226 



VEGETABLE ENZYMES, XVIII 



TABLE V. 



Actions of Yeast Sucrose on Boiled, Filtered, Potato Juice Solutions. 



the juices as prepared. The two results in parentheses are probably- 

 incorrect. 



The results, compared with the results on sucrose, show that the 

 two sets of actions are similar. Optimum actions were obtained 

 over approximately the same range of acidity. This proves that 

 sucrose (or rafiinose) is present in the juice, and that its concentra- 

 tion is of the order of magnitude of 1 per cent.^^ 



CONCLUSIONS. 



From the actions observed with potato juice alone and in the pres- 

 ence of added starch, it is now possible to state definite conclusions. 

 The marked actions at pH 4 to 5 of the juice alone and also in the 

 presence of the added starch were due to the hydrolysis of sucrose 

 (or rafhnose) by the sucrase of the juice. There was very Httle action 

 upon the starch of the juice itself or upon added starch. At pH 6, 

 the action observed in the juice alone was made up of the action of 

 the sucrase and of the amylase, both on the constituents of the juice; 

 additional action v/as observed on the added starch. At pH 7 to 8, 

 there was little action of the sucrase, only that of the amylase being 

 observable. 



The amylase had an optimum pH of 6 to 7 and acted in the same 

 way upon both the starch occurring in the juice and upon the added 



^^Konig, J., Chemie der menschlichen Nahrungs- und Genussmittel, Berlin, 

 4th edition, 1904, 895, 897. 



