Defects and spoilages of processed seafood products:

• Blue discoloration is a known defect in canned crab and lobster meat caused by the oxidation and complexation of hemocyanin copper with ammonia.
• Curding is a defect in canned salmon and tuna where coagulated sarcoplasmic proteins precipitate as an unsightly white curd on the surface of the fish.
• Dun spoilage is an aerobic fungal spoilage specific to salted and dried fish, caused by the halophilic xerophilic brown mould Sporendonema epizoum (Wallemia sebi) forming pepper-like dark brown/black spots on the surface. Because it is an obligate aerobe that attacks low-moisture dried products, it cannot occur inside commercially sterile, hermetically sealed canned products.
• Struvite formation is a defect in canned fish/crustaceans where magnesium ammonium phosphate crystals ($MgNH_4PO_4\cdot 6H_2O$) precipitate resembling broken glass.