380 OTHER MILK PRODUCTS. 



order to compare the method given above with that previously 

 described. 



For most practical purposes the author's method will give as 

 much information as that of Stutzer, if the following facts are 

 borne in mind : — (1) The ripening of a cheese is shown by the 

 proportion of primary and especially secondary products ; and 

 (2) the digestibility of a cheese increases with its ripeness. 



Duclaux's Method. — Duclaux has proposed the investigation 

 of the fatty acids developed by ripening as a means of judging 

 a cheese. The following are the methods used by him : — 



Water, Fat, Alcoholic and Aqueous Extracts. — Twenty 

 grammes of sand which has been previously dried, sifted, and 

 ignited, are' weighed out, and about seven-eighths are placed in 

 an enamelled mortar ; 2 to 3 grammes of cheese, accurately 

 weighed, are ground up with the sand to form a homogeneous 

 mass, which should become nearly pulverulent. The mixture is 

 introduced into a small calcium chloride tube, fitted with a plug 

 of asbestos to prevent loss, and the basin rinsed out with the 

 remainder of the sand. The tube with its contents are weighed, 

 and placed in a bath heated to 50° or 60°, and a current of dry 

 air passed through for some hours. After cooling, the tube is 

 weighed and the loss noted as water. 



The fat is now extracted by carbon bisulphide (other solvents, 

 such as ether or chloroform, may be used), the tube again dried 

 and weighed, and the amount of fat deduced by difference. 



The tube may be similarly exhausted by alcohol, hot or cold 

 water, and the loss of weight noted after each extraction. 



Ash. and Salt. — A fresh portion of cheese is weighed out into 

 a platinum basin, and ignited to obtain the ash ; in this, the 

 chlorine is titrated with standard silver nitrate, using potassium 

 chromate as indicator. 



Proteins and Products of Ripening. — About 10 grammes 

 of cheese are weighed and intimately mixed in a mortar with 

 about 10 c.c. of water ; a very homogeneous paste is formed, and 

 this is left for half an hour to ensure the perfect contact of the 

 water with the solid matter. More water is added, little by 

 little, the mixing in the mortar being continued till 100 c.c. have 

 been added. The mixture is now filtered through a porous 

 porcelain filter by means of reduced pressure ; in several hours 

 60 to 70 c.c. can be obtained. 



Ten c.c. are evaporated in a platinum basin, the residue dried 

 at 100°, weighed, then ignited, and the ash weighed. The 

 diif erence will give the organic matter ; this is termed by Duc- 

 laux " caseone," and represents the products of ripening. The 

 percentage may be calculated with approximate accuracy, by 

 multiplying by 100 -|- the weight of water in the amount of 



