eliminating certain metal ions depends on (1) 

 the pH of the system and (2) the order of 

 complexation of the metals present. 



C. Addition of Buffer Solution 



As mentioned earlier in this paper, one of the 

 companies whose product was affected in the 

 blueing outbreak in the summer of 1969 used 

 a chemical formula to prevent blueing. This 

 preservative was formulated by a consultant 

 and is patented. It consists of a phosphate 

 buffered citric acid solution added with the 

 brine solution. This solution decreases the pH 

 of the canned crab meat to 6.8 or less. 



Our work confirmed that the addition of the 

 company-supplied phosphate-citric acid brine 

 solution to cans of crab meat containing added 

 iron ions prevented blueing. pH thus appeared 

 an all-important factor in blue color inhibition ; 

 however, the chelation of iron ions by citric 

 acid at pH 6.5-6.8 cannot be ruled out. 



D. Extraction of the Blue Colored 

 Complex 



We wished to extract the blue colored com- 

 plex in order to further study the blue phenom- 

 enon. Several attempts were made using 

 organic solvents such as hexane, acetone, chlor- 

 oform-methanol, acetone-chloroform, ether, and 

 trichloroacetic acid (TCA). None of these 

 solvents would extract the complex nor did they 

 affect the color. A dilute solution (0.01 N) 

 of HCl was employed with little success. The 

 acid tended to cause the blue color to dissipate 

 rather than to extract the responsible com- 

 pound. No further attempt was made to study 

 the blueing complex. 



III. NEED FOR ADDITIONAL RESEARCH 



Data obtained during the course of this work 

 probably posed more questions than they an- 

 swered. Although the objectives of this work 

 were achieved, questions regarding the blueing 

 reaction abound: (1) what other condition (s) 

 or compound (s) must be present in addition to 

 iron? (2) is the iron bound and, if so, to what 

 constituent of the crab meat? (3) where does 

 the iron come from? (4) what can be used to 

 extract the color complex in order to better 

 study its formation? and (5) how may the 

 processor avoid the conditions necessary for 

 blueing ? All must be answered if a clear under- 

 standing is to be forthcoming. 



LITERATURE CITED 



DASSOW, J. A. 1963. The crab and lobster fisheries, 

 p. 193-208. In M. E. Stansby (ed.) Industrial 

 fishery technology. Reinhold Publishing Corp., 

 New York. 



FELLERS, C. R., and S. G. HARRIS. 1940. Canned 

 Atlantic crab meat, a new American food. Ind. 

 Eng. Chem. 32: 592-594. 



GRONINGER, H. S., and J. A. DASSOW. 1964. 

 Observations of the "blueing" of king crab, Parali- 

 thodes cmntschatica. U.S. Fish Wildl. Serv., Fish. 

 Ind. Res. 2(3) : 47-52. 



OSHIMA, K. 1932. Studies in crab canning. [U.S.] 

 Bur. Fish., Invest. Rep. 8. 8 p. 



THOMPSON, M. H., and R. N. FARRAGUT. 1969. 

 Problem of "green" frozen raw breaded shrimp. 

 U.S. Fish Wildl. Serv., Fish. Ind. Res. 5. 1-10. 



VARGA, S., A. B. DEWAR, and W. E. ANDERSON. 

 1969. Effect of citric acid on quality of heat pro- 

 cessed crab meat. Can. Fish. Rep. 13: 169-174. 



WATERS, M. E. 1970. Blueing of processed crab 

 meat. 1. A Study of processing procedures that 

 may cause a blue discoloration in pasteurized crab 

 meat. U.S. Fish Wildl. Serv., Fish. Ind. Res. 6: 

 173-183. 



