SWEETENED CONDENSED MILK COOLING 109 



The pressure required to pump the sweetened condensed 

 milk through the cooling coil and up into the holding tanks 

 varies from about 800 to 1200 pounds, and the pump used for 

 this purpose must be strong enough to develop a pressure of 

 at least 2,000 pounds, which may be required to start the flow 

 through the coil after the milk has stood idle for some time and 

 has become chilled. 



This method, in addition to its labors-saving feature, and 

 to its efficiency in avoiding sandy and settled condensed milk, 

 has the further important advantage, that the product is pro- 

 tected against contamination with bacteria, mold, and other im- 

 purities from the air, etc., the product being under seal until 

 it reaches the filling machine, or until it is packed into barrels 

 in the case, of bulk goods. This method, therefore, should be 

 particularly adapted for efforts to produce an article that does 

 not develop "buttons" with age. See also Chapter on "Defects 

 of Sweetened Condensed Milk." 



The chief criticism that may be raised against this method 

 lies in the question of cleaning the cooling coil. From the 

 standpoint of bacterial contamination it may safely be said, 

 however, that the danger of such contamination is remote. After 

 the product of one day's make has passed through the coil, the 

 coil is sealed by valves and there is no reason to doubt that 

 the condensed milk remaining in the coil till next day's opera- 

 tion, is not just as well protected against all contaminating 

 influences, as if it were sealed in tin cans. It is advisable, how- 

 ever, to completely empty and rinse and steam the submerged 

 coil at regular intervals of say once per week. This is especially 

 desirable in the case of a copper coil, in order to guard against 

 an excessive accumulation of copper salts which would tend 

 to lend the product a metallic flavor and to jeopardize its whole- 

 someness. In the case of a black iron coil, sand-blasted on inside, 

 the effect of the action of the acid and sugar of the milk is 

 negligible. However, when not filled with condensed milk the 

 iron coil should be kept filled with clean water to prevent exces- 

 sive rusting. 



