are added at the rate of from one-half to five ounces for 1000 pounds of milk. Before adding, the extract should be diluted with from 20 to 40 times its volume of water at a temperature of from 85 to 90 degrees. The rennet thus diluted acts with uniformity on the milk, preventing the production of curd of a lumpy character. Previous to adding the rennet extract the mass of milk is thoroughly stirred in order to mix the fat therewith and the dilute rennet added evenly and slowly with constant stirring which is continued for several minutes. A gentle stirring of the surface of the milk should be continued until the curd is at least half formed, in order that the fat may not separate. After the stirring is finished, a cloth is placed over the top of the vat to keep the surface of the milk from cooling, and the milk is then left undisturbed until the coagulation is complete. The coagulation goes on gradually until the whole mass of milk is one solid coagulum produced by the changing of casein into paracasein.
Cutting the Curd.—In order that the whey may be separated it is necessary that the curd be cut into pieces. The smaller the pieces of curd, the more rapidly will the whey escape. As soon as the curd is formed it shows a tendency to contract and this tends to force out the whey. By cutting the extent of the surface from which the whey can exude is amplified and the rapidity of the process is enormously increased. The time at which the curd is to be cut is one of great importance and is determined by the skill and experience of the cheese maker. If the curd is cut when it is too soft there may be large loss of fat and a decreased yield of cheese. If the curd is too hard the whey is more difficultly removed and the quality of the cheeses is not so fine. The following test is used to determine when the curd is in the right condition to cut. The end of the index finger is inserted obliquely into the curd half an inch or more and then slowly raised toward the surface. If the curd breaks apart with a clean fracture without leaving any particles on the finger and the whey which exudes from the broken surface is clear and not milky it shows the proper time has come for cutting. Specially devised knives are used for cutting the curd, which leave it in small cubes of about one-half inch surface. Skill in the use of the cutting knife is important and can only be acquired by proper experience.
Heating the Curd.—As soon as the curd is cut the whey begins to go out of it and the curd settles to the bottom of the vat, the whey being of a higher specific gravity than the curd. After the pieces of curd sink to the bottom the surface easily reunites and, when broken apart, additional fat is lost. As soon, therefore, as the curd is cut the whole mass is kept in gentle motion by hand stirring or with a wire basket designed for the purpose, care being taken to avoid breaking or comminuting the cubes. When properly stirred the whey appears clear and is free of small particles of curd.
The curd contracts and hardens during this process, and soon reaches a
