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analyses on the same individual sample, so that the evidence offered points to the chemical identity of the gliadins from the different varieties of wheat and to the conclusion that the differences in behavior, if in fact they are attributable to the proteins present, are to be ascribed to differences in physical state rather than chemical constitution. The close agreement of the results of those determinations, such as cystine, tyrosine, and tryptophan, in which the probable error is small, lends particular support to this conclusion. The same comment may be made with respect to the glutenin samples with the possible exception of the ammonia fraction which seems
Vol. 16, No. 1
to be somewhat lower in the Forty-Fold sample than was the case with the other samples examined. A new preparation of lime was used on this sample, which may have had something to do with the lower result noted here. ACKNOWLEDGMENT The authors wish to extend their thanks to the Sperry Flour Company for its cooperation in providing the fellowship under which this work was done, and to Bert D. Ingels of this company for selecting the wheats and preparing the flours for this investigation.
Vitamin C in Canned Foods' By Walter H. Eddy and Edward F. Kohman COLUMBIA UNIVERSITY,NEWYORK,N. Y.,AND NATIONALCANNERS' ASSOCIATION,WASHINGTON, D. C.
HE experiments reported herein are the first of a series of joint researches undertaken to establish to what extent vitamin C is destroyed in present canning methods, the causes underlying this destruction, and to evolve better methods for its prevention. Recently, evidence was presented by Eddy and associates2tending $0 show that when cabbage is cooked to palatable form, either by boiling in an open kettle or by cooking in a pressure cooker, 20 grams per day is the amount necessary to protect a guinea pig from scurvy, whereas 1 gram of raw cabbage per day suffices for this purpose. From control experiments reported a t that time it followed that home cooking methods result in practically 95 per cent destruction of vitamin C in both cabbage and the rutabaga turnip. It has been the practice t o infer from such experiments that if canned material is subjected to similar temperatures for similar periods of time the vitamin destruction in canned foods will be of the same order. Such inferences ignore the possible influence of other factors concerned in vitamin C destruction, among which are the presence or absence of oxygen, variation in reaction (pH), and possibly the presence or absence of oxygen activators. Kohman3 has already called attention to the desirability of investigating the oxygen content of canned foods as bearing on this point. Still more recently, Zilva4 has produced evidence tending to show that the destruction of vitamin C is an oxidation process which proceeds rapidly in alkaline solutions even a t room temperature, and also, but more slowly, in acid medium.
T
EXPERIMEXTAL I n beginning this series it seemed particularly desirable first to determine the actual destruction of vitamin C in a foodstuff subjected to commercial canning in which the only variables should be the degree of temperature used in the processing and the duration of the heating process. For this purpose cabbage was used. This was harvested about November 15, 1923, and canned a few days after as follows: Cabbage heads were cut in quarters, all the bad outer leaves stripped off, and the hearts cut out. Then a solid piece was cut out of the quarter to fit approximately into a No. 2 can. If this did not make 11 ounces, sufficient loose material was filled in to make that weight. After the cabbage was packed in cans, these were filled with hot water drawn from the factory tubs and through which live steam was passed to boil it actively for 2 or Received September 26, 1923. J. Home Econ., 15, 15 (1923). a THISJOURNAL,16, 273 (1923). 4 Biochem. J . , 17, 410 (1023). 1
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3 minutes. It required 5 to 10 minutes to water the various lots of cans, which were then passed through an exhaust box at a temperature of about 95' to 99' C. (200' to 210' F.). This required 4 to 5 minutes and the cans were then sealed. The experimental pack thus prepared was divided into lots processed as follows: Lot 1 2 3 4 5 6
Time Minutes 30 60 15 30 45
30
-Temperature-
c.
100 100 115 115
115 126
(" F.)
.
