COMPOSITION OF CREAM. 



419 



Qualitatively, it has the same composition as milk ; quantita- 

 tively, it contains a higher proportion of fat, the other consti- 

 tuents being correspondingly depressed. 



It is by many accepted as a fact that cream contains a larger 

 proportion of solids not fat to water than the milk from which 

 it was derived ; and various explanations of this have been put 

 forward. Thus a membrane round each fat globule has been 

 alleged to exist by some (e.g., Storch and Bechamp) ; others have 

 considered that the proteins are concentrated in the aqueous 

 layer formed round each globule by surface tension. The author's 

 experiments have indicated that the ratio of solids not fat to 

 water in cream is the same as that in milk, and Weibull and 

 Smith and Leonard have confirmed this conclusion. It is true 

 that in some cases a distinctly higher ratio has been found, but 

 it has been noticed that in these cases ample opportunity for 

 evaporation of the water has been afforded, either by leaving the 

 cream on the surface of the milk for some length of time in a 

 dry atmosphere, or by pasteurising it, without any precautions 

 to prevent evaporation ; indeed, evidence of evaporation has 

 been obtained by noting the quantity of cream before and after 

 pasteurising. In cases where precautions have been taken to 

 prevent evaporation, no evidence of a higher ratio has been 

 obtained. 



In the following analyses (Table CXLV.) the solids not fat 

 have been calculated by dividing the percentage of water by 

 100 and multiplying by 10-2 (except in No. 2 where 10-0, and 

 No. 9 where 10-4 has been used), this being the average ratio 

 in the milk from which these creams were prepared. The calcu- 

 lated ash is T T of the calculated solids not fat : 



TABLE CXLV. COMPOSITION OP CREAM. 



In cream No. 1 the proteins were also estimated, and found 

 to be 2-60 per cent., while the figure calculated on the assumption 



