202 PASTEURIZATION 



used, the ice box in the rear of the vat, or the separate tank of 

 the positive system, serves to dissolve the ice and the ice water 

 is circulated in a similar manner as the hot water. Water and 

 brine usually enter the coil under pressure, in which case they 

 circulate on the principle of the positive circulating system. The 

 water exhausts into the sewer and the brine is pumped back into 

 brine tank above or returns to the brine tank by gravity if the 

 latter is located in the basement. In order to avoid excessive 

 weakening of the brine by the water remaining in the coil, it is 

 advisable to not only give the coil as many turns as there are 

 rungs in the spiral after the water is shut off, and before the 

 brine is turned on, but to allow the exhaust of the coil to run 

 off, after the brine has been turned on until the exhaust begins 

 to taste briny. 



Steam, water und brine connections should be at least of 

 equal size as the inlet to the vat. If they have to be brought 

 from a considerable distance it is recommended that they be 

 at least one pipe-size larger than the vat inlet. The pressure 

 on the disc machines should not exceed 5 to 10 Ibs. and that 

 on the coil machines about 35 pounds per square inch. 



Operation of Vat Pasteurizer. The use of a forewarmer be- 

 fore the cream reaches the vat pasteurizer is not so essential in 

 the holding process of pasteurization as in the flash process. 

 The standardization of cream for acid and for fat may be. and is 

 often done in the pasteurizing vat. However, the forewarmer 

 is a convenient dumping vat and is used in most. creameries in 

 connection with either vat or flash pasteurization. 



If the cream is sour, or part sweet and part sour, it is 

 advisable to raise the temperature in the vat pasteurizer slowly 

 to about 115 degrees F. and then rapidly to 145 degrees F. in 

 order to avoid abnormal curdling. In extreme cases of curdling 

 difficulties it may even be necessary to hold the cream at about 

 115 degrees F. for a while. This slow heating below 125 de- 

 grees F. gives the curd an opportunity to contract and harden 

 in the usual way, so that when the higher temperature is reached, 

 the formation of a rubbery and sticky curd and loss of fat as the 

 result of intense action of heat and acid on the soft casein, is 



