Question

A type of freezing where resistance to heat transfer is minimized due to intimate contact between food or package and refrigerant

• A. Indirect contact freezing
• B. Air freezing
• C. Immersion freezing
• D. Fluidized-bed freezing

Hint:

Think about cooling a hot object. Plunging it into cold water (immersion) cools it much faster than leaving it in a cold room (air) or placing it on a cold block (indirect contact). The same principle applies to freezing.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The efficiency of a freezing process depends on how quickly heat can be removed from the food. The rate of heat transfer is maximized when there is direct, intimate contact between the food and the cooling medium (refrigerant), which minimizes the resistance to heat flow.
Step 3: Detailed Explanation:
- Immersion freezing involves directly immersing the food product (either packaged or unpackaged) into a liquid refrigerant, such as chilled brine, glycerol, or liquid nitrogen. This direct immersion ensures complete, intimate contact over the entire surface of the food, leading to a very high rate of heat transfer and rapid freezing.
- Indirect contact freezing (e.g., plate freezing) places food on metal plates cooled by a refrigerant. While contact is good, it's indirect and may not be perfect over the entire surface.
- Air freezing (e.g., blast freezing) uses cold air as the refrigerant. Air is a poor conductor of heat compared to liquids, so the heat transfer rate is lower.
- Fluidized-bed freezing is a type of air freezing where small particles are suspended in air. While it improves upon standard air freezing, the contact is still with air, not a liquid.
Step 4: Final Answer:
Immersion freezing provides the most intimate contact between the food and the refrigerant, minimizing heat transfer resistance. Therefore, option (C) is the correct answer.