234 MILK AND DAIRY PRODUCTS PART 



sample of cheese are treated with 200 c.c. of boiled water and a 

 few c.c. of sulphuric acid, and then distilled with steam. Just 

 as in the case of milk, the steam must be passed into the flask 

 before the direct heating begins, so as to prevent the contents 

 from burning. The distillation is carried on until a litre of 

 distillate has been collected, and this is titrated with baryta 

 water, evaporated, and treated, as on p. 220. 



3 Acid Number of Cheese Fat. 



The acid number of cheese fat is the number of cubic 

 centimetres of standard alkali which are needed to neutralise 

 100 g of fat. 



In order to separate the fat, 1 the cheese is heated in the 

 same way as in the estimation of fat by the Schmid-Bondzynski 

 method (p. 187), that is, with hydrochloric acid (sp. gr. I'l), in a 

 boiling water-bath until the protein dissolves completely. After 

 the burner has been taken from under the water-bath, the 

 beaker is allowed to remain for half an hour to permit the fat 

 to collect on the surface of the liquid. After this, the beaker 

 is cooled in ice-water and the solid cake of fat subsequently 

 washed with cold water. This cake of acids is then melted 

 with water, and again allowed to cool. The melting and 

 freezing of the solid acids is continued until the wash-water 

 shows no trace of hydrochloric acid. Finally, the cake of fat is 

 dried between filter-paper, dried, melted, and filtered. 2 



The degree of acid of the fat obtained by the hydrochloric 

 acid method serves as a measure of the decomposition which 

 the fat has undergone in the cheese. 3 



4 Nitrogenous Substances. 



In order to get a general idea of the degree of decomposition 

 of paracasein in cheese, it is generally sufficient to determine 

 the total nitrogen, the soluble nitrogen, and the ammoniacal 

 nitrogen. The best way of making these analyses has already 



1 K. Windisch, " Uber Margarine Kase," Arbeiten aus dem Kaiserlichen 

 Gesimdheitsamte, Berlin, 1898, p. 554. 



2 If it is not possible to get a solid cake of fat, then the fat can be shaken 

 out with ether. _Hi* 



3 Orla Jensen, Landwirtschaftliches Jahrbuch der Schwtiz, 1904, p. 326. 



