Heating or Cooking 255 
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 cyrd 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- 
