14 



The American Public Health Association 



Apparatus may be so constructed 

 that it will do efficient pasteurization 

 and the milk develop a satisfactory 

 cream line when the quantity of milk 

 handled does not require the raising 

 of the temperature of the heating 

 medium to more than a few degrees 

 above the temperature to which the 

 milk is to be heated. When more 

 milk than can be properly handled is 

 forced through such an apparatus, the 

 heating medium must be raised in tem- 

 perature to maintain the temperature 

 of the milk, with the result of impair- 

 ing, if not eliminating, the cream line. 



(k) Cleaning and Sterilizing Appa- 

 ratus. The whole pasteurizing appa- 

 ratus must be thoroughly cleaned 

 every day; nothing but thorough 

 cleaning should be tolerated regard- 

 less of any reasons for careless clean- 

 ing that may be offered. Every par- 

 ticle of grease film must be removed 

 from the apparatus as grease film is 

 very favorable to bacteria growth^. 



Immediately after the finish of the 

 run,' the milk should be rinsed of? with 

 cold water and every part of the ap- 

 paratus opened up and scrubbed with 

 brushes and cleaning powder. Where, 

 owing to the heat, a deposit from the 

 milk has formed, this deposit must be 

 cleaned off by using an abrasive clean- 

 ing powder, if necessary, and all thor- 

 oughly rinsed, first with cold water 

 then with hot water. 



Wash sinks preferably of metal, long 

 .enough to take the milk pipe and hav- 

 ing drainage racks for rinsing, should 

 be placed conveniently so that all milk 

 pipe, milk fittings, cocks, etc., which 

 must be taken apart at every point 

 every day, can be placed in these sinks 

 and soaked for an hour or so before 

 scrubbing. After each and every part 

 has been scrubbed clean and bright, 

 it must be rinsed with clean cold and 

 then hot water, and the apparatus as- 

 sembled. 



After the apparatus has been put 



together and is ready for operation, it 

 must be sterilized. To sterilize, con- 

 nect the steam supply at 10 pounds 

 pressure to the various parts of the 

 apparatus so that the steam will reach 

 every part, using great care to drip 

 off all water of condensation which 

 would accumulate in any part and pre- 

 vent the steam from heating it up, and 

 also cause uneven expansion produc- 

 ing great strains in the apparatus. If 

 high pressure steam is used for steril- 

 izing, its greater velocity and higher 

 temperature causes much more rapid 

 heating of that part of the apparatus 

 with which it comes in direct contact, 

 and consequently, greater expansion of 

 the metal at that point, setting up 

 physical strain that will reduce the 

 durability of the apparatus. In any 

 part of the apparatus that will not 

 stand pressure, lids should be closed 

 down as tightly as safety permits, so 

 that the steam may be confined as 

 much as possible. Metal pipe or metal 

 hose should be used for sterilizing 

 steam connections to any part of the 

 apparatus with which the milk comes 

 in contact as rubber hose disintegrates 

 and deposits black specks which will 

 appear in the milk. 



It usually takes from two to three 

 hours to sterilize completely an ap- 

 paratus with 10 pounds of steam. To 

 determine whether sterilization has 

 been effected, collect samples of the 

 condensation water from the various 

 parts of the apparatus and if bacterio- 

 logical examination shows these to be 

 sterile, the apparatus is in good order. 



The heater and ' cooler should be 

 sterilized after the washing is finished, 

 or long enough before the milk is run 

 to become cool before any cold water 

 is turned into them. The holding 

 tank may be sterilized at the same time 

 as the heater and cooler, but must not 

 be permitted to cool down below the 

 pasteurizing temperature when the 

 milk is run. If, owing to the conven- 



