ANNUAL REPORT, 1940 i7 



Precursors of Ligiiin. Data obtained from an investigation on Kentucky 

 blue grass {Poa pratcnsis) and red clover ( Trifolium prafcnse) showed no 

 apparent relationship between pectic substances, hemicelluloses, and lignin. 

 The lignin in red clover was associated with approximately an equal 

 amount of pectic substances. On the other hand, Kentucky blue grass, 

 containing an amount of lignin nearly equal to that of red clover, showed 

 little more than a trace of pectic substances. The older plants contained 

 about the same percentage of the pectic substances as the younger ones. 

 The percentage of total hemicelluloses in Kentucky blue grass was about 

 twice that in red clover. 



It seems, therefore, that variations in the proportions of tlie three sub- 

 stances in the two species are probably due to differences in cell struc- 

 ture rather than to transformations; and that pectic substances are not 

 found chief!}' in the younger tissues. 



A description of this work can be found in Science 91:95-96, 1940; and in 

 Plant Physiol. 15:327-334, 1940. 



Effect of Storage and Processing on Carbohydrates of Some Varieties 

 of Edible Onions. (Emmett Bennett.) A description of this project was 

 given in the annual reports for 1938 and 1939. The results from investiga- 

 tions on the storage of the Ebenezer onion indicated the following: 



1. Soluble carbohydrates constituted approximately 60 percent of the 

 dry matter of the onion. 



2. Reducing sugars accumulated to the greatest extent in the coldest 

 storage. 



3. Loss of total soluble carbohydrates was negligible in the onions 

 which remained sound in storage. 



4. The chief losses in storage were due to decay and sprouting. 



5. Low temperatures retarded the losses. 



Boiling onions in the usual way for consumption decreased the content 

 of non-reducing sugars about 13 percent. 



Details of this work have been summarized and submitted for publication 

 in the Proceedings of the American Society for Horticultural Science. 



Chemical Changes in the Cooking of Vegetables. (M. E. Freeman and 

 W. S. Ritchie.) The cells of baked potatoes are separated to a greater 

 extent in mealy tissue than in waxy tissue. Previously it was shown that 

 this does not seem to be caused by the lack or weakness of the pectinous 

 cementing material between the cells. New technique has given additional 

 evidence of the cell separation in mealy tissue. When slices of freshly 

 baked potatoes are dried, the mealy tissue becomes very porous. In the 

 waxy tissue, however, the cells adhere so firmly that the material shrinks 

 to a dense vitreous mass. The difference between mealy and waxy tissue 

 is so apparent that the texture can be easily scored. There are several 

 important advantages in this method of scoring texture: (1) the dried 

 slices can be kept as a permanent record of any test; (2) the permanent 

 standards can be selected and used for direct comparison with any test; 

 (3) standards can be easily exchanged by any laboratories that wish to 

 compare their results on the same scoring basis. 



From the foregoing observations, it would seem that a quantitative 

 measure of the pore surface or pore volume of the dried slices might serve 

 as a quantitative measure of texture. Preliminary experiments on this 

 point have met with some success. 



