MILK-PLAiSTT OPERATTON", 5 



In order to pasteurize milk properly, two things are necessary: 



1. The milk must be heated to 145° F. and hold for 30 minutes 

 with an accurate control of the temperature and time. After heating 

 and holding, the milk must be immediately cooled to 50° F. or below. 



2. All apparatus which comes in contact with the milk must 'be 

 cleaned thoroughly and sterilized after each using. 



Unless there is an automatic temperature control the steam and 

 water valves must be carefully watched in order to maintain the proper 

 temperature. If the milk is not heated to the proper temperature 

 and held at that temperature, good results can not be expected. 

 All pipes or ''pockets" in which milk is held during the pasteurizing 

 or holding process should be insulated, as otherwise the holding tem- 

 perature can not be maintained. Great care must be used also that 

 none of the valves leading from the heater or holder leak. Milk 

 coming from the pasteurizer should never pass through any apparatus 

 which has contained raw milk. 



The cleansing and sterihzing of the apparatus is absolutely essen- 

 tial for good results. All milk pipes, pumps, and filler valves, as 

 well as the pasteurizer, should be taken apart after each run, thor- 

 oughly cleaned and rinsed, and then sterilized by steam. An abun- 

 dance of steam should be used. Unless all bottles and cans are 

 thoi'oughly cleansed and sterilized the value of the pasteurization 

 will be greatly reduced. 



The proper pasteurization of milk is a simple operation and there 

 is little excuse for the poor results that are obtained at some plants. 

 Poor results are usually not the fault of the type of pasteurizer 

 used, but of the way in which it is operated. 



Following are some of the causes of poor pasteurizing results at 

 milk plants : 



Pipes and pumps not cleaned and sterilized. 



Filler and valves not cleaned and sterilized. 



Milk rushed tlirougli the apparatus too fast. 



Milk not heated hi^h enough nor held long enough. 



Temj^erature recorder not accurate. 



Bulb thermometer not accurate. 



Raw milk added to pasteurized milk in vat before the pasteurized lot is all drawn 

 out. 



Pumps and piping not of sanitary construction. 



Leak,v or inaccurate valves, whicli allow some of the milk to get through the appa- 

 ratus without being held the proper length of time. 



Formation of foam in the holder. 



Great care should be taken that valves in the pipe line do not 

 leak. Leaky valves are a very common occurrence in many milk 

 plants, and besides the very insanitary character of such a con- 

 dition much loss of milk results from it. The prevention of milk 

 loss is an important part of the manager's duties, and no pains 

 should be spared to keep all valves and connections in the milk 

 lines tight. 



CONTROL OF PASTEURIZING TEMPERATURE. 



One of the most important considerations in the proper pasteuriza- 

 tion of milk is control of the temperature. In order to do this 

 properly an automatic device is necessary. It is diflicult and often 

 impossible to control the temperature by means of hand valves, 

 but there are on the market automatic devices which will control 

 the temperature very accurately. 



