2o6 Report of the Chemical Department of the 



Table VII — Showing Effect of Heat on Proteolytic Enzymes in Milk. 



We have found that the percentage of sohible nitrogen in 

 nearly fresh milk is often as high as 10 per ct. of the nitrogen in 

 the milk. These results show that, during, the long period of 

 time indicated, no proteolysis had occurred and that we are 

 justified in saying the milk was enzyme-free after heating. 



effect of common salt on action of rennet in cheese- 

 ripening. 



In Bulletin No. 203, page 241, we gave results showing that 

 salt, in the proportion of about i per ct., the amount usually 

 present in cheese, exerts a rather marked repressing influence 

 upon the proteolytic action of those enzymes that are present in 

 miLl< when made into cheese. We have also found that, in normal 

 cheese, the addition of increased quantities of salt decreases the 

 rapidity of proteolytic action. Some of our experiments were 

 planned with a view to study the action of salt on cheese-ripening 

 when rennet-enzyme is the only proteolytic factor present. In 

 experiments 44 and 47, the results were negative because, in the 

 absence of acid, no ripening change of any kind occurred. In 

 experiments 45 and 46, the amount of soluble nitrogen was the 

 same with and without salt, but was rather small in both cases, 

 compared with normal cheese. In experiments 48 and 51, larger 

 amounts of soluble nitrogen compounds were formed in the 

 presence of salt. This may have been in part due to the fact 

 that cheese 48 contained much moisture and was kept at a little 

 higher temperature for the first few weeks. ■ In experiments 52 

 and 53, the formation of soluble nitrogen compounds was less 

 when salt was added; but, in these cases, we had present biological 



