I N D U S T R I A L A N D ENGINEERING CHEMISTRY
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Biological Values of Certain Types of Sea Food’ 11-Vitamins in Oysters (Ostrea virginicu)z D. Breese Jones, J. C. Murphy, and E. M. Nelson PROTEIN
A N D h7UTRITION
DIVISION,BUREAU O F CHEMISTRY AND
SOILS,
WASHINGTON,D.
c.
Fresh Chesapeake oysters were ground in a frozen age8 shows that in certain condition to a homogeneous consistency, and preserved able on the biological cases, depending on the seain this state throughout the period of experimentation. value of sea food, parson and locality, oysters live Experiments with albino rats showed that oysters are ticularly shell fish. There is a l m o s t exclusively on dia good source of vitamins A, B, and D. atoms. probably no class of food of Two grams (0.32 gram on a dry basis) of oysters furBut little work has been equal importance that has re. nished sufficient vitamin A to cure rats of xerophthalpublished heretofore on viceived such scanty attention mia. tamins in oysters. Randoing from the standpoint of its Tests made by the curative method showed that 3.5 found that guinea pigs fed a general nutritive properties. grams (0.56 gram dry basis) of oysters contained nearly vitamin C-deficient diet supI n former years shell fish were enough vitamin B to supply the needs of young rats. plemented with 15 grams of prized chiefly because of their For long-continued normal growth, however, a little oysters daily maintained their delicate and appetizing flavor. more than 5 grams (0.8 gram dry basis) was required. weight for 6 weeks and did Modern discoveries in the Five grams of oysters given to rachitic rats daily for not develop scurvy. Later field of nutrition, particularly 10 days induced slight calcification of the long bones, Malcolm,10 working w i t h with reference to vitamins comparable in degree with that produced in the same etnereal extracts of oysters, and to the part played by cerlength of time by 4 mg. of good cod-liver oil. The same was unable to detect the prestain mineral constituents-as daily quantity of oysters induced about half calcificaence of any vitamin A. calcium, phosphorus, iodine, tion in 15 days and complete calcification of the rachitic T h e o y s t e r s used in the iron, and other elements-in metaphyses in 20 days. work described herein were their relation to such diseases Oysters were found deficient in the factor required fIesh, medium-sized, Chesaas rickets, goiter, and anemia, for reproduction and rearing of young. peake oysters purchased on suggest that oysters may have Dehydration at 40’ C. under reduced pressure (10 t h e Was hi n g t on market. m a r k e d food values aside to 15 m m . ) was found to inactivate to a great extent They were obtained for the from their gustatory propervitamins A and B in oysters. greater part during the winties. O y s t e r s constitute the ter. For reasons hereinafter most valuable fishery product of the United States. The stated, the oysters were frozen as soon as possible, ground, annual yield in this country is about 30 million bushels, with and kept in the frozen condition during the periods of experimentation. Estimation of vitamins A, B, and D in the a return to the fishermen of nearly 15 million dollars. This article is the second of a series of studies projected frozen oysters, made by means of feeding tests with albino by the Protein and Nutrition Division of the Bureau of Chem- rats, showed that, on a dry basis, the oysters used conistry and Soils on the biological properties of shell fish from tained these vitamins in proportions that compare favorably the standpoint of their vitamin content and the nutritive with those of other foods that are highly regarded as sources of these dietary accessory factors. quality of their proteins.2 During the course of the work some evidence was obtained The subject of vitamins in oysters has a twofold interest, as has been recently pointed outs in a general preliminary suggesting that there may be a seasonal variation in the survey of the results of work done in this laboratory on the vitamin content of oysters. This phase of the subject is vitamins and proteins of oysters, clams, and shrimp. I n now under investigation. It was found that fresh oysters dehydrated at a low temthe first place, oysters constitute an important and extensively used item of food; any additional information regard- perature under reduced atmospheric pressure had lost nearly ing their food value is therefore desirable. I n the second all their original vitamin B properties and a very significant place, the material upon which oysters feed consists largely proportion of those of vitamin A. This loss of vitamin propof diatoms and minute organisms, marine forms of life to erties during dehydration was attended by other changes which have been t r a ~ e d 4 ~ ’the origin of the fat-soluble of a chemical nature. The possible reasons for the destrucvitamins found so abundantly in certain fish-liver oils, such tion of these vitamins under such mild treatment are disas that of the cod. I n a comprehensive review of work cussed elsewhere. done by numerous investigators on the food of oysters, SavVitamin B
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A preliminary report of this work, 1 Received September 14, 1927. which was started in the fall of 1924, was read at the meeting of the Society for Experimental Biology and Medicine held in New York, April, 1926. An abstract of this paper was later published in Proc. Soc. E x p f l . Bid. Med., 23, 519 (1926). The first article of this series was published under the title “Nitrogen Distribution and Percentages of Some Amino Acids in the Muscle of the Shrimp, Peneus seliferus (L.),” Jones, Moeller, and Gersdorff, J . B i d . Chem.. 65, 59 (1925). 8 Jones, A m . J. Pub. Health, 16, 1177 (1926). 4 Hjort, Proc. Roy. SOL.(London), B93, 440 (1922). 8 Coward and Drummond, Biochem. J . , 15, 530 (1921). I Jameson, Coward, and Drummond, I b i d . , 16, 482 (1922). 7 Drummond and Zilva, I b i d . . 16, 518 (1922).
