Food Process Engineering & Operations

Assertion (A) is completely true: Freeze drying (lyophilization) involves freezing the food followed by drying under high vacuum below water's triple point ($0.01^\circ\text{C}, 611.65\text{ Pa}$), causing ice to sublime directly into water vapor without passing through the liquid phase. Reason (R) is completely false: Freezing preserves food by lowering temperatures to sub-zero levels (typically $-18^\circ\text{C}$ or below) to immobilize water as ice, not by subjecting food to elevated temperatures (elevated temperature in sealed containers describes thermal canning/appertization).

Option analysis:

• Both true: Incorrect because (R) is false.
• Both true: Incorrect because (R) is false.
• is true but (R) is false: Correct statement.
• is false: Incorrect because (A) is true.

In a vapor compression refrigeration cycle, the reciprocating compressor draws in vaporized refrigerant from the evaporator at low pressure and low temperature during its suction stroke, and compresses it to discharge high-pressure, superheated vapor into the condenser.

Option analysis:

• Low: Correct, the suction stroke draws refrigerant vapor directly from the low-pressure evaporator.
• Intermediate: Found only in multi-stage flash chambers, not standard single-stage suction.
• High: State after compression in the discharge line.
• Atmospheric: Cycle operates in a sealed loop independent of atmospheric pressure.

Food irradiation using low-to-medium doses of gamma rays, electron beams, or X-rays is sometimes labeled or referred to in industry and consumer education as 'picowaved' (referencing wavelengths in the picometer range, $10^{-12}\text{ m}$, of gamma radiation, distinguishing it from longer microwave radiation, $10^{-2}\text{ m}$). Standard regulatory labels also mandate the international Radura logo.