io8 Journal of Agricultural Research ^ voi.v.Nas 



(6) A quantity of concentrated apple juice prepared by Gore (6) by 

 his freezing method was secured and used in some of the tests, since 

 it was thought that this process would be Hkely to leave the enzyms 

 uninjured in the juice. 



EXAMINATION OF DIFFERENT PREPARATIONS FOR ENZYMS 



In the earlier examinations reported below, several different prepara- 

 tions were examined simultaneously for the particular type of enzym 

 which was being sought, in order to avoid any wrong conclusion from 

 improperly prepared material. Experience soon showed, however, that 

 either the acetone-dried powder or the pulp ground with quartz sand 

 would yield active extracts in every case where activity could be found 

 in material prepared by any of the above methods, and one or the other 

 of these two preparations was used in all the later tests. The acetone- 

 dried powder has the advantage that a considerable quantity of material 

 can be prepared at one time for subsequent examination. 



DIASTASES 



Diastases have been shown by Thatcher and Koch (ii) to be readily 

 dififusible into water surrounding cell tissues. It seemed probable, there- 

 fore, that if enzyms of this type were present in apple flesh they would 

 appear in juice expressed from pulp after thorough rasping. Samples 

 of clear juice by decantation were secured from three different varieties 

 of apples and tested for diastatic activity. Four separate mixtures 

 were prepared for each variety of juice. The first contained lo c. c. of 

 a ID per cent solution of soluble starch prepared by the Lintner method 

 (5), lo c. c. of the juice in question, and 10 c. c. of distilled water. The 

 second contained 10 c. c. of soluble starch, 10 c. c. of the juice which had 

 been boiled for 10 minutes and made to its original volume with water, 

 and 10 c. c. of distilled water. The third contained 10 c. c. of soluble 

 starch, 10 c. c. of the unboiled juice, sufficient Njio sodium hydroxid 

 (NaOH) to exactly neutralize the juice used (determined by a preliminary 

 titration, using phenolphthalein as indicator), and enough distilled water 

 to make the total volume 30 c. c. The fourth, or control, contained i o c. c. 

 of soluble starch and 20 c. c. of distilled water. The contents of each flask 

 were thoroughly mixed and an aliquot drawn off for the determination 

 of reducing sugars present in the solution. The flasks containing the 

 remainder of the solution were then placed in an incubator for 30 min- 

 utes at 40° C, these being the conditions recommended by Sherman, 

 Kendall, and Clarke (10) for all determinations of diastatic activity. 

 At the expiration of this period action was stopped by adding sufficient 

 Njio sulphuric acid to make the total volume a N/200 solution, and an 

 aliquot equal to that taken before the digestion was drawn off for the 

 determination of its reducing sugar content. The soluble proteins were 

 precipitated and the reducing sugars determined by the method out- 



