Enzyms of Apples 



occurrence, there being always the possibility that observed changes in 

 the nature of the sugars present in successive samples may be due to the 

 action of organic acids during the preparation of the samples for analysis. 



TANNASE 



Determinations of the tannin content of each of the four varieties of 

 apples which were being used by Proctor's modification of Lowenthal's 

 method ' showed that the flesh of the apples contained the following per- 

 centages of tannin : Rome Beauty, 0.208 ; Arkansas Black, o. 192 ; Yellow 

 Newtown Pippin, 0.208; King David, 0.132. 



It seemed advisable to ascertain, therefore, whether any tannin- 

 hydrolyzing enzym was present in these tissues. Accordingly, a quantity 

 of pulp from each variety was ground with quartz sand and the juice 

 expressed. One portion of the juice from each variety was boiled and 

 another left unboiled. Aliquots of the boiled and unboiled juice were 

 placed in each of two test tubes, to one of which 2 c. c. of a 10 per cent 

 solution of Merck's tannic acid was added, in order to insure sufficient 

 excess of substrate material. The four sets of four tubes each were placed 

 in an incubator at 40° C. for 24 hours. At the end of this time a few drops 

 of a 10 per cent solution of ferric chlorid were added to each test tube 

 and the intensity of color developed in the tubes containing check boiled 

 and unboiled juices was compared. In no case could the slightest 

 difference in intensity of color be observed, from which it was concluded 

 that the juices contained no tannase. 



EMULSIN 



Glucoside-spHtting enzyms were tested for in boiled and unboiled 

 juices prepared from each of the four varieties of apples by digesting 

 aliquots of these juices with 2 c. c. of a i per cent solution of amygdalin for 

 24 hours at 40° C. In no case was any odor of benzaldehyde perceptible 

 at the end of this time, while check tubes to which emulsin was added 

 gave a pronounced odor after only 10 minutes' contact with the amyg- 

 dalin used. Hence, it was concluded that the apple flesh contains no 

 enzym of the emulsin type. 



ESTERASES 



One of the noticeable changes in an apple during the ripening period 

 is the development of its characteristic odor and flavor, due chiefly to 

 the ester ethyl malonate. Such esters are usually accompanied in nature 

 by a corresponding esterase; hence, it seemed advisable to test the flesh 

 of the apples for an esterase which would hydrolyze ethyl malonate. 



Accordingly, apple juice was obtained by the quartz-sand method and 

 a series of test tubes prepared with the following contents: (i) 5 c.c. 

 of apple juice, 5 c. c. of ethyl malonate, and 10 c. c. of distilled water; (2) 

 5 c. c. of apple juice which had been previously boiled for 10 minutes, 



' Wiley, H. W., et al. Official and provisional methods of analysis, Association of Official Agricultural 

 Chemists. U. S. Dept. Agr. Bur. Chem. Bui. 107 (rev), 272 p. 1908. See p. 150. 



