Heating or Cooking. 185 



of curd readily unite, and in breaking them apart 

 again more fat is lost. Hence as soon as the curd 

 is cut, gentle agitation of the whole mass should 

 begin. This agitation should be sufficient to cause 

 the particles to move upon one another, but not 

 violent enough to break them up. The curd rapidly 

 shrinks and hardens ; more rapidly upon the outside 

 than the inside. This soon results in the formation 

 of a so-called "membrane," which not only tends 

 to prevent the particles from sticking together, but 

 affords some resistance to further breaking up. This 

 "membrane" is pervious to water, but retains the 

 globules of fat ; so as soon as the contraction has 

 reached this point, or when the curd is well "healed 

 over," the further expulsion of the water should be 

 aided by heat, and this point begins the third step. 

 Period III., heating or cooking. — The term "cook- 

 ing," as applied to the manufacture of cheese, is a 

 misnomer so far as it relates to any change in the 

 composition or condition of the material through 

 the effect of heat. By cooking any ordinary sub- 

 stance is meant the application of a degree of heat 

 sufficient to cause a coagulation of albuminous sub- 

 stances or a breaking down of starchy ones. The 

 degree of heat used in cheese making during this 

 stage never reaches anywhere near this point, and 

 never, except in rare instances, is a temperature of 

 blood heat exceeded. The change to be brought about 

 in this process is wholly the contraction of the curd 

 and the consequent expulsion of water from within 

 the particles. To this end the heat serves a two- 



