Canned Atlantic Crab Meat A New American Food CARL R. FELLERS
STERLING G. HARRIS Blue Channel Corporation, Centreville, Md.
Massachusetts State College, Amherst, Mass.
HE edible blue crab (Callinectes sapidus) is by far the most important and abundant crustacean on the Atlantic and Gulf Coasts of the United States. A catch of 73,501,000 pounds in 1936 was announced by the United States Bureau of Fisheries. This is equivalent to about 11,000,000 pounds of picked crab meat worth at retail at least $5,000,000. Until 1938 the only forms in which the crab meat had been marketed in this country were as fresh-cooked and frozen meat. Aside from 130,000 pounds of canned Pacific Coast Dungeness crab meat (Cancer magister), the only canned crab now sold in the United States is of Japanese origin. In 1937 this imported product reached the huge total of 11,157,000 pounds worth conservatively $5,000,000. Because of the practical absence of a competing domestic crab canning industry, only a small tariff is collected on the Japanese product. It is hoped that the new canning process described in this paper will make our country largely independent of Japanese crab imports. The Japanese meat comes from the large king crab of Siberian waters (Puralithodes cclmtschaticu). There
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are no serious technical difficulties in the canning of either Japanese or Pacific Coast crabs. However, the small supplies of the latter preclude extensive canning developments. The so-called fresh-cooked Atlantic crab meat is obtained simply by cooking the live crabs in steam or water and removing the meat from the claws and body by hand. Without further treatment the meat is filled into perforated unsealed cans, packed in crushed ice, and thus marketed in cities close to the Atlantic and Gulf seaboards. Since the fresh crab meat is grossly contaminated (5,8)during picking and p r e p s ration, and since it is not subsequently sterilized, the meat is a strictly perishable product and must be consumed in a few days a t most. Thousands of pounds of this fresh meat have been seized and destroyed on our markets in a semidecomposed condition by the Federal Food, Drug and Cosmetics Administration ( l e ) . Thus, the market for the fresh product is limited and the quality often questionable. Lately, a small volume of frozen crab meat has been successfully marketed. 592
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A successful method of canning the Atlantic blue crab is described. The method consists essentially in stabilizing the copper present in the hemocyanin of the crab's blood and flesh by means of a protective brine dip containing small amounts of aluminum and/or zinc salts. The canned meat of the blue crab contains about 18 per cent of high-quality protein; it is low in fat and high in ash content. Particularly notahlc is the high content of essential minerals such as calcium, phosphorus, iron, copper, and iodine. The iodine content is from 400-500 parts per billion. The meat contains moderate amounts of thiamin and riboflavin and a small amount of ascorbic acid. The technique rnakcs possible the establishment of an American crab canning industry and introduces a new attractive, tasty, and nutritious seafood to the American consumer.
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been fully worked out. The problem a t hand was to control or stabilize these complex reactions. After studying the problem seasonally for nearly 5 years, the use of a protective salt treatment gave the desired result. The canned meat must retain its fine white color and full flavor in order to equal the fresh product in quality and attractiveness. The protective dip consists of a sodium chloride brine containing sufficient lactic acid to keep the pH of the brine slightly below the neutral point, together with the protective chemical itself. The process makes use of salts of aluminum and/or zinc in small amounts (less than 400 p. p. m.). Aluminum is prcferred to other metallic salts because it presents no healtlth hazards and its use is free from official or popular objection, provided its presence is declared on the label of the container. The aluminum remaining in the meat itself does not exceed 0.04 per cent and is therefore of no health significance. Careful correlation of practical aud laboratory observations showed that the solution of the problem lay in (a) selection of crabs as to season, time of molt, sex, and locality, (6) improved methods of handling and mcat removal, (c) use of the protective dipping brine, and (d) a thermal treatment which must be sufficient to kill all microorganisms present but which does not overcook or otherwise injure the delia t e flavor of the meat. Although one detail is as important as the other, the real heart of the new process lies in the protective brine dip. The sequence of operations in the cannery is to steam the live crabs in order to coagulate the protein and loosen the carapace and visceral tissues sufficiently so that they can be removed; to eviscerate and wash; to dip in the protective brine and drain to remove any added water; to 6ll into parchment-lined cans and seal under high vacuum; and finally to give a thermal treatment of 250" F. for 30 minutes for 6.5ounce flat cans. The csnned product is of two kinds-that is, the white flakes and the brownish claw meat. Both are of equally good flavor but are more attractive when not packed together in the same container. The canned product retsins its original attractiveness and flavor indefinitely. The fimt plant to pack American Atlantic crab meat is now in operation a t Port Royal, S.C., and others will be opened on the Chesapeake Bay and on the Gulf of Mexico. Although indiscriminate taking of crabs will decrease the supply, it is hoped that appropriate conservation measures
Though numerous attempts (7, 9, 11) had been made to can the meat of the blue crab so aa to preserve i t indefinitely and thus widen the distribution, these metbods had not been successfully adopted by industry. The main difficulty has always been serious color and flavor changes in the canned rncat. These changes result largely from the breakdown nf the rather unstable proteins under the influence of heat. For example, both ammonia and volatile sulfur compounds are liberated in the meat during the canning process. The crab's blood contains hemocyanin, a compound analogous to the hemoglobin of mammals' blood, in which copper replaces the iron of the hemoglobin. The blood contains about 60 parts per million of copper, and copper is always present in the flesh in amounts varying from 5 to 25 p. p. m. The amount seems t o vary with the season, with the state of the molt, and in accordance with handling methods. The copper is present in sufEcient amount to react with the other constituents of the meat, such BS ammonia, to form blue copper-ammonia complexes, and to some extent with the sulfur to form snllide. The copper linkage is loose and the metal is readily liberated. In the reduced form, hemocyanin is colorless; in the oxidized form, i t is blue. As Conant, Chow, and Schoenbach ( 1 ) showed, hemocyanin has a high potential and the copper is present in the cuprous state. Some of the remedial measnres taken have been dcscribed by Fellers (5) and by H a m s (6). The exact natureofaomeofthereactinnsoccurrinrZinthe meat during the eanning process have not REmam IN WEICE SEALED CANS ARE GIVENA FINAL TaEaWL TaEnTmNT
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will be taken by the Federal Government and the several states to regulate the industry so that the present adequate crab supply will be perpetuated.
