FACTORS INFLUENCING DIASTASE FORMATION 227 



normal iodine solution, which had been standardized by titrat- 

 ing it against a solution of sodium thio-sulphate. The tube 

 which gave no reaction for starch or any of the dextrines when 

 the iodine was added, was selected as the one determining the 

 end point of the conversion. The moisture content of the air- 

 dry barley was ascertained and the diastase activity determined 

 in a like manner. 



Temperature control 



In the course of experimentation, two different temperature 

 controlling devices, a water bath with thermostatic control and a 

 temperature case, were used. The former was used for experi- 

 ments at 30°C. For lower temperatures than 30°C. this was 

 impracticable and the cases with chilling devices were employed. 



In order to keep the starch solution at an even temperature 

 during its conversion by the diastase extract, another bath was 

 set up and maintained at a temperature of 50°C. 



3. EXPERIMENTAL RESULTS AND DISCUSSION 



The air-dry barley grain under the storage conditions of the 

 laboratory contained 8.76% of water. At temperatures of 5, 

 10, 15, 20, and 25°C, the diastase of this grain as determined 

 by the period required to hydrolyze a starch solution of given 

 concentration, is 44 hours, 00 minutes; 44 hours, 00 minutes; 42 

 hours, 45 minutes; 42 hours, 15 minutes; and 41 hours, 15 min- 

 utes respectively. These results — table 1 — express the temper- 

 ature effect on diastase in barley with 8.76% of water. The 

 quantity of diastase in the barley grain at the above tempera- 

 tures varied only slightly during a period of from 2 to 3 weeks. 

 At a temperature of 30°C. the initial diastase is slightly increased 

 and this continued for the period of exposure — 12 hours. The 

 results are shown in table 2. 



The results given in table 3 show quite clearly that the vapor 

 tension method is well adapted for furnishing different amounts 

 of water to samples of air-dry grain. At 5°C. the water content 

 of barley grains suspended above solutions of different concen- 



