Subtopic: Heat and Mass Transfer in Food Processing
Question Statement:
In food freeze-drying (lyophilization), moisture is removed by which physical process?
Options:
(A) Sublimation of ice directly into water vapor under deep vacuum ($P < 611\text{ Pa}$, below the triple point of water)
(B) Atmospheric boiling
(C) Centrifugal separation
(D) Chemical absorption by lime
Answer Key:
A
Step-by-Step Solution & Explanation
Maintaining system pressure below water's triple point ($611.65\text{ Pa}, 0.01^\circ\text{C}$) enables solid ice to sublime directly into vapor without entering the liquid phase, preserving food matrix porosity.