NEUTRALIZATION OF SOUR CREAM 175 



cent excess lime added will tend to reduce the acidity of the 

 cream slightly below the calculated point, while in cream of 

 relatively low original acidity, the point to which the acidity 

 drops will tend to be slightly above the calculated point. 



Effect of Per Cent Casein in Cream on Accuracy of Acid 

 Reduction. Since the fact, that a portion of the lime does not 

 react, is due to the mechanical tying-up of a portion of the lime 

 with the casein, the amount of lime not reacting must of 

 necessity vary with the per cent casein in the cream, and this 

 in turn is largely controlled by the fat content of the cream. 

 Generally speaking, the ratio of solids not fat to water in cream 

 is the same as that in milk, hence the more fat, and therefore, 

 the less water cream contains, the lower is the per cent of solids 

 not fat in cream, and the per cent curd, being a non-fatty con- 

 stituent is also reduced correspondingly. The following Anal- 

 ysis of Cream, by Richmond, 1 illustrates this point clearly. 



Table 34. Composition of Cream, 



The above analysis shows that cream testing 56. per cent 

 fat contained only 1.57 per cent protein, while cream testing 3(7. 

 per cent fat contained 2.76 per cent protein. 



The smaller curd content of rich cream, therefore, ties up 

 less lime than the larger curd content of thin cream. In the 

 case of rich cream, the proportion of lime not reacting with the 

 lactic acid is less than in thin cream. Hence the acidity in rich 

 cream is reduced to a slightly lower point than that in thin 

 cream, when the calculated amount of lime used is the same 

 for both, rich and thin cream. 



1 Richmond Dairy Chemistry, Second Edition, 1914, p. 266. 



