and loss of butter-fat in the whey. Most cheesemakers therefore prefer rennet when they can get it.
The rennet having been added, the milk is left undisturbed until a firm curd has been formed. When the curd breaks or splits sharply before the finger pushed slowly through it, it is ready to be "cut."
Cutting.—Two sets of curd knives are used, each
consisting of a metal frame in which tinned steel blades
are hung, in one vertically
and in the other horizontally.
The vertical knife is first carried
slowly through the curd
lengthwise and crosswise; the
horizontal set of blades is
then moved carefully through
the length of the vat. When
the cutting is over, the entire
mass should be in cubes about
half an inch square.
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Curd knives
The whey that begins to separate out should be clear and yellow. Milky whey is a sign that the butter-fat is escaping in it; the curd has been broken up too violently. In curdling, the casein encases the butter-fat and the object of the breaking up of the curd in the vat is to expel the whey but retain the fat in the cheese.
"Cooking" the Curd.—Gentle heat is now applied to
raise the temperature gradually to 98° or 100° in the
course of about 30 minutes. Meanwhile the small
pieces of curd are kept floating in the whey by gentle
