CHAPTER XXVIII. 



BUTTER, CHEESE, ETC. 



Butter. 



Definition. Butter is the substance produced by churning 

 milk or cream, during which process the fat globules coalesce 

 to form granules ; when freshly churned, butter has the appear- 

 ance of a fine granular mass ; but, after being worked, this 

 assumes a structure homogeneous to the naked eye. 



Action of Salt. The action of salt, which is added both to 

 give a flavour and as a preservative, seems to be as follows : It 

 first dissolves in the buttermilk left in the butter, and forms a 

 strong solution, which curdles the buttermilk, giving an insoluble 

 precipitate of protein matter and a clear whey. The salt solution 

 has a smaller viscosity than the buttermilk ; hence a smaller 

 layer is condensed round the particles by surface energy, and 

 there is liquid which is very loosely held in the butter ; this 

 gradually runs out, and gives rise to the wet appearance of salt 

 butter. It is noticed that the liquid which runs out, or is squeezed 

 out, of salt butter is always clear and transparent, while the 

 liquid squeezed out of fresh butter is usually milky. 



By warming to a temperature near the melting point of the 

 4at considerable quantities of water can be mixed with butter. 

 In the preparation of " pickled " butter advantage is taken of 

 this fact to add large amounts of salt by working in warm brine. 

 Butter treated in this way does not lose its water easily, as an 

 emulsion of fat and water is thus produced. 



Storch has shown that by the action of certain micro-organisms 

 such a condition (of the proteins ?) is produced, that large amounts 

 of water are retained and cannot be worked out. In this case 

 an emulsion is produced, which contains large numbers of very 

 minute water globules. These butters are designated " thick," 

 and are rare in England. 



Theory of Churning. Several theories have been put forward 

 to account for the phenomenon of churning. Thus, Fleisch- 

 mann holds the view that the globules of fat in milk are in a 

 superfused condition, and that churning is simply the phenom- 

 enon of solidification ; with the recognition of the fact that the 



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