Composition and Nutritive Value A preliminary study was made by Watson and Fellers ( I S ) in 1936. Earlier Fellers and Parks (4) had reported on the chemical composition and other characteristics of Pacific Coast crabs. A few mineral and iodine analyses have been made by Coulson ( 2 ) and by Kilson and Coulson (10). Representative data are reported in Table I. The protein content is high and of apparently high quality, inasmuch as young rats on a diet containing 9 per cent protein from crab meat made average weight gains of 5 grams a week for a 6week feeding period. The crab meat was used in this experiment as the sole source of protein in the diet.
TABLEI. ANALYSIS OF CASNEDBLUECRABMEAT Composition, yo------,-hlineralcontent, P . P M.Moisture 79.00 K 1880 * Dry matter 21.00 Ca 1330 Protein ( N X 6.25) 18.00 hI g 120 Total ash 22.20 20 P380 Ether ext. ifat) n0 . 4400 F zn (fat) FeP 20 Ext. mati matter (by difference) 0.40 cu 13 Ca1./100 grams 77 I 0.46 Alkalinity of ash 11.7 Vitamin Content per 100 Grams 0.012 mg. (24 I. I.?.) Ascorbic acid Thiamin 230 T (70 I. U.) 150 y (60 Bourquin-Sherman units) Riboflavin ~~
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One of the chief sources of interest in this food lies in its high mineral value-calcium, iron, copper, and iodine. The iodine content is among the highest ever reported for any food. The high alkalinity of the ash is likewise notable. The crab meat is a moderately good source of vitamins B1 (thiamin) and BQ (riboflavin) and also contains a small amount of vitamin C (ascorbic acid).
Literature Cited Conant, J. B., Chow, B. F., and Schoenbach, E. B., J . Biol. Chem., 101, 463 (1933).
Coulson, E. J., U. S.Bur. Fisheries, Investigational Rept. 25, 3 (1935).
Fellers, C. R., U. S.Patent 2,155,308 (Jan. 7, 1936). Fellers, C. R., and Parks, C. T., Univ. Wash., P u b . Fisheries, 1, No. 7, 145 (1926). Harris, M. M., Am. J . H y g . , 15, 260 (1932). Harris, S.G., U. S.Patent 2,155,308 (April 18, 1939). Howe, D. W., Ibid., 1,927,123 (Sept. 19, 1933). Hunter, A. C., Am. J. Pub. Health, 24, 199 (1934). Jarvis, N. D., Canner, 83, No. 13, 9 (1936). Nilson, H. W., and Coulson, E. J., U. S. Bur. Fisheries, Investigational Rept. 41, 6 (1939).
Oshima, K., U. S. Bur. Fisheries, Investigational Rept. 8, 6 (1931).
U. S. Dept. Agr., Notices of Judgment under the Food and Drugs Act, 1936-39. Watson, V. K., and Fellers, C. R., Trans. A m . Fisheries Soc., 65, 344 (1935). PRESENTED before the Division of Agricultural and Food Chemistry a t the 98th Meeting of the American Chemical Society, Boston, Mass. Contribution 353 of the Massachusetts Agricultural Experiment Station.
Behavior of Ovomucin in the Liquefaction of Egg White A. K. BALLS AND SAM R. HOOVER Bureau of Agricultural Chemistry and Engineering, U. S. Department of Agriculture, Washington, D. C.
No evidence has been found for the existence of active or activatable proteinase in egg white. The liquefaction of egg white is not accompanied by a diminution of the amount of ovomucin present. VOMUCIN occurs in the thick white of hens’ eggs in far higher concentration than in the thin white, according to McNally (11). He found that the mucin nitrogen is 5.7 per cent of the total nitrogen of the thick white and 0.66 per cent of the total in the thin. We have found that removal of this protein from the thick white gives a watery solution of low viscosity that still contains about 95 per cent of the protein initially present. It is therefore probable that the ovomucin is responsible for the characteristic properties of thick as opposed to thin white. From previous work in this laboratory (6) it was concluded that the breakdown of the thick white is caused by proteolysis of the mucin by a tryptic type of enzyme naturally occurring in the egg white. This conclusion was disputed by van Manen and
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Rimington (12) who were unable to demonstrate proteolysis in the thick white, and confirmed by Hughes, Scott, and Antelyes (9). In view of these conflicting results the problem of the liquefaction of zgg white has been reinvestigated in this laboratory for the past three years. Attempts to demonstrate proteolysis by using a variety of methods were unsuccessful. The few positive results obtained were of small magnitude, little more than the limits of error of the various methods. A study of the method used in the original work (titration with sodium hydroxide in hot alcoholic solution according to FVillstatter and WaldschmidbLeitz) showed that the precipitation of the egg white in the hot alcohol trapped appreciable quantities of the ammonia-ammonium chloride buffer used. The precipitate was much more finely divided in the aliquots incubated for some minutes with the buffer solution and did not render so much of the buffer nontitratable. Therefore titration values were increased by incubation. This result explains the apparent proteolysis observed by Balls and Swenson (5) and by Hughes et al. (9). It is also consistent with the negative findings of van Manen and
