in CHEESE 191 



B. DETECTION OF ADULTERATION. 



Cheese is not infrequently adulterated by replacing the fat 

 in the milk from which the cheese is made by other less 

 valuable fats in the form of an emulsion. If, therefore, the fat 

 of a cheese has to be more closely investigated, the first thing 

 is to obtain a considerable quantity of it. The best way to 

 achieve this is by the method described by H. Brehmer. 1 



One hundred grams of finely divided cheese are ground in a 

 mortar with acidulated water (five parts dilute sulphuric acid to 

 200 parts water) at a temperature of 20-30 C., the water being 

 added gradually. The emulsion is then centrifuged, and the 

 fat which separates is kneaded with a little water, and then 

 melted at a moderately low temperature. After filtration 

 through a dry filter it is then ready for use. The methods 

 used in investigating the fat are naturally the same as those 

 which have been described for butter-fat. 



It is possible to extract the fat from the cheese by simply 

 warming it in a drying oven at about 80 C., but there is 

 always the danger that if the temperature rises above this 

 point the fat begins to decompose. As regards the margarine 

 test in the case of the fat of cheese, the method described on 

 page 167 is followed exactly. As, however, the prescribed 

 addition of sesame oil in the case of margarine cheese is only 

 5 per cent., more of the fat, 10 c.c., should be taken for the 

 test. 



C. TESTING OF RENNET. 



Rennet is the enzyme extracted from the mucous membrane 

 of the stomach of mammals, and small amounts of it have the 

 power of curdling or coagulating large quantities of milk. 

 This process of coagulation only takes place within a certain 

 range of temperature, the most suitable point being slightly 

 above 40 C. This enzyme (scientifically named chymosin) is 

 found in large quantities in the stomachs of young animals 

 living solely upon milk, and a typical case is that of the calf. 

 From the earliest times man has obtained the rennet which he 

 has used in the making of cheese from milk, by extracting 



1 Forschnnytbericht ilber Lebensmittel, u.s.w., 1897, p. 51. 



