Pasteurization of Milk 



15 



ience of plant operation, these tanks 

 do cool down they must be heated up 

 to the pasteurizing temperature before 

 the milk is allowed to flow in. 



Chemicals that can be employed as 

 a germicide in milk should not be 

 used as a part of the cleaning of 

 pasteurizing apparatus. The pasteur- 

 izing treatment of milk is a physical 

 treatment of the application of heat to 

 che milk, and in this, chemicals play 

 no part. Chemicals used as a part of 

 this cleaning can be removed only by 

 thorough draining and rinsing, and a 

 careless and inefficient rinsing would 

 leave a residue of chemical in the ap- 

 paratus that may of itself or its cor- 

 rosive action on the metals of the appa- 

 ratus, cause a condition in the milk 

 flowing into it that might have a seri- 

 ous effect on the milk consumer. The 

 use of such chemicals in cleaning pas- 

 teurization apparatus should be pro- 

 hibited. 



(4) Some Dangerous Defects in 

 Pasteurization Apparatus. Pasteuri- 

 zation apparatus is inherently danger- 

 ous that shows the following defects : 



(a) That has a milk pipe leading 

 from the bottom of the heating or 

 holding tank or tanks to the cooler, 

 either direct or through a pump that 

 depends on a milk cock in this pipe as 

 a stoppage or safeguard, to prevent the 

 raw milk or the partially heated milk, 

 or heated but not held milk, from flow- 

 ing to the cooler, mixing with and in- 

 fecting the finished product. No milk 

 cock is secure against leaks since a 

 milk cock may be tight for months 

 and may leak through at any time. A 

 bristle of a brush, a thread, a bruise in 

 cleaning, or uneven contraction after 

 expansion, may cause a seepage leak 

 that utterly destroys the efficiency of 

 pasteurization which the apparatus is 

 supposed to effect, and this may hap- 

 pen without the knowledge of the most 

 careful operator. 



(b) That utilizes a rotating valve 



having connections from the heater 

 to the holding tanks and to the cooler. 

 With such a valve, abrasion or cutting 

 may occur at any time without the op- 

 erator's knowledge, which will form a 

 channel between the connections lead- 

 ing to the various tanks that may 

 shorten the holding time. Should a 

 channel in the valve be cut from the 

 holding tank connections to the cooler 

 connection, the heated, but not held 

 milk, will pass directly to the cooler 

 and mix with the finished product. 

 Efficient pasteurizing apparatus can be 

 constructed without using valves or 

 mechanisms with which the milk comes 

 in contact and that require lubrication 

 with vaseline or other kinds of grease. 



(c) That has a series of tanks for 

 holding the milk through which the 

 milk flows continually, that does not 

 consist of enough tanks to prevent a 

 current from forming and flowing 

 through the whole system, and that 

 does not have in each tank a device to 

 diffuse the inflowing milk and a device 

 to collect the outgoing milk that pre- 

 vents the formation of currents in the 

 milk. All holding systems of this type 

 should have at least three tanks and 

 their net efficiency should be proven by 

 color tests. 



(d) That has a by-pass pipe from 

 the raw milk tank to the cooler, cut- 

 ting out the heater and the holder, or 

 from the heater to the cooler, cutting 

 out the holder; such a pipe is not nec- 

 essary and might be used as a time 

 saver and is an invitation towards il- 

 legal and dangerous methods. 



(e) That is connected up to use the 

 same pump to empty the holding de- 

 vice at the end of the run that is used 

 to pump the raw milk. An apparatus 

 that requires a pump to force the raw 

 milk through the heater, holder and 

 cooler, when set on an approximate 

 level, will leave the holder full of milk 

 at the end of the run. This milk 

 should be pumped through the cooler 