CURATIVEMETHOD-In the curative tests for vitamin B young albino rats weighing from 45 to 55 grams were fed the vitamin B-free basal ration indicated on the charts. When a decided decline in the weight of the animals had occurred as a result of vitamin B deficiency in the diet, the material to be tested, with one or two exceptions, was fed at definite levels daily apart from the basal ration. Osborne 8 Fishery Investigations, Series 11, H. M. Stationery Office, London, 8, No. 1 (1925). 9 Compt. rend., 177, 498 (1923). 10 Trans Pror N e w Zealand Ins!., 56, 650 (1926).
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and Mendel's salt mixture was used in all the diets except the rachitic diet. The rats were kept in cages having raised screen bottoms to prevent them from having access to their excreta. Dehydrated Oysters. In the first experiments a product prepared by dehydrating fresh oy8ters a t a temperature not exceeding 40-45" C., and at 10 to 15 mm. atmospheric pressure, was used. This usually required about 30 hours. The product was dark colored, and its odor and general properties indicated that during the process of dehydration chemical changes had taken place. The dry residue was ground to a powder. When this product was fed, separate from the basal diet, difficulty was encountered in getting many of the rats to eat all the daily portions allotted to them. The dehydrated oysters were fed in daily doses of 0.25 and 0.5 gram. As can be seen from the growth curves in Chart I, 0.25 gram merely retarded, but did not arrest, the decline in weight of the animals. Fed a t a daily level of 0.5 gram, the weight decline was arrested, followed by a slow growth for about 2 weeks with subsequent loss of weight. Another lot of rats was fed the oyster meal incorporated in the basal diet a t a 7 per cent level. Based on their average food consumption, this quantity of oysters in the diet furnished approximately a daily intake of 0.5 gram of dehydrated oysters. The results, as shown on Chart I, indicate the presence of but little vitamin B. The quantities of the dehydrated product fed, 0.25 and 0.5 gram, represent 1.5 and 3.1 grams, respectively, of fresh oysters. Compared with the results obtained later (Charts I1 and 111) with fresh! frozen oysters, the vitamin B content of the dehydrated product was decidedly less than that of the fresh oysters, indicating that during the process of dehydration there was some destruction of vitamin B.
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room. I n this way a homogeneous product was obtained of which uniform samples could be weighed. It has been previously shown that freezing temperatures have no appreciable effect on vitamins.ll The rats eagerly ate the quantities of the frozen oysters that were daily allotted to them. Estimations of the vitamin B content of the frozen oysters were made both by the curative and by the prophylactic methods. In the experiments made by the curative method, different lots of rats, after having been fed the vitamin B-
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[VITAMIN B IN DEHYDRATED OYSTERS
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Chart I
Raw, Frozen Oysters. On account of changes that took place in the oysters during dehydration and the apparent i?jurious effect upon vitamin B, it became necessary, in order to get data from which the vitamin B content of fresh oysters could be fairly evaluated, to devise a method which, without impairment of the vitamin, would yield a palatable product having uniform composition, and which could both be kept without deterioration throughout the period of experimentation and be satisfactorily weighed out in the desired quantities for the daily feeding. This was accomplished by separating the liquor from the fresh oysters as far as possible by draining in cheesecloth, and placing the oyster meats in a cold-storage room a t a temperature below freezing. The frozen product was then finely ground in a meat grinder which had been cooled to the temperature of the freezing
free basal ration until a marked decline in weight had resulted, were given the oysters daily in quantities of 1, 2, 3.5, and 5 grams. The r e d t s are presented in Charts I1 and 111. I n all cases the decline in weight attending the preliminary period was promptly arrested. With 5 grams of oysters growth followed a t an excellent and uniform rate for 4 weeks. Growth a t a somewhat slower rate resulted with the 3.5-gram portions, whereas with 2 grams of oysters daily the animals grew a t a fair rate for about 3 or 4 weeks, with a tendency to decline in weight thereafter. A slow rate of growth for 2 or 3 weeks followed the administration of 1 gram of oyster, followed by a decided decline in weight. These results indicate that 3.5 grams of oysters daily are nearly sufficient to provide the quantity of vitamin B necessary for the normal growth of young rats. PROPHYLACTIC METHoD-Although results obtained with young animals by the curative method give a fair idea of the vitamin content of the substance under examination, this method does not allow so rigorous a test as does the prophylactic method continued over a much longer period of time and covering most of the growing stage of the animal. A quantity of substance that would furnish enough vitamin to stimulate a young animal's recovery from vitamin starvation, and to grow thereafter a t an excellent rate for 3 or 4 weeks, may not be adequate to supply the animal's need throughout the greater part of its normal growth period. In order to check the results obtained by the curative method, four lots of young rats weighing from 45 to 50 grams were fed the basal diet supplemented by 1, 2, 3.5, and 5 grams of frozen oysters daily. The results of these tests are shon-n in Charts IV, V, and VI. One gram daily enabled the animals to do but little better than the controls on the vitamin B-free diet. With 11
Jones, Murphy, and Moeller, Am. J . Physiol., T i , 265 (1925).
