CHAPTEr. XII. 



CHEESK. 



Cheese consists mainly of caseine, milk-fat, a little salt and 

 phosphate of lime, and water. It is, as is well known, pre- 

 pared by subjecting milk to tbe action of rennet, which, 

 coagulates it, and then pressing the curds, which, after 

 treatment, constitute the cheese. There is gieat variation in 

 the composition of cheese. 



According to Payen, the water ranges from 30 to 62 per 

 cent. ; the fat, according to the same chemist, appears to vary 

 from about 20 to about 30 per cent. The percentage of 

 caseine appears to range from 15 to 85, and the mineral 

 matter from 4^ to 7. 



The analysis of cheese is managed as follows : — The water 

 is determined by taking about one gramme, and drying it in 

 the water-bath in a small platinum dish (one of the little 

 dishes used for milk-residues will answer very well), until it 

 ceases to lose in weight. After the determination of the 

 water, the residue may be ignited, and the ash weighed. 



For the determination of fat and caseine, it is well to take 

 a larger quantity of cheese. About ten grammes is a con- 

 venient quantity. The cheese should be weighed out, having 

 been first cut up into small pieces, and then introduced into a 

 small flask. It is then boiled with dry ether, and the resulting 

 ethereal solution of the fat is decanted off ; the boiling and 

 decantation is repeated twice, and, finally, the ethereal solu- 

 tions are carefully evaporated down in a platinum dish, and 

 the fat which is left behind is dried at 100" C. and weighed. 



