ANALYSIS OF CHEESE. 375 



and the heating and shaking continued till solution is efEected. 

 The solution is cooled, 25 c.c. of ether are added, and the contents 

 of the tube mixed, and 25 c.c. of petroleum ether poured in, 

 the solutions mixed, and the fat estimated in the usual manner. 



Proteins and the Products of Ripening. — About 10 

 grammes of cheese are well ground up in a mortar with ten 

 successive portions of 20 c.c. each of hot water, the aqueous 

 portions being poured ofE into a 250 c.c. flask. The grinding 

 should be as thorough as possible, every lump of cheese being 

 well crushed. After cooling, the solution should be made up to 

 250 c.c. and filtered. 



Twenty-five c.c. of the filtrate should be evaporated in a 

 platinum basin on the water-bath, and the residue dried in the 

 water-oven to constant weight. This may be termed the 

 " total soluble extract." The residue may be incinerated at 

 a low red heat, and the ash of the soluble extract weighed. 



Twenty-five c.c. of the filtrate are diluted to about lOO c.c, 

 5 c.c. of a solution of copper sulphate solution added (34 "64 

 grammes to 500 c.c), and caustic soda solution added, drop by 

 drop, till the precipitate settles in the form of curd, and leaves 

 the supernatant liquid quite clear. After standing for some time, 

 the precipitate is collected on a Gooch crucible, washed with 

 water, and dried at 120° C. After weighiiii;, the crucible is 

 ignited, and the residue of copper oxide and phosphate weighed. 

 The difference between the two weights may be taken as " primary 

 products of ripening." The difference between this figure and 

 that of the " total soluble extract," less the ash, may be taken 

 as " secondary products of ripening." The difference Ijetween 

 the " total soluble extract," less ash of soluble extraet, and 

 the " solids not fat," less total ash, may be taken as proteins. 



The above method will be found to be fairly rapid and to give 

 an insight into the composition of the protein matter of the 

 cheese. The separations between the different classes of protein 

 substances are, however, arbitrary. Thus it is assumed that all 

 the insoluble " solids not fat " consist of protein, and that all the 

 products of ripening (and nothing else) are soluble. The dis- 

 tinction between primary and secondary products of ripening is 

 based on the assumption that primary products are precipitated 

 as basic copper compounds, while secondary products give soluble 

 compounds under the conditions given above. In the present 

 state of knowledge it is impossible to identify and separate all 

 the products of ripening ; therefore empirical methods which 

 yield comparative results are necessary. 



Stutzer's Method. — If it be desired to obtain further infor- 

 mation, the method given above may be elaborated by some 

 of the methods detailed below. Stutzer has published a study 



