A tunnel freezer is a refrigeration unit used to freeze food quickly and efficiently. It works by passing food through a cold tunnel where it is rapidly frozen using either air or liquid refrigeration methods. It moves products on a conveyor belt through temperature-controlled zones to lock in freshness. This helps preserve food’s quality, texture, and taste.
[Table of contents]
- How does a tunnel freezer work?
- What temperature is a tunnel freezer?
- What is the tunnel freezing method?
How does a tunnel freezer work?
A tunnel freezer uses cold air or a refrigerant¹ system to freeze food as it moves along a conveyor belt rapidly. The food is exposed to low temperatures for a set period, ensuring uniform freezing and preserving its quality.
Food moves on a belt through three stages:
- Pre-cooling (-10°C)
- Deep freezing (-30°C)
- Stabilization (-18°C)
Fans blow cold air from all directions.
The Freezing Process in 3 Steps :
Using chicken nuggets as an example
| Stage | Temperature | Time | What Happens |
| 1 | -5°C | 2 min | Surface hardens |
| 2 | -35°C | 5 min | Core freezes |
| 3 | -20°C | 3 min | Temperature balances |
Why speed matters?
Slow freezing makes ice crystals puncture cell walls. Quick freezing keeps juices inside – that’s why frozen berries still taste fresh.
What temperature is a tunnel freezer?²
Tunnel freezers typically operate at temperatures ranging from -18°C to -40°C (-0.4°F to -40°F), depending on the type of product being frozen. The specific temperature depends on the freezing requirements of the food being processed.
Temperature Customization
See how different foods require specific settings:
| Food Type | Temperature | Time |
| French fries | -35°C | 12 min |
| Shrimp | -40°C | 8 min |
| Dough | -25°C | 20 min |
What is the tunnel freezing method?³
The tunnel freezing method involves placing food on a conveyor that moves through a long tunnel. Cold air or refrigerant circulates the food, freezing it quickly. This method is effective for preserving food’s flavor, nutrients, and texture while minimizing ice crystal formation.
4 Key Design Features
- Spiral nozzles – swirl air like a tornado
- Variable speed belts – adjustable from 0.5-5 m/min
- Zoned insulation – saves 30% of energy
- Automatic defrost – prevents ice buildup
Conclusion:
Tunnel freezers freeze food fast using controlled cold air flow, preserving quality better than traditional methods. