11 



fat) separate out immediately below the fat tlie test must be 

 repeated. To get a correct reading in the case of separated 

 milk or butter-milk is much more tedious than in the case of 

 whole milk. 



CREAM TESTING. 



The estimation of fat in cream presents exceptional diffi- 

 culties, and is liable to more serious errors than milk testing, 

 and no one who is not an adept in the use of delicate measuring 

 apparatus can be relied upon to determine the value of cream. 

 With great care, and duplicate testing, however, the amount of 

 fat in cream may be determined with an accuracy sufficient for 

 commercial purposes, and this, too, by the Gerber method. 



What has been said with regard to the need for care in the 

 testing of milk applies with equal force to the testing of cream. 



The method consists in carefully diluting 11 c.c. of the 

 cream so that it may be tested as if it were ordinary milk, and 

 afterwards making the proper allowance for the degree of dilu- 

 tion. Still another method whereby the cream is actually 

 weighed might be adopted ; but this requires the use of a deli- 

 cate balance with which creamery managers are not often sup- 

 plied. Anyone, however, who has such a balance, who has been 

 thoroughly trained in its use, and who wishes to employ this 

 method, may obtain the necessary apparatus and full instruc- 

 tions from any agent supplying the Gerber tester. 



The peculiarity in the case of cream which gives rise to most 

 of the difficulty in testing is its viscosity, a property which 

 greatly favours the retention of air bubbles. Accordingly, be- 

 fore cream can be tested with accuracy it must stand at least 

 two hours after separation, so that the excessively fine air 

 bubbles, often so fine as to escape the eye, may have had time 

 to escape from the mass. Cream from an auxiliary should be 

 thoroughly mixed, before the sample is taken, and should not 

 contain more than ,* 2 per cent of acid. 



Before taking the quantity requisite for a test the sample, 

 which should have stood for at least half an hour, 

 must be thoroughly mixed, and to do so it should be first 

 warmed, if necessary, to 20 C., and then carefully stirred with 

 a spoon. In dealing with very viscous cream it may be neces- 

 sary, first, to warm it to 50 C., and afterwards to cool down 

 to about 20 C., before taking the sample. On no account 

 should the sample be shaken or air bubbles will be in- 

 cluded. When properly mixed, take the test sample with a 

 dry pipette which has been certified accurate. Draw the 

 cream slowly into the pipette and only slightly above the 

 mark. Before adjusting the liquid to the mark carefully wipe 



