188 THE VITAMINS 



Largely no doubt on account of the natural high acidity and the 

 low oxidation potential of their juice tomatoes may be canned without 

 apparent loss of antiscorbutic value, and may even retain a relatively 

 high antiscorbutic value after drying. 



Givens and McClugage (1919) found that when 1 gram of dried 

 tomato which had not been heated above 40° C. was fed per guinea 

 pig per day no scurvy developed. Since this may have been considerably 

 more than the minimum necessary for complete protection, these ex- 

 periments show clearly that tomatoes may retain a considerable amount 

 of antiscorbutic vitamin after drying; but do not indicate what propor- 

 tion of the vitamin originally present may have been destroyed by the 

 drying process. 



In the experience of Hess and Unger (1918), 4 cubic centimeters 

 and in that of Sherman, La Mer and Campbell (1921), 3 cubic centi- 

 meters daily of canned tomato juice was found to afford the guinea pig 

 complete protection from scurvy. In tomato juice of natural acidity, 

 the antiscorbutic vitamin was found to be fairly stable to heat, boiling 

 for one hour destroying only about one-half ; and for four hours only 

 about two-thirds of the vitamin originally present. When the acidity 

 was partially neutralized, and still more when the tomato juice was 

 rendered alkaline, the destruction of the vitamin by heat became more 

 rapid. (Sherman, La Mer, and Campbell, 1921, 1922.) Kohman 

 (1928) has reported some loss in vitamin C in the preparation of com- 

 mercial tomato concentrate (puree), but not in proportion to the con- 

 centration. Weight for weight the tomato pulp or puree is thus richer 

 in vitamin C than raw tomatoes. The rate of destruction of the anti- 

 scorbutic vitamin of tomatoes at different temperatures and concentra- 

 tions of hydrogen ion will be referred to again in connection with the 

 summary of chemical and physical properties of vitamin C toward the 

 end of this chapter. 



The increasing use of ethylene gas in the ripening of fruits and 

 vegetables has led to investigations in several laboratories of the relative 

 content of vitamin C in tomatoes ripened in various ways. Studies by 

 Clow and Marlatt (1930) led to the conclusion that ripe tomatoes are 

 much richer in vitamin C than green tomatoes even when the tomatoes 

 are ripened in the dark after removal from the vines and that ethylene- 

 ripened tomatoes are richer in vitamin C than green tomatoes, but not 

 quite so rich as tomatoes thoroughly ripened by standing at room tem- 

 perature until the tissues are considerably softened. In these reports 

 the impression is given that the method of ripening is not so important 

 a factor as the extent of ripening for it is noted that ripe greenhouse 



