ASCORBIC ACID IN TOMATOES 9 



tomatoes grown in his own garden and found the canned equivalent to the raw 

 in ascorbic acid content. Kohman, Eddy, and Zall (1930) found that canned 

 tomatoes protected guinea pigs from scurvy as well as did the fresh fruit. Clow 

 and Marlatt (1930), using the 16-day recovery method, reported that cold-packed 

 canned tomatoes contained the same amount of ascorbic acid as the raw tomato. 

 Delf (1925), an English investigator, found that the canning of tomatoes de- 

 stroyed about 75 percent of the ascorbic acid; but Kohman (1929) stated that the 

 English canning method is not the commercial method employed in America 

 and, consequently, differences in results are to be expected. Vercellana (1924) 

 reported that preserved tomatoes contained no ascorbic acid. Caro and Perling 

 (1936) found that the ascorbic acid of canned tomatoes varied greatly from that 

 of the fresh product. All of these experiments were conducted by biological 

 methods which are not sensitive to the small differences detected by the chemical 

 lest, but the larger differences mentioned cannot be accounted for by the limita- 

 tions of the method used. 



Rogers and Mathews (1938) found, by chemical tests, that commercial and 

 home-canned tomatoes each contained 0.14 mg. of ascorbic acid per cc. Daniel 

 and Rutherford (1936) compared the canning of tomatoes in tin cans and glass 

 jars. The loss due to the canning was 12 percent in the tin cans and 21 percent 

 in the glass jars. They also found that storage of canned tomatoes over a period 

 of 6 months destroyed from 10 to 23 percent of the ascorbic acid. Clow and 

 Marlatt (1930) and Hess and Unger (1919) found only a slight loss after one 

 year's storage. Delf (1925) reported 5 percent loss in four years' storage at lab- 

 oratory temperature. Hanning (1936), investigating canned strained tomatoes, 

 found marked variation in ascorbic acid content of the crops of four successive 

 years. 



Canned Tomato Juice 



La Mer, Campbell, and Sherman (1921) studied the effect of heating upon the 

 destruction of ascorbic acid in tomato juice. They measured the percentage loss 

 in open containers for periods of one to four hours at 60°, 80°, and 100° C. The 

 velocity of destruction in the experiments decreased with the time and in a 

 greater degree than would be expected if the reaction followed the monomolecular 

 reaction law. The percentage of ascorbic acid destroyed was found to vary 

 empirically as the fourth root of the time. The reaction was not appreciably 

 sensitive to ordinary light. The velocity of most chemical reactions is at least 

 doubled for each increase in temperature of 10° C. Delf (1925) first pointed out 

 that ascorbic acid does not follow this law. La Mer (1921) found that between 

 60° and 80° C, a rise in temperature of 10 degrees caused only 1.2 times more 

 destruction of ascorbic acid for a given period. Between 80° and 100 ° C, a rise 

 in temperature of 10 degrees increased the destruction only 1.1 times. Con- 

 vincing data that oxidation is the major factor causing destruction and that 

 ascorbic acid is relatively stable toward heat has been presented by Kohman, 

 Eddy, and Carlsson (1924). They showed that when the oxygen was removed 

 from apples by the respiratory process these apples could be canned without any 

 loss of ascorbic acid. This evidence may well be considered by manufacturers 

 of tomato juice. Tomatoes for juice are heated at a high temperature over a 

 period of time to soften the flesh and then are forced or cycloned through a fine 

 screen. At this stage of the process air may be entrapped in the juice, causing 

 subsequent oxidation and destruction of ascorbic acid. 



Hicks (1931) found that vacuumization during cycloning resulted in maximum 

 ascorbic acid retention. Pilcher (1932) stated that air-cycloned, cold tomato 



