EVAPORATED MILK-^ SHAKING 159 



be cooled to a low temperature. All abuses of milk along these 

 and similar lines are bound to cause trouble in the sterilizer, 

 which is avoidable and unnecessary. 



Finally there are factors which are not under control but 

 which' also exert a very marked influence on the behavior of 

 the product toward sterilizing heat at times. These are invari- 

 ably associated with changes in the period of lactation, changes 

 in feed and climatic conditions and their effect on the amount and 

 proportion of the protein .and ash constituents of milk, as ex- 

 plained in Chapter XXIII, "Defective Evaporated Milk, Lumps 

 of Curd." These conditions are not only not controllable, but 

 their effect on the milk is not determinable by any now known 

 practical method of analyses. 



Proper attention to the controllable conditions will go far 

 in making unnecessary the use of bicarbonate in evaporated 

 milk and will at least confine its use, when necessary, to very 

 small amounts. When these conditions have been conscientiously 

 taken care of and, in spite of these precautions, certain batches of 

 milk, because of the above named effect of uncontrollable fac- 

 tors, require the use of bicarbonate in order to insure safe ster- 

 ilization and to avoid loss, then the emergency justifies and 

 sound judgment and business efficiency demand recourse to 

 methods that the helping hand of science has made available, 

 so long as these methods do not impair the wholesomeness and 

 food value of the product, although their ethics, in principle at 

 least, cannot be approved for general practice. See also /'Effect 

 of Relation of Mineral Constituents of Milk," Chapter XXIII, 

 "Defective Evaporated Milk." 



SHAKING. 



Purpose. The purpose of shaking the evaporated milk is 

 to mechanically break down the curd that may have been formed 

 in the process of sterilization and to give the contents of the cans 

 a smooth and homogeneous body. 



The high temperatures to which the evaporated milk is sub- 

 jected in the sterilizer have. a tendency to coagulate the casein. 

 In the case of normal, fresh milk the casein coagulates at a tem- 

 perature of 269 degrees F. In the evaporated milk, made from 

 perfectly normal and sweet, fresh milk, the casein curdles at 

 much lower temperatures, and the higher the ratio of concentra- 



