present in the nonprocessed discarded crabs. 

 We concluded that processing dead crabs, in 

 itself, was not the cause of blueing. How- 

 ever, it is possible that this condition is con- 

 tributing when other factors are present. 



B. Processing Hypothesis 



Plant conditions and/or methods of prepar- 

 ing crab meat for canning vary from plant to 

 plant. For example, one processor may use 

 a parchment liner while another may not. 

 Commercial methods for obtaining a vacuum 

 are (1) mechanical evacuation of the air prior 

 to sealing the cans and (2) heating the open 

 cans prior to sealing. Another variable is the 

 composition of the inplant water as water in 

 the coastal areas sometimes contains high levels 

 of minerals that could affect the processed prod- 

 uct. These variables were examined to de- 

 termine if they contribute to the blueing prob- 

 lem. Figure 1 describes the experimental 

 design. 



1. Effect of parchment liners. — Approxi- 

 mately 40 cans of crab meat were prepared 

 and divided into two lots. Parchment liners 

 were added to the first lot while the second 

 lot without liners served as the control. The 

 cans of crab meat were then processed. Exam- 

 ination of the two lots after 3 days of storage 

 revealed no difference in color between the two 

 lots. 



2. Effect of method of obtaining a vac- 

 uum. — Cans of crab meat were prepared as 

 in experiment 1 above and the two lots were 

 further divided into two lots each, making a 

 total of four lots (Fig. 1) . Two lots (with and 

 without parchment liners) were processed 

 using mechanical means for vacuum production 

 while the second two lots were heated to 140° F 

 prior to sealing the cans in order to produce 

 the vacuum. Examination of the stored prod- 

 uct showed no discoloration in any of the lots. 



3. Effect of plant water used in process- 

 ing. — An experiment was conducted whereby 

 water from three sources was used in process- 

 ing crab meat. A brine solution was made 

 from (1) water used in the plant where the 



crab meat was picked (primary), (2) water 

 used in the canning plant where the blueing out- 

 break occurred (secondary), (3) Pascagoula 

 city water (known to contain a high level of 

 certain minerals), and (4) a distilled water 

 control. Cans of crab meat were prepared as 

 in experiment 2 (four lots) with each lot being 

 further divided four ways. Brine solutions pre- 

 pared from the various water sources were ad- 

 ded as shown in Figure 1. The cans were pro- 

 cessed, stored, and examined as before. No dif- 

 ference in color existed among the different lots. 

 We concluded that the use of parchment lin- 

 ers, the method used to produce vacuum, and 

 the source of the processing water did not in- 

 fluence the development of blue discoloration. 



C. Chemical Ion Hypothesis 



Many theories have been proposed relative 

 to the role chemical ions play in the blue dis- 

 coloration of crab meat. A majority of the 

 reports found in the literature suggest that 

 copper ions are responsible (Oshima, 1932; 

 Fellers and Harris, 1940; Dassow, 1963; Gron- 

 inger and Dassow, 1964). Others report that 

 iron, ammonia, and sulfur contribute to the 

 problem. 



Heretofore, we had not been able to repro- 

 duce the blueing experienced in the commercial 

 lots. We decided, therefore, to add chemical 

 compounds containing the ions mentioned above 

 to cans of crab meat to determine if the blue- 

 ing could be produced in this manner. 



Dilute solutions of the following compounds 

 were added to cans of crab meat: cuprous 

 chloride [CuCl], cupric nitrate [Cu(N03)2], 

 ferrous ammonium sulfate [Fe(NH4)2(S04)2], 

 and ammonium hydro.xide [NH4OH]. Distilled 

 water was used for the control. Salt was added 

 to the solutions to give the desired brine con- 

 centration. The cans were processed by our 

 commercial method and examined after 3 days 

 of storage. Table 1 shows the results. 



The ferrous ammonium sulfate solutions pro- 

 duced blue discoloration typical of that found 

 in canned crab meat. Neither copper com- 

 pound caused significant blueing nor did the 

 dilute solutions of NH4OH. The control was 

 negative. Thus, the foregoing results showed 

 that one of the ions in Fe(NH4)2(S04)2 was 

 responsible for blueing. 



