Pasteurization of Milk 



11 



the sterilization of such a cooler is to 

 flow boiling water down over it; even 

 the expansion caused by this heat may 

 buckle the surface and prevent proper 

 sterilization. The sterility of a cooler 

 can be determined by flowing sterile 

 water over it after the cooler has been 

 allowed to cool. 



All open surface coolers should have 

 removable metal covers to protect the 

 milk, or should be installed in a prop- 

 erly constructed room that is not used 

 tor any other purpose. Milk should 

 be fed to open surface coolers through 

 a perforated pipe that does not permit 

 foam to gather, as the collection of 

 foam is often favorable to large bac- 

 teria growths. 



From the cooler the milk flows to a 

 cold milk tank of relative small dimen- 

 sions that has an agitator to keep the 

 cream from raising. It is not necessary 

 to insulate this tank under usual con- 

 ditions. From this tank the milk flows 

 to the can filler and the cans, and to 

 the bottle filler and the bottles. 



(e) Pumps. Milk pumps should be 

 eliminated from milk plants wherever 

 possible ; where their use is necessary it 

 is preferable to use a pump large 

 enough to handle the milk at a moder- 

 ate speed. As the pump must come 

 apart every day for cleaning, pumps 

 with few parts that are accessible for 

 cleaning and are put together with 

 strong bolts, are the best type. The 

 stuffing boxes on either the piston or 



, rotary type pump must be opened up, 

 cleaned and packed with clean packing 

 every day. Off flavors in the milk are 

 sometimes caused by the putrid milk 

 that accumulates in the stuffing box, 

 corrodes the metal and seeps into the 

 milk. 



Milk pumps should not be installed 

 to pump milk after it has been heated 

 if this can possibly be avoided, since 

 this practice increases the liability of 

 contamination. 



(f) Stuffing Boxes. Stuffing boxes 



in vats, tanks or other apparatus are 

 to be avoided wherever possible, and 

 if used, must be cleaned and packed 

 clean every day. If not kept in first 

 class order, they are likely to cause 

 corrosion and off flavors in the milk. 



(g) Fittings and Valves. All ma- 

 chinery, apparatus, pipes and pipe fit- 

 tings, and valves used for pasteurizing 

 milk, must be so constructed as to 

 permit every part with which the milk 

 comes in contact of being opened up 

 and scrubbed with a brush. There 

 must be no cracks, crevices or inac- 

 cessible corners, nor must there be any 

 absorbent or spongy material used in 

 construction. Gaskfets should be elim- 

 inated, but if they are necessary in 

 some types of apparatus, heavy paper 

 gaskets should be used and renewed 

 daily. 



(h) Metals Used in Construction 

 of Apparatus. Apparatus constructed 

 of copper, tinned and with tinned 

 bronze castings, has given satisfaction 

 in many plants, both before and after 

 the tin has worn off. Tinned copper 

 pipe, and red brass fittings for milk 

 cocks, have given satisfactory service. 

 Any metals, alloys or combination of 

 metals that produce electric action 

 when subjected to the condition of a 

 milk plant should be avoided, as the 

 decomposed metal may cause off fla- 

 vors in the milk. 



(i) Temperature Control Appar- 

 atus. Temperature control of heating 

 the milk for pasteurization may be ob- 

 tained by using the well known and 

 practical temperature controllers on 

 the market; the sensitive part of the 

 instrument is preferable placed in the 

 water circulation to the milk heater, 

 when a suitable type of heater is used, 

 or it may be placed in the hot milk dis- 

 charged from the heater. In all cases 

 small valves in the steam line should 

 be used, as their opening and closing 

 does not cause such fluctuation in tem- 

 perature. In almost all cases steam 



