84 DAIRY ANALYSIS 



portions have been used ; cool the total filtrates, make 

 up to 250 c.c. and mix well. Evaporate 50 c.c. in a 

 weighed basin, and weigh the solids after drying till 

 the loss is less than i milligramme per hour ; ignite, and 

 weigh the ash ; the weight of the solids less that of the 

 ash represents the products of ripening. The difference 

 between 100, and the sum of the water, fat, ash, and 

 products of ripening, may be taken as unaltered para- 

 casein. 



Ths products of ripening may be differentiated ; to 

 50 c.c. of the filtrate add 5 c.c. of copper sulphate, and 

 treat as in the Ritthausen method for the estimation of 

 proteins (p. 34) ; the proteins estimated in this way 

 may be termed primary products of ripening, and the 

 remainder secondary products. 



Examination of the Fat. Dry 25 to 50 grammes 

 of cheese till the fat runs out ; extract with ether, 

 and wash the ethereal solution with water in a 

 separating funnel ; remove the ethereal layer, and 

 drive off the ether, and dry the fat till the ether is 

 completely removed. Examine the fat as directed for 

 butter fat ; usually a Reichert-Wollny figure is 

 required. 



The Application of Analysis to the Solution of 

 Problems. Detection of Adulteration. Practically the 

 only adulterations of cheese consist in the removal of 

 fat from the milk before curdling, and the addition 

 of foreign matter. 



The removal of fat may be judged if the fat is less 

 than 45 per cent, of the dried cheese, or if the fat is 

 less than six times the total nitrogen, both of which 

 standards lead to practically the same result ; a large 

 number of cheeses are made with half-skimmed milk 

 (e.g. the evening's milk is skimmed, and mixed with the 

 fresh morning's milk) ; these fail to comply with the 

 above standards, and should be sold as half-skim 

 cheeses ; other cheeses are made from skim-milk alone, 

 e.g. Dutch cheese (though cheeses are made in Holland 

 with whole milk also). 



