232 THE ANALYSIS OF CHEESE. 



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 weighing, 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 

 between the " total soluble extract," less ash of soluble 

 extract, 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 tire, 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 

 of the method of cheese analysis, of which the following is an 

 abstract : 



Ash and Mineral Matter. From 10 to 15 grammes of the 

 cheese are burnt (preferably in a muffle) in a platinum basin. 

 The weighed ash is dissolved in 250 c.c. of water and an aliquot 

 portion used for the determination of chlorine (calculated to 

 sodium chloride). The portion insoluble in water may also be 

 dissolved in dilute hydrochloric acid and made up to 250 c.c. ; 

 in a mixture of equal aliquot portions of each of these solutions 

 the calcium and phosphoric acid may be determined. 



Water. A weighed quantity of the cheese is mixed with 

 washed, ignited, and sifted quartz sand. For most cheeses the 

 proportion of 100 grammes to 400 grammes of sand is satis- 

 factory, but with very rich cheeses 500 grammes of sand are 

 taken. This sand mixture is used in all the estimations. For 

 the determination of the water, an amount of the mixture corre- 

 sponding to about 3 grammes of cheese is dried to constant 

 weight in the water-oven. 



