168 WASHING AND WORKING OF BUTTER. 



chums is equal in quality to that produced in the or- 

 dinary time, farmers had better beware how they 

 change their method, lest the quality of their butter, 

 and consequently the reputation of their dairy, be 

 injured. 



Butter contains two kinds of fat. If melted in wa- 

 ter at about 180 F., a nearly colorless oil is obtained, 

 which becomes solid on cooling. If the solid mass be 

 subjected to pressure in a strong press, at about 60 F., 

 a pure liquid oil runs out, and there remains a solid 

 white fat. The liquid fat is called elaine, and the 

 solid fat, margarine. These two bodies are present in 

 many other animal and vegetable oils and fats. They 

 are both nearly tasteless, and, when quite pure, will 

 keep without change for a long time. In presence of 

 certain impurities, however, they do change. 



If great care is not taken in washing and working, 

 "when making butter, some buttermilk is left enclosed 

 in it; the buttermilk, of course, contains casein, the 

 nitrogenous body which we have already described; 

 there is also some of the milk sugar mentioned in sec- 

 tion I. The casein, like all other bodies containing 

 much nitrogen, is very liable to decomposition. This 

 soon ensues therefore, whenever it is contained in but- 

 ter; and certain chemical transformations are by this 

 means soon commenced, whereby the margarine and 

 elaine are in part changed to other and very disagree- 

 able substances; those which give the rancid taste 

 and smell, to bad butter. The milk sugar is instru- 

 mental in bringing about these changes. It is de- 

 composed into an acid by the action of the casein, and 

 has a decided effect upon the fatty substances of but- 

 ter, causing them to become rancid. This action and 

 consequent change comes on more or less rapidly, as 

 the temperature is warmer or colder. 



No matter how well the butter is made in othei re- 

 spects: if buttermilk be left in it, there is always, from 



