DIFFERENT NITROGENOUS COMPOUNDS 209 



show a greater activity in rennet cheeses than in the case of 

 cheeses produced from the curd precipitated by acids. Cheeses of 

 the latter type are practically unknown in this country. 



199. Determination of Total Nitrogen. 



The percentage of total nitrogen present in cheese 

 is determined by Kjeldahl's process (p. 10), using 

 3 to 4 grams of cheese. 



200. Determination of the Total Soluble 



Nitrogenous Compounds. 

 Ten grams of cheese are rubbed to a paste with 

 warm water, and the liquid transferred to a 250 c.c. 

 standard flask, which is then filled up to the mark. 

 The flask and its contents are allowed to stand for 

 some hours, and the liquid is then filtered through a 

 dry filter. Fifty c.c. of the clear filtrate are withdrawn 

 by means of a pipette, transferred to a Kjeldahl flask, 

 evaporated to dryness, 20 c.c. concentrated sulphuric 

 added, and the nitrogen estimated by Kjeldahl's process. 

 The soluble proteins are estimated in another portion 

 of the original filtrate as follows : — 



201. Determination of Soluble Protein Nitrogen. 

 Fifty c.c. of the clear filtrate containing the water- 

 soluble constituents of cheese are acidified with dilute 

 HgSO^.and 20 c.c. of a 10 per cent, solution of phospho- 

 tungstic acid added. 



The precipitated proteins are filtered off, well 

 washed with water, and the nitrogen estimated by 

 Kjeldahl's process, the result being given as nitrogen 

 in the form of water-soluble proteins. 



202. Determination of Ammoniacal Nitrogen, 



One hundred c.c. of the clear filtrate containing 

 the water-soluble constituents of cheese are placed in 



o 



