262 ASCORBIC ACID 



which is known to be an important factor in determining the concentration 

 of ascorbic acid in fruits and seeds. Thus, for instance, garden peas in the 

 early stages of development have been found to contain as much as 160 

 mg. of ascorbic acid per 100 g., although when they are ready for harvesting 

 the value falls to approximately 25 mg. per 100 g. Immature walnuts' have 

 been found to contain between 1500 and 2500 mg. of ascorl)ic acid per 100 

 g., although there is a steady decline as lignification takes place until the 

 hardened nut has a negligible antiscorbutic value. With some vegetables, 

 however, notably storage organs, such as potatoes, and leaves, such as spin- 

 ach, the concentration of ascorbic acid has been found to remain relatively 

 constant during the whole of the growth period. 



In some fruits and vegetables, variety is important in determining the 

 concentration of ascorbic acid in the tissues, but in others varietal effect 

 is negligible compared with other factors. Manurial conditions may possibly 

 also affect the amount of ascorbic acid, and some soil nutrients, such as 

 molybdenum, have been found to increase the concentration of the vitamin 

 in plants. Climatic conditions may also have an effect, and in localities 

 where the incidence of sunshine is high there appears to be a corresponding 

 increase in average ascorbic acid content. Seasonal variations may, however, 

 occur which are not obviously related to climatic conditions. For instance, 

 a laboratory in England made a survey of the ascorbic acid value of freshly 

 picked black currants between 1936 and 1946. The results of testing many 

 hundreds of samples of many varieties of this fruit from different localities 

 showed relatively consistent results for the yearly average with the excep- 

 tion of 1941. In this year, the average concentration fell to 138 mg. per 100 

 g. as against 200 to 230 mg. per 100 g. for the other periods under review. 



Nevertheless, in spite of the wide limits within which the ascorbic acid 

 content of any fruit or vegetable might be expected to vary, the average 

 figures quoted by vaaious investigators do in fact show reasonably good 

 agreement. For this reason, the compiling of a table showing such data has 

 seemed justifiable (Table V), but the possibility of significant variation 

 from these figures for individual batches must be appreciated. The litera- 

 ture has been searched to make this table as comprehensive as possible, 

 but reference may be made to some sources which have been found of 

 special value. ^"^* Only those plant organs which are normally used for food 



» L. J. Harris and M. Olliver, Biochem. J". 36, 155 (1942). 



2 M. Olliver, Chemistry and Industry 62, 146 (1943). 



' B. S. Piatt, Tables of Representative Values of Foods Commonly Used in Tropical 



Countries, Med. Research Council {Brit.), Spec. Rept. Ser. 253 (1945). 

 * Nutritive Values of Wartime Foods, Med. Research Council (Brit.) War Mem. 14 



(1945). 

 6 H. E. Munsell, L. O. Williams, L. P. Guild, C. B. Troescher, G. Nightingale, and 



R. S. Harris, Food Research 14, 144 (1949). 



