GENERAL REMARKS ON BUTTER-MAKING. 159 



kilo, of skim-milk will be \ 6 -/ = 6 pfennig. A kilo, of skim-milk could be 

 sold at 6 pfennig, which would cover the expense which had, up to that 

 time, been incurred in the production of the skim-milk in the dairy. 



In towns, skim-milk possesses a value which is practically half that of 

 the same volume of whole-milk. A kilo, of lean ox-flesh contains 18 per 

 cent of protein and 5 per cent of fat, that is, in 100 kilos, there are 23 

 kilos, of valuable constituents. If the nutritive value of protein and fat are 

 reckoned as equal, and if no account be taken of the value of the remaining 

 constituents of the meat, and that the cost of 100 kilos, of ox-flesh is 100 

 marks, therefore the price of a kilo, of protein or fat equals yy ) = 4'35 

 marks. 



If 100 kilos, of skim-milk contain 4 kilos, of protein and 4 -5 kilos, of 

 milk-sugar, and this latter only worth a fifth part of a kilo, of protein, there 

 is in the skim-milk altogether 4 '9 kilos, of constituents of the value of the 

 protein. Leaving out of consideration, as of no value, the fat contained in 

 the skim-milk, if 100 kilos, of skim-milk cost seven marks, the value of 

 a kilo, of protein is ~ = 1'43 marks. From this it will be seen that a kilo, 

 of protein in lean ox-meat is three times dearer than in the skim-milk. 

 Skim-milk, therefore, cannot be too strongly recommended as one of the 

 cheapest and most serviceable of foods. 



82. General Remarks on Butter-making. Butter consists, as has 

 already been pointed out in 4, practically of the fat which is 

 originally present in the milk in the form of countless extraor- 

 dinarily small globules. The collecting and uniting together of 

 the largest possible amount of these fatty globules is effected most 

 thoroughly by shaking and beating the fluid which contains the 

 fatty globules that is, churning for a time, in vessels specially 

 constructed for this purpose, viz. butter-churns. The butter may 

 be directly obtained from the milk as milk butter. By far the 

 greatest part of the butter, however, which is in daily use, is cream 

 butter. We have already seen in 6 that all, or at any rate the 

 larger number of the fatty globules, present in milk or cream at 

 ordinary temperatures, are in the fluid condition. Since butter is 

 separated out as a solid body, it follows that the milk-fat is con- 

 verted from the fluid to the solid condition by the shaking which it 

 undergoes while churning. We further know that the fatty globules 

 are surrounded with milk-serum, and that, owing to the molecular 

 strain caused in this way on their surface, they are very difficult to 

 bring into direct contact with each other. Since it has been found 

 from experience that milk and cream, as soon as souring has taken 



