May IS. 1920 Effect of Premature Freezing on Composition of Wheat 187 



Table III. — Some effects of freezing on carbohydrates of Marquis wheat 



The data in Table III show that the percentage of reducing sugars 

 increases with the severity of the freezing, as would be anticipated. 

 The figures for reducing sugars in the most severely frozen samples of 

 both series offer further evidence that either the freezing in the 19 17 

 series was far more severe than in the 1918 series or the different methods 

 of handling the two series after cutting resulted in different biochemical 

 activities within the kernel. Also, as would be expected, there is more 

 soluble starch and dextrin in the frozen samples than in the matured 

 ones. There seems to be no apparent relationship between the sucrose 

 content and the severity of freezing. 



EFFECT OF FREEZING ON ACIDITY 



The general effect of freezing on the acidity of the samples of wheat 

 and flour used in these experiments was briefly studied by titrating 

 water extracts with NI0.05 alkali, using phenolphthalein, although 

 electrometric titrations with the hydrogen electrode might be preferable. 

 With reference to acidimetric titrations of cereal extracts, Birckner (z) 

 has recently shown that the addition of alcohol to water extracts con- 

 taining amino compounds increases the acidity of the extracts in pro- 

 portion to the amount of amino compounds present. Water extracts 

 of the wheat and flour samples in question were therefore titrated with 

 and without alcohol. According to Birckner the difference between 

 the two titrations should be an index to the amino compounds present, 

 and a comparison of these differences with results obtained by the use 

 of Van Slyke's microapparatus (see Tables I and II) should be of interest. 

 In the alcoholic titrations the water extracts were diluted with equal 

 volumes of neutral alcohol. The results are set forth in Table IV. 



In examining the values expressed by the differences between the 

 titrations with and without alcohol for the respective samples, it may 

 readily be seen that not only do these values increase as the severity of 

 freezing increases but the extent of the increase in almost all instances 

 keeps pace with the figures for nonprotein and a-amino nitrogen as 

 actually determined and shown in Tables I and II. This is in close 

 agreement with the findings of Birckner (/). 



