RENOVATED BUTTER 273 



hollow-bowl, Danish- Weston separator, and the recovered 

 oil added to the main batch. 



Refining the Oil. — This clear oil is run into a second set 

 of tanks, or kettles, kept at a constant temperature of 

 about 120° F. for several hours. During this time, pure, 

 hot air is continuously pumped through the fat. The air is 

 conducted to the bottom of the kettle through a pipe ex- 

 tending through the oil from the top. This air rises and 

 causes a constant ebullition of the oil. This aeration at a 

 high temperature removes practically all the bad odors and 

 fla\'ors, and leaves an almost tasteless, clear, }-eUow oU. 



Making the Emulsion. — This oil is emulsified with sour 

 milk, in order to reincorporate into it a natural butter 

 flavor and the components of normal butter. For this 

 purpose a quantity of good fresh skim milk is ripened with 

 a commercial ciilture of lactic-acid bacteria, just as a starter 

 is made in a butter or cheese factory. To this sour milk 

 is added about twice its volume of sweet skim milk; then 

 this mixed milk is added to the molten oil in the ratio of 

 about one part milk to one and one-half parts oil. The 

 milk and oil are mixed and emulsified in a c}'lindrical tank 

 or kettle in which there is a rapidly revolving dasher. In 

 some factories the emulsion is made in the same kettle 

 in which the renovating process occurred. The mixing is 

 accompHshed b}' passing air through the mixture. 



Crystallizing the Fat. — This emulsion is then run into a 

 large vat of water at a temperature of 36° to 46° F., which 

 crystallizes the fat. Even though such a large percentage 

 of milk is present it is all incorporated in the fat crystals. 

 The water shows no trace of milkiness. 



The crystaUizing vat is usually placed directly under- 

 neath the bottom of the renovating or mixing kettle. This 

 latter tapers at the bottom to a small mouth. A valve at 



