362 FOOD AND NUTRITION 



bottles and carefully fill them with boiling water until the liquid 

 comes up near the top of the neck of the bottle. Be careful to 

 avoid pouring in so much water that the fat runs out of the bottle. 

 Return the bottles to the machine and whirl them for one minute 

 more at the same rate as indicated above. By this process, the fat 

 is all thrown into the graduated neck of the bottle where its amount 

 may be read. (7) Read the upper and the lower limits of fat column 

 in the neck of the bottles. Subtract the smaller reading from the 

 larger one. The difference is the percentage of fat in the milk. 

 Repeat the operation with the other bottle. Do the two percent- 

 ages of fat agree? 



PROBLEM 



How many pounds of butter could be made from 100 Ib. of the milk 

 tested, provided the butter is to contain 85 per cent, fat, 13 per cent, 

 water, and 2 per cent, salt? 



If possible, test for fat by the Babcock method to see how com- 

 pletely the fat has been removed, milk that has been skimmed by hand. 

 Also test milk that has been separated by means of a cream separator 

 (see Arts. 617-621). For accurate work on the latter kind of milk, 

 a skim-milk bottle should be used. 



402. Butter. When cream is allowed to "ripen" (Arts. 446 

 and 624) and is then agitated in a churn the fat gathers 

 together in masses known as BUTTER. These masses of butter 

 are gathered together, washed with water, worked to remove 

 the excess of water, and then salted to impart an agreeable 

 flavor. Churning is most quickly accomplished by having the 

 temperature of the cream about 65 or 70F., but more solid 

 butter, and butter of better grain or texture is obtained by 

 churning at a lower temperature. The composition of butter 

 is shown in Table XIV. According to a standard established 

 by Congress, butter for interstate traffic must not contain 

 more than 16 per cent, of water nor less than 82.5 per cent, of 

 fat (see Fig. 249). 



403. Renovated or Process Butter. Through careless 

 methods of handling milk and cream and carelessness in manu- 

 facturing butter, it sometimes happens that the butter is of 

 inferior grade. Moreover, it may be held so long that it has 

 become rancid and unfit for food. Such butter is renovated 



