II. REMEDIAL TREATMENTS 



Before a comprehensive study could be under- 

 taken to prevent blueing, we first had to be 

 able to produce the condition in the laboratory 

 since its natural occurrence was unpredictable. 

 We were able to do this in the preceding ex- 

 periments and now we could move on to the 

 area of preventive measures. 



A. Addition of Organic Acids 



The literature suggested that various organic 

 acids would prevent blueing of crab meat. We 

 had determined that increasing the pH would 

 influence the degree of blueing slightly. We 

 proceeded to add dilute solutions of the follow- 

 ing acids to cans of crab meat containing iron: 

 citric acid, ascorbic acid, lactic acid, and tar- 

 taric acid. The crab meat was processed and 

 examined as previously described. Results are 

 shown in Table 3. 



Table 3. — Results of adding organic acids to canned 

 crab meat to prevent blueing. 



Additive 



Concentration 



Visual 

 rating^ 



Citric acid 



Ascorbic acid 

 Lactic acid . . 

 Tartaric acid . 



Ferrous ammonium 

 sulfate 



2% 

 3% 

 5% 



1% 

 3% 



1% 

 3% 



1% 

 2% 



0.005 M 





 



-(-+++ 



+4-1-+ 



++++ 

 +++ 



Distilled water 

 (control) . . . . 



' ^ no visible blueing 

 + = very slight blueing 

 ++ ^ slight blueing 

 +++ = moderate blueing 

 + 1 1 1 = heavy blueing 



Results shown that when a 3' 

 citric acid brine solution were added to the cans, 

 no blue discoloration occurred even in the pres- 

 ence of iron. A 2Sr citric acid solution, how- 

 ever, allowed some discoloration to develop. Un- 

 fortunately, a 2, 3, and 5 ^c citric acid solution 



imparted a very unpleasant flavor to the crab 

 meat. Varga, Dewar, and Anderson (1969) 

 reported that the association between the con- 

 centration of citric acid added and the appear- 

 ance of blue discoloration in crab meat bore a 

 statistically significant inverse relationship. A 

 I'^r and 2Cr solution of tartaric acid did not 

 completely prevent blueing. Both concentra- 

 tions seemed to be about as eff'ective as the 2% 

 citric acid solution. Lactic acitl and ascorbic 

 acid appeared not to prevent blueing. 



These results indicated that a lowering of 

 the pH contributes, at least in part, to the ef- 

 fectiveness of citric acid in preventing blueing. 

 Citric acid, however, is also known for its anti- 

 oxidant eifect and chelating ability. Ascorbic 

 acid is a good antioxidant but proved useless 

 in the above experiments. We decided to de- 

 termine if chelation of essential metal ions by 

 citric acid produced the anti-blueing effect by 

 experimenting with other chelating agents. 



B. Addition of Chelating Agents 



Ethylenediaminetetraacetic acid (EDTA) 

 and several of its salts have proven eff'ective 

 in chelating troublesome metal ions such as 

 magnesium, iron, copper, etc. Since we had 

 found earlier that iron was responsible in part 

 for blue discoloration, we thought that this 

 group of compounds might prove beneficial in 

 correcting the blue discoloration. The diso- 

 dium salt of EDTA is already approved by the 

 Food and Drug Administration for use in veg- 

 etables, fruits, and dressings. The calcium di- 

 sodium salt is approved for use in several sea- 

 foods, vegetables, soft drinks, and dressings. 

 The following experiment was conducted using 

 various salts of EDTA. 



Disodium EDTA, disodium calcium EDTA, 

 and tetrasodium EDTA, at a level of 250 ppm 

 in brine, were added to cans of crab meat con- 

 taining iron. The 250 ppm level was selected 

 because this is the present upper allowable 

 limit of any salt of EDTA. The cans were 

 processed, stored, and examined after 3 days. 

 The results showed that no diflference in the 

 intensity of blueing occurred between the var- 

 ious salts of EDTA and/or between the salts 

 and the control. It is not entirely clear why 

 EDTA salts did not deter blueing. It is known, 

 however, that the eff'ectiveness of EDTA in 



