Ascorbic Acid (Vitamin C) in Tomatoes and Tomato Products 



By Walter A. Maclinn, Instructor in Horticultural Manufactures, and Carl R. 

 Fellers, Research Professor of Horticultural Manufactures 



INTRODUCTION 



The tomato ranks among the richest and most widely used of antiscorbutic 

 foods, but in spite of its popularity, comprehensive studies of the factors influenc- 

 ing the ascorbic acid content in the tomato are lacking. True, considerable at- 

 tention has been directed to the evaluation of the various manufactured tomato 

 products, in terms of ascorbic acid; but the effect of season, variety, maturity, 

 storage, and many other factors have been only incompletely studied. 



Previous to 1932 when Tillmans, Hirsch, and Hirsch discovered a chemical 

 titration method of determining ascorbic acid, the only method available was the 

 90-day, guinea-pig bioassay. Naturally, progress was slow under these condi- 

 tions, and in many cases, conflicting results were reported. Furthermore, the 

 animal method is not sufficiently accurate to determine small differences in ascor- 

 bic acid content. Another recent discovery (Tillmans, Hirsch, and Dick, 1932) 

 was that the ascorbic acid in fresh fruits and vegetables often is present in the 

 reversibly oxidized form of dehydroascorbic acid. There is still some question 

 as to whether this substance possesses the full value of ascorbic acid in the pre- 

 vention and cure of scurvy. 



The first step in this investigation naturally seemed to be a comparison of the 

 newly devised chemical titration method with the standard animal bioassay. 

 This had not been done previously for tomato products. Since sampling methods, 

 reagents, and technic were not well standardized, it was necessary to make a 

 careful quantitative study of these several factors before the rapid chemical 

 methods could be adapted with a degree of assurance to the evaluation of ascorbic 

 acid in tomatoes and tomato products. 



REVIEW OF LITERATURE 



There is difficulty in covering the entire literature on tomato and tomato 

 products as a source of ascorbic acid, because in some cases the tomato analysis 

 may be secondary in importance to some other phase of ascorbic acid investiga- 

 tion, and therefore no mention is made of the tomato in the title or summary. 

 There are a number of reviews or summaries of ascorbic acid investigations that 

 refer to the tomato: Kohman in 1929, Sherman and Smith in 1931, Report of the 

 British Medical Research Council in 1932. Fellers in 1936, Daniel and Munsell 

 in 1937, and less complete surveys by Bacharach (1933), Smith (1929), Scheunert 

 (1930), Priestly (1933), Dutcher (1932), Fellers (1935), and Cowell (1936). 



Besides the discussion of salient papers on the ascorbic acid content of tomatoes 

 and tomato products, this review includes a summar\- in tabular form of all 

 reported references however brief (Table 1). 



The terminology used in the reports varied widely, including Sherman units, 

 milligrams of ascorbic acid, and even qualitative words such as good, fair, or poor. 

 For uniformity in this summary table the ascorbic acid content is expressed in 

 milligrams per gram and international units. An international unit represents 

 the antiscorbutic activity of 0.05 mg. 1-ascorbic acid. Factors for converting 

 some of the reported results into international units could not be accurately 



