PASTEURIZING MILK. 25 



Milk can be pasteurized by the ordinary holder system at 145° F. 

 for 30 minutes. It can then be bottled hot in special oversized milk 

 bottles of the ordinary type and capped with ordinary sterile caps. 

 Before being filled the bottles can be steamed for two minutes by 

 running the crates inverted on a conveyer over steam jets. The 

 bottles would then go through the bottling machine in a hot condi- 

 tion and would be practically sterile. The crates of hot bottled 

 pasteurized milk can then be cooled by stacking in a refrigerator 

 room and blowing cold air through the crates. In the cold season 

 outside air can be used for cooling, and in the warm season re- 

 frigerated air can be circulated through the crates. 



This process can be modified. The hot milk can be held in the 

 bottles at 145° F. instead of in a tank, and the crates of hot pasteur- 

 ized milk can be cooled by spraying with cold water instead of air. 



From the results of experiments with air cooling on a small prac- 

 tical scale started in 1913, it is believed to be entirely practical to- 

 cool hot bottled milk by means of forced-air draft. The results of 

 this work are being prepared for publication in the near future. 



Since the process of bottling hot pasteurized milk has not as yet 

 been worked out for practical use, it is impossible to state definitely 

 all its advantages and disadvantages. However, from laboratory 

 experiments alone certain advantages are plainly shown. From a 

 sanitary standpoint one great advantage of the process of bottling 

 hot pasteurized milk in hot bottles lies in the fact that bottle infec- 

 tion is eliminated. From a commercial standpoint there is also an 

 advantage, because of the reduction of milk losses on the cooler 

 caused by adherence of milk and by evaporation. Ordinary card- 

 board caps may be used in this system, since they do not have to be 

 water-tight, which is obviously a point of great advantage so far 

 as cost is concerned. 



At the present stage of this work it is impossible to state how the 

 cost of air cooling will compare with the ordinary methods in prac- 

 tice, but it is believed that there will be no more expense involved. 



The length of time required for cooling is perhaps the greatest 

 disadvantage of this process, and yet this would be of no consequence 

 except in plants where the milk is delivered immediately after 

 pasteurization. In the majority of milk plants the milk is pasteur- 

 ized in the morning or afternoon, placed in refrigerators, and deliv- 

 ered early the next morning. Consequently in most plants it would 

 make little difference whether the cooling process was performed 

 quickly or slowly. 



SUMMARY. 



1. The process of pasteurization in the bottle, using a temperature 

 of 145° F. for 30 minutes, causes satisfactory bacterial reductions. 



