62 SWEETENED CONDENSED MH,K HEATING 



best, much of the steam used condenses in the milk, increasing 

 the* amount of water that has to be evaporated. It, therefore, 

 prolongs the process of condensing and increases the cost of 

 manufacture. This is especially true where the boilers are 

 located at some distance from the hot wells and the steam pipes 

 are not well insulated, causing the steam to be "wet," and when 

 the milk to be heated is cold. It is estimated that the amount 

 of extraneous water thus added to the milk increases the bulk 

 .of the milk by about one-sixth of its original volume. The steam 

 is often associated with impurities, such as cylinder oil from 

 the engine, boiler compounds used in the boilers, scales from the 

 inside of the pipes, etc. These various impurities cannot possbily 

 improve, but may seriously injure the quality of the milk. It is 

 generally conceded by those who have given this matter, careful 



Fig-. 14. Steam rosette for heating- milk 

 Courtesy of Arthur Harris & Co. 



thought, that the turning of steam direct into the milk shortens 

 the life of the product and causes it to develop a stale flavor, 

 which may degenerate into an oily flavor. The same defect is 

 noted also when cream is heated by turning steam into it. The 

 prolonged exposure of the milk to the condensing process, as the 

 result of the addition to the milk of considerable quantities of 

 condensed steam, is an additional objection. 



From the above discussion it is obvious that the heating of 

 the milk by bringing it in direct contact with free steam has 

 some objections. Just to what extent this practice jeopardizes 

 the quality has not been very conclusively demonstrated. But 

 it is recommended that the heating with direct steam, if it must 

 be practised, be confined to the last stages of the heating process, 



