May IS, 1920 Effect of Premature Freezing on Composition of Wheat 183 



which habitually come under the observation of the State Grain Labora- 

 tory. The kernels were not shrunken, nor was there more than a small 

 percentage of green kernels. The large majority of kernels from the 191 7 

 series, however, had the well-known blistered appearance extending over 

 the entire surface of the kernel, which is usually conclusive evidence 

 that the grain has been badly frozen before reaching maturity. The 

 wheat from the corresponding plot of the 1918 series was much less 

 blistered than that from the 191 7 series. All the other samples presented 

 the appearance of mature wheat and had been cut before the first killing 

 frost. The samples just discussed may be readily identified in the 

 tables which follow. 



Special attention is invited to the manner in which the grain from each 

 series was handled after cutting, since there is strong evidence from the 

 chemical analyses that the two different methods of handling and storage 

 exerted a very appreciable effect on the biological activities wdthin the 

 kernel, aside from the effects of freezing. The wheat from the 191 7 

 series was brought to the granary shortly after cutting and thrashed when 

 dry enough to permit. Samples for subsequent analyses were then stored 

 in a room nea,r the college heating plant where the temperature was ab- 

 normally high and where the grain soon became drier than grain stored 

 under normal conditions. It remained there for more than a year 

 before being analyzed. The grain from the 191 8 series, however, was 

 allowed to remain in the field, after it was cut and shocked, until late 

 in the following January, when it was taken to the granary and later 

 thrashed. This grain was therefore subjected to several months of 

 severe weathering in the field, and after being thrashed a considerable 

 portion of it presented the bleached appearance which is characteristic 

 of grain which has stood in the shock and undergone weathering. In 

 the discussion of the analytical results which follow, attention will be 

 called to chemical differences which have apparently been caused by the 

 different methods of handling the grain from the two series of experi- 

 mental plots. 



EFFECT 'of freezing ON NITROGEN COMPOUNDS 



In studying the chemical composition of the wheat frozen at different 

 stages of growth, particular attention was directed to the effect of freezing 

 on the nitrogen compounds, since it is the gluten-forming proteins of 

 wheat that give flour its bread-making power. The influence of the 

 other constituents of normal wheat flour on its baking strength are for 

 the most part considered to be indirect and are of importance only in so 

 far as they affect the gluten. In order to estimate the extent to which 

 premature freezing arrests the building up of the proteins from the less 

 complex nitrogen compounds, determinations of the amounts of total 

 nitrogen, nonprotein nitrogen, a-amino nitrogen, amid nitrogen, and 



