collected in a large 

 tank and then piped to a bottling machine. This exposes it to 



Fig. 211. — Tank retarder with compartments. (S. H. Ayers in Circular 184, 

 Bureau of Animal Industry, U. S. Dept. of Agriculture.) 



contamination in the pipes, the bottling machine, and the bottles. 

 In well-managed plants the chances of reinfection are greatly 

 reduced by the use of suitable machinery and efficient super- 

 vision of the same. To avoid this menace of reinfection an- 

 other process has been proposed and is carried out in some 

 dairies in this country. This process is pasteurization in the final 

 package. 



3. Pasteurization in the final package means that the milk is 

 bottled and then pasteurized. The bottles are immersed in water 

 which is gradually warmed to the desired temperature. After 

 the milk has reached the proper temperature it is held for thirty 

 minutes and then cooled. The cooling may be effected by chill- 

 ing the surrounding water, or the bottles may be sprayed first 