INDUSTRIAL AA’D ENGINEERING CHEMISTRY
February, 1928
i ~ l l VITAMIN l I IATPOINTS
B IN OYSTERS
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MARKED”X*EGMS RAW OYSTERS GIVEN
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I l l I 1
DAILY
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SALTS
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W T E R FAT STARCH
5 1) 15 **
Chart IV
VITAMIN B IN OYSTERS 3.5 GM. DAILY
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BUTTER FAT 15 STARCH 60
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VITAMIN B IN OYSTERS
TWO GRAMS DAILY
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ONE GRAM DAILY
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Chart V
Chart VI
2 grams a slow rate of growth for about 60 days resulted, followed by a decline. Growth a t a satisfactory rate for about 9 weeks attended the administration of 3.5 grams of oysters. After that the rate of growth was more or less retarded. It is of interest to note that as tested by the curative method (Chart 11),5 grams of oysters daily appeared to supply sufficient vitamin B to meet growth requirements of young rats. Tested by the prophylactic method, however (Chart IV), the same quantity of oysters, although enabling the animals to grow a t an excellent rate for about 60 days, yet failed to maintain growth a t that rate for a longer period. After about 12 weeks the animals suffered a rapid decline in weight. That this decline was caused by an insufficient amount of vitamin B was shown by the prompt resumption of growth following substitution of 0.4 gram of yeast12 daily for the 5 grams of oysters. A comparison of the results obtained by the curative and the prophylactic methods shows that the latter method disclosed a degree of vitamin deficiency that could not have been detected by the results obtained by the curative method. The frozen oysters used in these experiments contained 84 per cent of water. The various quantities fed-namely, 1, 2, 3.5, and 5 grams-therefore represent 0.16, 0.32, 0.56, and 0.80 gram, respectively, of dry material. On this basis oysters compare favorably as a source of vitamin B with foods which are recognized as excellent sources of this dietary factor.
I n view of the apparent ease with which vitamin B was destroyed during the process of dehydration, the effects of cooking upon the vitamin B content of oysters was studied. A lot of fresh oysters was divided into two portions. One portion was immediately frozen, and the other was heated for about 2 hours in closed glass jars in boiling water. The cooked portion was then frozen. Estimation of the vitamin B content of both portions carried out in parallel feeding tests with 2 grams of the oysters daily showed that the cooking had produced a small decrease in the vitamin content of the oysters.
1’ The yeast used in these experiments was furnished by the Northwestern Yeast Company, through the courtesy of M. H.Givens.
Vitamin A
The estimation of vitamin-4 was carried out by the curative method. Young rats were fed the vitamin A-free basal ration indicated on the charts untiI well-developed symptoms of xerophthalmia had resulted Portions of the material to be tested were than given daily, and the effect on the condition of the eyes was noted. Vitamin B was supplied daily by 0.4 gram of yeast given in the form of tablets, prepared in the laboratory. Dehydrated Oysters. Experiments with dehydrated oysters fed daily in quantities of 0.25 and 0.5 gram indicated the presence of little or no vitamin A. I n practically all cases where the portions fed were eaten there was a definite growth response, which continued a t a fair rate for 30 days or longer. There was, however, no noticeable improvement in the ophthalmic condition of the animals. The temporary growth response noted is probably to be ascribed to the growth-promoting property of the more stable vitamin
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D, which is present in significant quantities in fresh, raw oysters. That vitamin A was demonstrated to be present in notable amount in raw, frozen oysters shows that this vitaniin, like vitamin B, was detrimentally affected by the process of dehydration. Raw, Frozen Oysters. The frozen oysters were fed a t levels of 3.
