186 THE VITAMINS 



concentrates except that the juice was held for 24 hours preserved with 

 six ounces of potassium metabisulfite to 100 gallons was also used. 

 The concentrated whole juice retained practically all of the antiscorbutic 

 value of the original juice. The clarified sirup showed slight but not 

 significant destruction of vitamin C. The desiccated juice, although two 

 years old at the time of testing, was found to have retained a good 

 proportion of its antiscorbutic properties and the dried whole orange 

 proved to be a highly concentrated source of vitamin C. The concen- 

 trated lemon juice was not relished by the guinea pigs but was appar- 

 ently a rich source of vitamin C. 



The value of commercial orange sirup as an antiscorbutic was also 

 demonstrated by Priston (1926) in studies conducted in England in 

 behalf of the British Admiralty. The sirup, when first tested after 

 storage from ten to sixteen weeks at warehouse temperature and from 

 five to twenty-four weeks in the icebox at 8° C, was protective in three 

 out of four cases in a dosage of 0.3 cubic centimeter of undiluted sirup, 

 or about one-third of the amount required of fresh orange juice. Pro- 

 longed storage at icebox temperature did not reduce the potency to any 

 marked extent, but storage at 19° C. for 42 weeks reduced it to about 

 one-third, and for 24 weeks at temperatures varying from 8° to 37° C. 

 to one-tenth the original value. Priston estimated that 50 gallons of 

 the concentrate would probably contain sufficient vitamin C to supple- 

 ment the supply available in the tropical war diet of 1,200 men for three 

 months and that economy could be effected by substituting this con- 

 centrate for the lime juice then being issued. 



Willimott and Wokes (1927c) are of the opinion that there is 

 some connection between the biochemical activities taking place in the 

 flavedo (outer peel) of citrus fruits and the constituents of both peel 

 and juice. A comparative study of the flavedos of oranges (California 

 Navel), lemons (fresh Palermos) and grape fruit (Florida) showed 

 the presence of vitamin C in the flavedo of the orange but not of the 

 lemon or grapefruit. In their experiments one gram of fresh orange 

 peel, or 1.5 cubic centimeters of fresh orange or lemon juice appeared 

 to be adequate protective doses for guinea pigs. Grapefruit was not 

 quite as rich in vitamin C as lemons or oranges. In view of the known 

 sensitivity of both vitamin A and vitamin C toward oxidizing agents 

 the flavedo and juice of the three fruits were tested for oxygenase and 

 peroxidase. Oxygenase was always absent but peroxidase was present 

 in both flavedo and juice. In the flavedo the concentration was higher 

 in grapefruit than in the oranges — thus affording a possible explana- 

 tion of the relative amounts of vitamin C in the two fruits. It would 



