46 MASS. EXPERIMENT STATION BULLETIN 417 



oxidants for lard; but these compounds, while possessing antioxidant powers, 

 imparted an objectionable off-flavor to corn and cottonseed oils. In using anti- 

 oxidants with edible oils it is important that the product be fresh and in good 

 condition to start with; otherwise, much of the effectiveness of added antioxi- 

 dants it is lost. 



Amber glass bottles were found to be satisfactory as containers for liquid edible 

 oils when stored under normal commercial conditions, and also convenient from 

 the standpoint of use by the consumer. 



Preliminary results indicate that riboflavin is quite stable during the canning 

 and processing of vegetables. In such products as cut asparagus and cut green 

 beans, there is a marked tendency for the riboflavin to leach out of the product 

 into the brine. Thus if the brine were discarded when the can was opened, much 

 of the riboflavin would be lost. 



The carotene content of such vegetables as asparagus, green beans, corn, and 

 peas was found to be very stable during canning and subsequent storage of the 

 canned products in both glass and metal containers. Storage in bright sunlight 

 for prolonged periods of time appeared to have no significant effect on the caro- 

 tene content of glass-packed vegetables. 



Thirteen different types of commercial and home-canning glass and metal 

 containers were compared for their effect on the stability of the ascorbic acid in 

 canned tomato juice. The loss of ascorbic acid during eight months' storage 

 varied from approximately 35 to 50 percent, depending upon the type of con- 

 tainer. In general, vacuum-sealed, commercial-type glass containers, plain tin 

 cans, and home-canning jars sealed with two-piece metal lids were found to be 

 superior from the standpoint of ascorbic acid retention in canned tomato juice. 

 The differences observed in the different kinds of containers appear to be due 

 largely to the amount of oxj'gen in the headspace and dissolved in the juice during 

 processing and storage. 



D-iso ascorbic acid proved satisfactory as an antioxidant for preventing the 

 discoloration of freshly peeled peaches and pears, home-canned peaches and 

 pears, and tomato catsup. In working with pure solutions, d-iso ascorbic acid 

 was oxidized more rapidly than 1-ascorbic acid (vitamin C). D-iso ascorbic 

 acid was preferentially oxidized when used as an antioxidant for 1-ascorbic acid 

 and may be considered a good antioxidant for the latter substance. When these 

 theoretical findings were applied to glass-packed tomato juice, none of the original 

 1-ascorbic acid was lost, even under severe storage conditions, when small amounts 

 of d-iso ascorbic acid had been added to the bottled juice. In addition to pre- 

 venting a loss of 1-ascorbic acid, the added d-iso ascorbic acid also prevented the 

 juice from darkening when stored at high temperatures, and the juice main- 

 tained its original fresh flavor. For practical purposes, it would appear that, 

 for optimum effectiveness, d-iso ascorbic acid should be added to tomato juice 

 in amounts equivalent to 25 to 30 milligrams per pint. 



Oxidation-reduction potential studies have tended to confirm the finding 

 that d-iso ascorbic acid is an antioxidant for 1-ascorbic acid, itself an antioxidant. 

 The superior antioxidant properties of d-iso ascorbic acid over 1-ascorbic acid 

 seem to be correlated with the greater poising action of d-iso ascorbic acid, rather 

 than with their respective redox potentials. Citrate-buffer ascorbic-acid packs 

 were put up in plain tin cans and in commercial all-glass jars and stored at 70°F. 

 and at 100°-110°F. The eventual ascorbic acid loss was the same in both types 

 of containers stored at 100°-110°F., although the rate of loss was initially greater 

 in the glass container. The potential of the tin-packed solution was lower than 

 that of the glass-packed. In general the packs stored at 70°F. evidenced the 

 same changes, except that slightly less ascorbic acid was lost in the tin container 



