Gradual Fish Freezing Using Sub-Chilling to Prevent Surface Damage
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Solution Overview
Problem
Current methods for cooling and freezing fish, such as using ice or vertical freezers, damage the product, create environmental issues, and are inefficient, leading to reduced quality and increased costs.
Innovation Solution
A method involving sub-chilling fish in a salt-controlled and temperature-controlled solution with agitation, followed by temperature balancing to ensure even cooling and prevent surface crust formation, before freezing, using spiral pumps and cooling tanks to achieve a gradual freezing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If fish are frozen directly using vertical plate freezers, then freezing speed is improved, but the food items at the bottom of the receptacle are damaged due to increased load
Solution Approach 1:
The fish are pre-cooled in a cooling chamber before being placed in the freezing chamber. This preliminary cooling action reduces the temperature gradient during freezing, preventing thermal shock and structural damage to the fish while maintaining efficient freezing speed.
2Productivity
If vertical plate freezers are used for freezing, then freezing capacity is improved, but de-riming and defrosting become very time and energy consuming
Solution Approach 1:
The freezing system is divided into multiple independent freezing plates that can be individually controlled. This segmentation allows different zones to be frozen at different rates and stages, enabling selective defrosting of only the necessary sections rather than requiring complete system defrosting, thereby reducing time and energy consumption.
3Productivity
If slurry ice is used to chill fish to an undercooled state, then cooling efficiency is improved, but the surface of the fish freezes and forms an ice shell
Solution Approach 1:
The cooling system continuously circulates the slurry ice through the fish batches, maintaining constant thermal contact and preventing localized overheating that would cause surface freezing. The continuous movement ensures uniform heat distribution and prevents ice shell formation while maintaining high cooling efficiency.
4Reliability
If ice is used for transporting and storing fish, then fish quality is maintained, but the ice damages the fish surface and creates environmental issues
Solution Approach 1:
The system uses a hydraulic slurry ice circulation system instead of solid ice contact. The slurry ice acts as a fluid cooling medium that can be pumped and circulated through the fish, providing uniform cooling without the mechanical damage caused by solid ice contact, while also reducing environmental impact through controlled circulation and reduced waste.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method maintains better quality of fish during cooling, freezing, and storage, reduces energy consumption, and facilitates easier thawing with reduced environmental impact and cost.
Implementation Method 1
bringing the food items to an undercooled state in salt-controlled and temperature-controlled liquid
Implementation Method 2
providing substantially continuous movement of the food items in the solution during the step of bringing the food items to an undercooled state
Implementation Method 3
transferred to receptacle for freezing
Data Source
AI summary
Method and device for freezing food items in a gradual process, where the food items are first put through under-cooling before the food items are placed in a container or receptacle for freezing. The method and device are particularly suitable for freezing freshly slaughtered and bled fish for later processing.