ANNUAL REPORT, 1939 29 



The Iron, Copper, Zinc, and Iodine Content of Fruits and Vegetables Used 

 as Human Food. (E. B. Holland, W. S. Ritchie, and C. P. Jones.) As in previous 

 years various samples (21) of human and cattle foods have been collected and 

 their analysis is well under way. They include cereals, processed human foods, 

 proprietary foods, vegetables, dried citrus pulp, and young succulent grasses 

 and clovers. 



Dark Centers in Rutabagas. An experiment was conducted with two varieties 

 of rutabagas, American Purple Top and White Cape, in four counties of the 

 State during 1938 to note the effect of borax in preventing dark centers. The 

 extremely wet season may have vitiated the results to some extent, but samples 

 from treated plots showed nearly twice as much boron as from the untreated. 

 Hollow heart, however, was more noticeable than dark centers, which had been 

 characteristic in previous years. No samples showing the disorder were available 

 this season. 



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

 Ritchie.) Since mealy potatoes are more desirable in most American retail 

 markets, attempts have been made to ascertain the chemical or physical proper- 

 ties of cooked potato flesh that are causally related to this character. Previous 

 workers have observed that in mealy potatoes the cells separate to a greater 

 extent and the moisture content is usually lower. 



The fact that the cells of mealy potato tissue separate readily suggested that 

 the pectic materials binding the cells together would be more easily disintegrated 

 and dissolved in mealy potatoes than in waxy potatoes. The careful fractionation 

 and isolation of the pectins in 20 samples (8 varieties) varying widely in texture 

 did not, however, indicate a significant difference between mealy and waxy 

 potatoes. While cooking brought about rapid changes in the pectic material, 

 the extent of these changes as measured by the extraction of pectin did not dis- 

 tinguish the mealy from waxy potatoes. 



Additional information concerning some characteristic properties of potato 

 pectin was obtained. In the preparation of samples for pectin analyses, a mild 

 heat treatment designed to inactivate the destructive enzymes was found to alter 

 the pectin fractions. Rapid drying of sliced potatoes in a current of warm air 

 was superior. In potatoes the three pectin fractions generally described for plant 

 material were not clearly defined. The data led to the suggestion that potato 

 pectin can be adequately defined by two fractions: (1) a fraction soluble in 

 ammonium salts but insoluble in hot water; (2) a fraction easily dispersed by 

 hot water but not by cold water. Further details of this investigation have been 

 submitted for publication in Food Research' under the title "Pectins and the 

 Texture of Cooked Potatoes." 



A number of investigators have attempted to correlate mealiness with low 

 moisture content, high dry matter content, and /or high starch content. While 

 the majority admit that there is probably a fairly high correlation, there are 

 other conclusions to the contrary. About 200 tubers (7 varieties) were individually 

 tested for mealiness and analyzed for moisture. The moisture contents ranged 

 continuously from 87.4 to 69.1 percent; consequently the three classes of high, 

 intermediate, and low moisture had to be arbitrarily defined. Three degrees of 

 mealiness, high, medium, and low, were independently estimated. When the 

 data were tabulated under these two classifications, it became apparent that there 

 was a high degree of correlation between low moisture content and mealiness 

 in these potatoes. 



However, waxy potatoes cannot be made mealy simpl}' by expelling more 

 water by prolonged cooking. There appear to be unknown factors influencing 

 the relative ability of tubers to retain moisture during the cooking process. 



