1 86 MILK AND DAIRY PRODUCTS PART 



has been placed a layer of sand, 1 cm. high, and a short glass 

 rod is carefully dried and weighed, and then a little of 

 the ground cheese is placed on the sand, weighed, heated to 

 melting point on the water-bath and well stirred up with the 

 sand. The subsequent treatment is the same as with hard 

 cheese. 



II. DETERMINATION OF FAT. 



a. Scientific Methods. 

 1. The Extraction Method. 



About 5 g. of cheese, if the sample is rich in fat, otherwise 

 10 g., are weighed out and brought into a porcelain mortar 

 containing about an equal quantity of fine ignited sand, and the 

 whole then dried in the manner described above. After 

 drying, the contents of the mortar are brought into a fat-free 

 extraction cartridge, which is placed in a Soxhlet extraction 

 apparatus. The mortar is then washed out several times with 

 ether, which is poured over the cartridge in the extractor, and 

 the extraction carried out in the usual way for several hours. 

 When the extraction has been going for about 2 or 3 hours it is 

 interrupted, and the cartridge taken out, and the contents ground 

 in a mortar. The extraction is then continued and followed 

 after a few hours by a further grinding up until the extraction 

 flask after evaporation of the ether shows no increase in 

 weight. 



This method is tedious and takes a long time ; it is also only 

 suitable for whole milk cheeses, or such cheeses as contain 

 a fair quantity of fat. With the poorer cheeses, and particularly 

 with skim milk cheese, the results are far too low. This 

 is partly due to the inability of the ether to reach the small 

 fat globules which are embedded in the dry cheese, and 

 probably also to a cause pointed out by Orla Jensen, namely, 

 that some of the free fatty acids of the cheese are present 

 as ammonia salts and so escape extraction by the ether. It is 

 therefore preferable, and for skim milk cheese essential, to 

 make use of one of the methods now to be described. 