(212) (212) (240) (260
These cans were then shipped to Columbia University laboratory and there used for feeding tests after the routine established by Sherman, La Mer, and Camphel16 for scurvy testing. Two sets of control animals were used. One group received the basal diet alone and died from scurvy in about 30 days. The second control group received 1 gram of raw cabbage per day plus the basal diet. These animals grew normally and a t the end of 80 days were still free from any symptoms of scurvy. A point in regard to the second control group should be noted. For purposes of accurate comparison, an attempt was made to use throughout the 80day period cabbage taken from the lot that was canned. This was kept in the cellar room in the university. The feeding experiments were b e u n about December 1and about January 10 it was found that 1 gram per day of this lot began to lose potency. The outer leaves were wilted, but the inner leaves, which were fed, seemed crisp. However, by substituting fresh cabbage obtained in the market a potency was secured from 1 gram. The writers interpret this to mean the destruction of the vitamin in storage. Zilva's experiments4 showed that in the presence of air decitrated lemon juice made pH 12.5 in reaction lost nearly 80 per cent of its tiitamin C content a t room temperature in half an hour. It might well be expected that cabbage with pH of 5.6, even a t a lower temperature, would suffer considerable vitamin C destruction if air was not excluded. A third control group, representing a series of animals t o which were given 20 grams daily of open-kettle cooked cabbage (cooked 45 minutes a t 100' C.), is included in the chart. The feeding experiments fall into several series. The first series were fed 40 grams, 30 grams, and 20 grams daily of the canned cabbage weighed on a raw basis. It soon became evident, however, that these amounts were in excess of what was needed for protection, and after 40 days the 6
J . A m . Chem. Soc., 44, 165 (1922).
January, 1924
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
40-gram series was changed to 15 grams daily. At the end of 80 days all these animals were still actively growing, and after chloroforming and autopsying no trace of scurvy could be detected. It follows that the commercial canning process, even at temperatures of 115" to 126' C. (240' to 260" F.), is no more destructive than home cooking. A second series was then begun, in which 5, 10, and 15-gram amounts daily of cabbage processed 60 minutes at 100" C. (212" F.), 45 minutes at 115' C. (240" F.), and 30 minutes at 126" C. (260" F.) were used. This test was limited to 46 days, by the exhaustion of the canned material but at this time growth was normal and continuous and the autopsied animals showed no trace of scurvy. I n the final series 2, 4,and 8-gram daily feeding3 of cabbage processed 30 minutes at 115" C. (240' F.) and 30 minutes at 100" C. (212' F.), respectively, were used. This series demonstrated that 2 grams was inadequate as a protection against scurvy, and that 4 grams daily was very close to the protective limit, protecting over a period of 70 days. The 8-gram amount, as expected, proved completely protective. When one reaches the lower limit in a vitamin C test the conclusiveness of the findings becomes affected by the physical state of the animals, because here resistance to disease, and not, simply growth, is the primary consideration. Such variability manifested itself in the 2-gram series, one of the animals remaining free from scurvy for nearly 70 days on this diet. I n view of the definite results of the 4 and &gram series, however, it seems safe to assume that in the methods used by the writers sufficient protection of the vitamin was secured to justify the feeding of canned cabbage on a ratio of 4 :1 of raw cabbage. CONCLUSIONS
Perhaps the most important fact brought out by the experiments is the lack of influence manifested by variations in temperature and heating times within the range of these experiments. If the temperature and duration of heating are the main factors in the destruction of vitamin C, increased destruction with time of heating and rise of temperature should have resulted. Such increase fails to appear. Four to 5 grams remained the protective dose almost regardless of these variables, and in the case of the 2-gram series the pair on 30 minutes at 100' C . succumbed more quickly than the pair on 30 minutes at 115' C. This does not mean that
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vitamin C destruction is independent of temperature or time of heating, but it is at least suggestive that some other factor is the primary determinant in case of canned products. So far, then, as the evidence of the foregoing experiments goes, they show that canning as qarried out commercially and at the temperatures and times cited actually produces less vitamin C destruction than did the open kettle cooking. Do they indicate that this difference is due to superior vitamin content .of the freshly harvested product used for canning or to the protection afforded by sealing the product in the cads before heating? The writers are now conducting experiments, soon to be reported, in which the food is cooked with variable amounts of oxygen. The canning process offers methods of hermetical sealing which permit placing a definite quantity of oxygen in the can and holding this amount fixed throughout the heating processes. In this way the writers hope t o evaluate the effect of varying amounts of oxygen on vitamin C under constant temperature and duration of heating.
Simple Device for Sodium Flame' By Jacob Dolid MCGILLUNIVERSITY, MONTREAL, CANADA
The arrangement shown on the sketch was found especially suitable for use in class laboratory work in polariscopy. The steady, bright flame that can be obtained also makes it useful for more precise work. The sketch. is perhaps selfexplanatory. The asbestos tube may be made conveniently by wrapping a piece of asbestos paper loosely around the burner tube and twisting two strands of platinum wire around the asbestos t o keep it in place. Before using, it is necessary to have the asbestos wetted with solution to the top. Once started, a steady, yellow flame may be maintained as long as there is salt solution in the reservoir. 1
Received November 23, 1923.
