168 NEUTRALIZATION OF SOUR CREAM 



.193 per cent, the per cent reduction of acid in the curd still 

 exceeded that in the serum, though to a lesser extent than when 

 neutralization was carried only to .26% acid in the cream. The 

 same tendency would obviously occur in the case of cream of 

 very high acidity. It can readily be seen that while the lactic 

 acid in the cream can be increased very greatly, the per cent curd 

 and therefore, the amount of acid it contains is quite constant 

 and remains practically the same. Hence in the neutralization 

 of high-acid cream, the per cent reduction of the lactic acid in 

 the serum might be greater than that in the curd. In very high 

 acid cream, it might be possible for the acid in the curd to be 

 reduced to the neutral point. This is improbable, however, 

 because in such cream the stronger acid (the lactic acid of the 

 serum) would claim more of the alkalinity of the lime. 



It should be noted also in Table 30, that the per cent reduc- 

 tion of the acid in the fat is very slight. This may be explained 

 by the probability that the fat becomes saturated with lactic 

 acid from the acid serum and the acid so held is not redistributed 

 in the serum, unless the serum is reduced to a low percentage 

 of acid. This assumption' is borne out in the case of Sample 

 No. 3, representing cream neutralized to .193 per cent acid and 

 in which the acid reduction in the fat was abnormally great. 



Ability of Acid Test with Sodium Hydroxide to Show Total 

 Acidity in Cream. It has been shown that the lime has a great 

 affinity for the casein, that the curd of neutralized cream absorbs 

 over five times as much calcium as the serum and that the action 

 of the lime on the acid in the curd is in excess of that on the 

 lactic acid in the serum. The question then arises, does Sodium 

 which is used in testing the cream for acid, and in the use of 

 which the titration is carried to the neutral point, show a similar 

 preference for the acid in the curd as the lime? In other words, 

 does the acid test "show the total acid in the cream, including 

 both the lactic acid and the casein acid, or does it indicate the 

 lactic acid only? 



This question is important, because if the acid test rep- 

 resented the determination of the lactic acid only, then it would 

 not be a true index of the acidity of the cream and it would also 

 furnish a very logical explanation of why a portion of the lime 



