Question

Rapid rate of drying of fish makes the surface tough and dry which facilitates the escape water from inner layer is difficult is called as

• A. Dehydration
• B. Putty hardening
• C. Case hardening
• D. Pink discoloration

Hint:

To prevent case hardening, the drying rate must be controlled (e.g., maintaining moderate relative humidity and lower initial temperatures) to ensure the rate of surface evaporation matches the rate of internal moisture diffusion.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Drying fish involves removing moisture to lower water activity (\(a_w\)) and prevent microbial spoilage.
However, if the rate of surface evaporation exceeds the rate of internal water migration, drying defects occur.

Step 2: Detailed Explanation:
When fish is dried too rapidly under high temperature and low relative humidity, the moisture from the surface layer evaporates very fast.
This causes the surface proteins to denature and shrink, forming a tough, impermeable outer crust.
This crust is called "case," and the defect is known as case hardening.
Once this dry crust forms, it acts as a barrier that prevents water from the deeper internal layers of the fish from migrating outwards, leaving the interior wet and highly susceptible to bacterial decomposition.

Step 3: Final Answer:
The drying defect described is Case hardening, which corresponds to option (C).