358 Milk and Its Products 



tub and the temperature maintained as nearly as possible at 98 F. for 

 six to twelve hours, when they may be examined. A solid, firm curd, 

 without disagreeable odor or flavor, shows that the milk is pure and 

 clean and has been properly handled. Impurities in the different sam- 

 ples are indicated by the presence of small round holes (gas cells) seen 

 in the curd when it is cut across with a knife, or by various disagree- 

 able odors that may be detected when the covers to the jars are removed. 

 The apparatus for this test in an improved form is now furnished by 

 most of the dairy supply houses. 



MONRAD RENNET TEST 



This test is figured and described on page 241. It is used as fol- 

 lows: To determine the ripeness of milk for cheese making, put 5 c. 

 c. commercial rennet in a 50 c. c. flask and fill with water to the mark. 

 Put 200 c. c. of milk at 86 F. in a suitable tin cup, and allow it to float 

 in the vat. Add 5 c. c. of the diluted rennet, and note carefully the time 

 required for the first appearance of coagulation. The time required 

 will depend upon the amount of milk and rennet used, the strength 

 of the rennet, the temperature and the ripeness of the milk. All except 

 the last remaining constant from day to day, the degree of ripeness is 

 measured by the time required for coagulation. The riper the milk the 

 shorter the time; ordinarily from one and one-half to two minutes will 

 be required. The diluted rennet must be made fresh every day. 



MABSCHALL RENNET TEST 



For a description and cut of this test, see page 242. Directions for 

 its use: To determine the ripeness of milk for cheese making, fill the 

 vessel to the mark with milk, add a pipette full of commercial ren- 

 net, stir quickly, and place in such a position that the milk may flow 

 freely from the orifice. When the milk ceases to flow, note the number 

 of graduations exposed. The riper the milk the less the number of 

 exposed graduations. 



HOT IRON TEST 



A test used to indicate the maturity of curd in cheese making. The 

 maturity is usually coincident with the amount of lactic acid present, 

 so that the test is commonly called the hot iron test for acid. 



The test is made by heating a bar of iron just short of redness, or 

 so that it will hiss readily. A mass of curd is squeezed in the hand till 

 ail the whey possible is pressed out. The curd is then applied to the 



