160 SCIENCE AND PRACTICE OF DAIRYING. 



place in them, are, to a certain extent, much more easily and per- 

 fectly churned than when in a sweet condition, it must be concluded 

 that the forces which effect the union of the fatty globules increase 

 with the greater souring of the milk. When it is considered, how- 

 ever, that in souring, the condition of the different phosphates 

 which are present in milk is changed, and in consequence of this the 

 original chemical condition of the caseous matter, and the nature of 

 its source, is also changed, it would appear as if churning in every 

 respect succeeded best after the original condition of the caseous 

 matter had suffered, up to a certain degree, a change in its state of 

 tenuity. To effect this condition of the caseous matter is the chief 

 object of the process of souring, by which cream and milk are 

 prepared for churning. It has hitherto been impossible in churning 

 sweet milk to obtain even comparatively satisfactory results, and 

 it is for this reason that in treating milk for butter the milk is 

 nearly always treated in the sour condition. Sweet cream, if 

 properly treated, yields a satisfactory quantity of butter, although 

 less than sour cream. In practice the churning of sweet cream is 

 only carried out on a very limited scale. By far the largest pro- 

 portion of butter is made from sour cream. 



In churning, butter separates out in round greasy granules, 

 which on an average are 2 millimetres in diameter, that is to say, 

 about the size of the head of an ordinary pin. They float about in 

 the butter-milk, which is a bye-product of the churning. The little 

 masses which are formed by the union of the small granules may 

 be called raw butter, in distinction to the finished article, which is 

 formed by kneading and working up the raw butter. The weight of 

 raw butter and of butter- milk obtained together never represent 

 the whole weight of the milk or cream treated, but are always 

 5 to 1 per cent less. It is not possible to make into butter all the 

 fat present in the milk or cream, a small residue, amounting to 

 2 to 4 per cent of the entire mass of the fat originally present, 

 remaining behind in the butter-milk, according as to whether milk 

 or cream has been treated. The manufacture of butter from sour 

 milk, sour and sweet cream, will be discussed later on. 



83. Butter Churns. The first condition of every butter churn is 

 that, under proper treatment, thorough separation of raw butter 

 from the milk or cream should be effected without difficulty, in from 

 35 to 45 minutes. The more simple and perfect the arrangement of 

 the churn is for effecting this, the better the churn is. Experience 



