192 MARKET DAIRYING 
The sample cans are next placed in the insulated box 
provided for them. Here they are warmed by adding 
water at a temperature of 103° F. to the box, a tempera- 
ture which should be maintained throughout the whole 
test. 
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Fig. 49.—Section through curd test. 
With a sterile thermometer watch the rise in tempera- 
ture until it has reached 86° F. when 10 drops of rennet 
extract are added to each sample and mixed with it for a 
few moments with a sterile case knife. This knife must 
be sterilized for each sample to avoid transferring bacteria 
from one can to another. 
As soon as the milk has curdled it is sliced with the 
case knife to permit the separation of the whey. After 
the whey has been separating for half an hour, the sam- 
ples should be examined for flavor, which can be told far 
better at this stage than is possible by smelling of the milk 
as it arrives at the creamery. 
After the samples have all been carefully examined, 
the whey is poured off at intervals of from twenty to 
forty minutes for not less than eight hours. At the end 
