No. 6. DEPARTMENT OF AGRICULTURE. 613 



equal, and this will have to be determined by the cheese-maker with 

 each new lot of extracl, enii>loying the i-egular rennet test. The 

 guide to kee}> in mind iu determining- how much rennet to use is 

 this: Use enough renuet to curdle the milk in fifteen to twenty 

 miuutes for a quick-curing cheese, and, in ^:hirty to forty minutes, 

 for a slow-curing cheese. The rennet extracts in common use are 

 added at he rate of two and one-half to live ounces for 1,000 pounds ot 

 milk, but generally at the rate of from three to four ounces. 



(3.) Method of Adding Rennet Extract. — The rennet extract must 

 be diluted with twenty to forty times its own volume of water, which 

 may be cold or at a temperature of 85 degrees F. to 90 degrees F. 

 The object of dilution is to prevent uneven action of rennet on the 

 milk. If undiluted rennet extract is added to a vat of warm milk, 

 the portions of the milk first coming in contact with the renuet 

 coagulates at once before the rennet has a chance to reach the whole 

 body of milk. The diluted extract acts much less quickly and gives 

 one time to mix it uniformly and thoroughly, through the whole mass 

 of milk. Some makers prefer to dilute the rennet with cold water 

 instead of warm, on the ground that the cold vrater keeps the rennet 

 inactive longer and thus gives a longer time in which to mix the 

 rennet completely through the mass of milk. 



Just i)revious to adding the rennet extract, the milk should be 

 thorougiily stirred, and then the diluted rennet should be poured 

 into the milk eve«ly from one end of the vat to the other. The milk 

 is at once gently but thoroughly stirred again so as to mix the rennet 

 completely and uniformly with it, and the gentle stirring is con- 

 tinued for several minutes. Then the surface of the milk is stirred 

 quietly with the bottom of a dipper to keep the fat from separating, 

 this movement being kept up for about half the time required to co- 

 agulate the milk but stopping before there is any appearance of 

 coagulatiom. A cloth is then placed over the top of the vat, if neces- 

 sary, to keep the surface of the milk from cooling, and the milk 

 is kept undisturbed while the coagulation takes place. The rennet 

 does not act instantaneously so as to- show any visible signs, the 

 first indication of acting being a slight thickening of the milk, shown 

 by the slowness of drops of milk to fall from a thermometer or 

 other object dipped in the milk and held up so as to allow the milk 

 to drip from it. The coagulation goes on gradually until the whole 

 mass of milk is one solid, continuous chunk of coagulum or curd, 

 the result of changing milk casein into paracasein. In this process, 

 the fat-golbules and also the other milk constituents are imprisoned 

 in the paracasein. 



53. Cutting the Curd. 

 The object of cutting the curd is to permit the whey to go out of 

 the paracasein. This takes place much more rapidly and completely, 



