17
Which of the following statements about freeze-drying (lyophilization) are correct?
(A) .Freeze-drying involves the removal of water through sublimation
(B) .The process of freeze-drying helps in maintaining the structural integrity of the food.
(C) .Freeze-drying is faster than traditional air drying methods.
(D) Freeze-dried products require special packaging to prevent moisture absorption
Choose the correct answer from the options given below:
EXPLANATION
Evaporation & Drying Systems
- Principles of Lyophilization (Freeze-Drying):
- Sublimation mechanism: Water is removed directly from ice to vapor below water's triple point ($\lt 611.65\text{ Pa}, \lt 0.01^\circ\text{C}$).
- Structural preservation: Prevents capillary shrinkage and liquid migration, preserving cellular porous matrix, rehydration capacity, and nutrient integrity.
- Packaging requirement: Freeze-dried foods are porous and hygroscopic; packaging must provide high hermetic water vapor barriers to prevent moisture absorption and collapse.
- Statement C is false: Freeze-drying is an energy-intensive, slow batch process ($12 - 24\text{ hours}$), significantly slower than convective hot air drying.
- Conclusion: (A), (B) and (D) only (Option 2).
Correct option: (2) (A), (B) and (0) only,
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