Question

In drying, when water moves from the interior of the food at the same rate as it evaporates from the surface, the surface remains wet. This is known as the

• A. Steady state period
• B. Falling rate period
• C. Constant-rate period
• D. Increasing state period

Hint:

During the constant-rate period, drying rate depends solely on external parameters (air temperature, velocity, relative humidity) and surface remains wet.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Drying kinetics of moist biological materials are divided into distinct drying rate periods based on water transport mechanisms.

Step 2: Detailed Explanation:
During the constant-rate drying period, capillary forces and internal moisture diffusion replenish liquid water at the food surface as fast as it evaporates into the drying air stream.
The food surface remains fully wet, maintaining a constant temperature equal to the wet-bulb temperature of the air.

Step 3: Final Answer:
Thus, this drying stage is known as the constant-rate period.