EVAPORATED MILK MOJONNIER CONTROLLER 153 



milk may be expected to withstand the sterilizing heat without 

 danger of curdling in a manner that would render the product 

 unmarketable. 



The purpose of the viscosity test, of sample cans having 

 passed through the pilot sterlizer or controller is, to 'determine 

 whether the evaporated milk of the entire batch, without treat- 

 ment will safely pass through the adopted, standard sterilizing 

 process, or to what extent this process must be modified, or to 

 what extent the product, before sterilization must be treated 

 with bicarbonate of soda to secure a good body, and at the same 

 time insure freedom from the formation of a permanent curd 

 when applying the standard sterilizing process. 



A certain degree of viscosity in evaporated milk is desirable 

 and necessary in order to give the product a .good body and to 

 prevent the separation of the butter fat. . 



But. as the viscosity increases a point is reached beyond 

 which it is not safe to go, because of the danger of the formation- 

 of a permanent curd that renders the product unmarketable. 



The increasing viscosity is due to a change in the physical 

 properties of the protein constituents of evaporated milk result- 

 ing from the action of heat. The earlier stages of these changes 

 are desirable, because they result in a product of good body and 

 of increased stability of emulsion. An excessive continuation 

 of these changes precipitates the proteins in the form of visible 

 particles of curd which, if permanent, spoil the product for the 

 market. 



Factors which Influence the Viscosity and their Correlation 

 to the Sterilizing Process. The extent to which heat increases 

 the viscosity of evaporated milk is dependent on many and vary- 

 ing conditions, such as acid of milk, natural stability of proteins 

 in milk as related to their behavior toward heat, degree of con- 

 centration of evaporated milk, degree of heat applied in fore- 

 warmer, amount of extraneous water in evaporated milk, degree 

 of heat in the sterilizer, duration of exposure to sterilizing heat. 

 The resistance of the proteins to heat, as affected by these sev- 

 eral conditions and factors, can be modified and largely con- 

 trolled if necessary, by the treatment of milk that has an ab- 

 normally low resistance to heat, with definite, small quantities 

 of bicarbonate of soda. 



