Question:
Which of the following methods of ice cream hardening will result in the least hardening time (in hours)?
Which of the following methods of ice cream hardening will result in the least hardening time (in hours)?
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Conductive heat transfer (metal-to-package contact in a plate hardener) is much more efficient than convective heat transfer (air blast), resulting in the shortest hardening time.
Updated On: Aug 7, 2026
- Retail deep freeze cabinet
- Forced draft hardening room
- Domestic deep freeze cabinet
- Contact Plate hardener
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Verified By Collegedunia
The Correct Option is D
Solution and Explanation
Step 1: Understanding the Concept:
Hardening of ice cream is the rapid freezing process that follows draw-off from the ice cream freezer, converting the remaining water into ice crystals.
The speed of this process depends on the heat transfer rate of the hardening method used.
Step 2: Detailed Explanation:
Let us compare the heat transfer mechanisms and typical hardening times of the given methods:
- Domestic and Retail deep freeze cabinets: These systems rely on natural convection of cold air with no forced air movement.
The heat transfer rate is low, and hardening can take up to 12 to 24 hours.
- Forced draft hardening room: These rooms utilize high-velocity cold air (blast freezing at $-30^\circ$C to $-40^\circ$C).
The convective heat transfer rate is high, reducing the hardening time to approximately 4 to 8 hours depending on package size.
- Contact Plate hardener: This system places packaged ice cream directly between hollow metal plates containing circulating refrigerant.
Heat is transferred by direct conduction through the metal plates, which is much faster than convection through air.
This direct contact results in extremely rapid heat extraction, hardening the ice cream in less than 0.5 to 1.5 hours.
Therefore, the contact plate hardener achieves the least hardening time.
Step 3: Final Answer
The correct option is (D).
Hardening of ice cream is the rapid freezing process that follows draw-off from the ice cream freezer, converting the remaining water into ice crystals.
The speed of this process depends on the heat transfer rate of the hardening method used.
Step 2: Detailed Explanation:
Let us compare the heat transfer mechanisms and typical hardening times of the given methods:
- Domestic and Retail deep freeze cabinets: These systems rely on natural convection of cold air with no forced air movement.
The heat transfer rate is low, and hardening can take up to 12 to 24 hours.
- Forced draft hardening room: These rooms utilize high-velocity cold air (blast freezing at $-30^\circ$C to $-40^\circ$C).
The convective heat transfer rate is high, reducing the hardening time to approximately 4 to 8 hours depending on package size.
- Contact Plate hardener: This system places packaged ice cream directly between hollow metal plates containing circulating refrigerant.
Heat is transferred by direct conduction through the metal plates, which is much faster than convection through air.
This direct contact results in extremely rapid heat extraction, hardening the ice cream in less than 0.5 to 1.5 hours.
Therefore, the contact plate hardener achieves the least hardening time.
Step 3: Final Answer
The correct option is (D).
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