Question

Which of the following spoilages does not occur in canned products ?

• A. Blue discoloration
• B. Curding
• C. Dun spoilage
• D. Struvite formation

Hint:

Remember that "Dun spoilage" is a fungal infection characterized by brown spots, which only affects dried, heavily salted fish. Canned products are sterile, so they do not support fungal growth like *Wallemia sebi*.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Canning is a method of food preservation in which food is hermetically sealed in containers and thermally sterilized.
Various chemical and biological defects or spoilages can occur in canned seafood due to poor processing, can defects, or chemical reactions.
Detailed Explanation:
Let us analyze the listed types of spoilage to identify which one does not occur in canned products:
- Blue discoloration (A): This is a common defect in canned crab meat and lobsters, caused by a chemical reaction between copper in the hemolymph of the crustaceans and hydrogen sulfide released during processing, forming copper sulfide.
- Curding (B): This occurs during the canning of salmon and other fatty fish when soluble proteins coagulate and form unsightly white curds on the surface of the fish during retort sterilization.
- Struvite formation (D): This is a chemical defect in canned fish (such as tuna and shrimp) where magnesium ammonium phosphate hexahydrate crystals ($\text{MgNH}_4\text{PO}_4 \cdot 6\text{H}_2\text{O}$) precipitate, resembling broken glass fragments.
- Dun spoilage (C): This is a microbial spoilage that occurs exclusively in salted and dried fish products, not in canned items.
It is caused by the halophilic fungus Wallemia sebi (formerly known as Sporendonema epizoum), which grows on the surface of salted fish, forming chocolate-brown or black spots.

Step 2: Final Answer:
Dun spoilage is a defect of salted-dried fish and does not occur in canned products.