The antiscorbutic factor is the most sensitive of the three vitamins to heat and drying. The failure of dried vegetables and herbs and preserved meats and fish to prevent or cure outbreaks of scurvy has been demonstrated repeatedly in the naval history of every country.59 Stefanson 60 has asserted on the basis of his Arctic experience that the antiscorbutic properties of fresh foods are diminished or entirely lost in the course of any of the ordinary methods of preservation, canning, pickling, drying, etc. Chick and Hume61 assert that all dried foodstuffs, including desiccated vegetables examined by them, are more or less deficient in antiscorbutic vitamin. At first they thought the temperature at which the tissues were dried seemingly was a matter of indifference, but later work indicates this statement to be too sweeping.

52Emmett and Lurot, J. Biol. Chem. 43, 205, 1920.

53 Seidell, Bull. Hyg. Lab. U. 8. P. H. 1916, 31, 364.

54 Chick and Hume, J. Roy. Med. Corps, 29, 121, 1917.

55 Daniels and McClurg, J. Biol. Chem. 37, 201, 1919.

56 McCollum, Simmonds and Pitz, J. Biol. Chem. 29, 521, 1916.

57 Funk, Proc. Soc. Exp. Biol. Med. 14, 9, 1916.

58 Suguira and Benedict, J. Biol. Chem. 39, 421, 1919.

The partial or complete loss of C during heating has been recorded by many observers working with many different foodstuffs. Cabbage, which is rich in C in the raw state, has been a favorite subject for experimentation. Campbell and Chick62 found that heating in water for about one hour at 90° to 100° C. caused a loss of about 70 per cent of the antiscorbutic power of cabbage, and state that further loss may be expected to take place if the canned material is stored for any length of time before feeding. Delf63 estimates that about 70 per cent of the original value of cabbage is lost after one hour's heating to 60° C, and over 90 per cent after the same period at 90° C. Twenty minutes heating at 90° to 100° C appears to have practically the same effect as heating for an hour at 60° C. In these experiments a small amount of cabbage was added to a diet of grain and autoclaved milk which had been found to produce scurvy when fed alone. When the autoclaved milk was omitted and the cabbage ration was increased to from 15 to 30 g. the destructive effect of heat was less noticeable, even when the cabbage was heated to 100° to 130° C for one to two hours.

Delf suggests that this may be due to the fact that in the later experiments with the larger ration both A and C were drawn from the same source. Much evidence has been accumulated by the group of workers at the Lister Institute of Preventive Medicine, London, pointing to a distinct and separate action of these two factors in the nutrition of young guinea pigs. Tozer has, how-. ever, found that a lack of growth fat-soluble factor in the diet is accompanied by a series of changes in the histology of the rib-junction which is almost indistinguishable from that caused by a slight deficiency of antiscorbutic factor. It is therefore not impossible that the antiscorbutic value of a diet may be enhanced and may show greater heat stability when the antiscorbutic factor and the growth fat-soluble factor are derived from the same foodstuffs.

59 See Ch. XII.

60 Stefanson, Jour. Am. Med. An. 71, 1715, 1918.

61 Chick and Hume, Tr. Soc. Trop. Med. Hyg. 10, 141, 1917.

62 Campbell and Chick, Lancet, 1919, ii, 320.

63 Delf, Bioch. J. 12, 416, 1918.

Hoist and Frdlich64 found that freshly expressed cabbage juice lost its antiscorbutic power after heating from 60° to 100° C. for ten minutes. The destruction was not so complete if the juice was acidified with 0.5 per cent of citric acid before heating. Delf 65 failed to confirm this result with acidified cabbage juice, and Hoist and Frd-lich themselves found that the presence of acid did not prevent the destruction of the C in dandelion or sorrel juice.

According to Givcns and Cohen 66 cabbage which has been heated in an oven for two hours at 75° to 80° C, then dried at 66° to 70° C. for several days loses its antiscorbutic power completely. Cabbage which has been cooked for 30 minutes, then subjected to drying for two days at 65° to 70° is likewise devoid of antiscorbutic power.

Ellis, Steenbock and Hart67 report that desiccation at 65° C. even in an atmosphere of carbon dioxide causes destruction of the antiscorbutic in cabbage, which indicates that the destructive agency in this case is heat rather than an oxidation. On the other hand, the same experimenters find that oxidizing agents will destroy the C in orange juice, although it is not affected by aeration.674

With regard to other vegetables there are fewer observations, but the general trend is the same. Campbell and Chick68 found that string beans which had been heated to 90° to 100° C. for an hour on two successive days had lost about 90 per cent of their content of C. Chick and Delf 69 note that a considerable amount of the antiscorbutic power generated in dried peas and lentils on germinating is destroyed by boiling, and that the cooking of these should therefore be as short as possible. McClendon, Cole, Engstrand, and Middle-kauf70 assert that heating at 70° C. gelatinizes the starch without destroying the C in sprouted cereals. They base this statement on the fact that a guinea pig lived for 34 days without showing scorbutic symptoms on an exclusive diet of sprouted cereals which had been heated to this temperature.

64 Hoist and Frdlich, Ztechr. Hyg. 72, 1, 1912.

65 Delf, Bioch. J. 12, 416; 14, 211.

66Givens and Cohen, J. Biol. Chem. 36,127,1918.

67 Ellis, Steenbock and Hart, J. Biol. Chem. 46, 967, 1921.

67a See also the work of Sherman, LaMer and Campbell referred to on p. 102.

68 Loc. tit. 69Chick and Delf, Bioch. J. 13, 199.

70 McClendon, Cole, Bngstrand and Middlekauf, J. Biol. Chem. 40, 243, 1920.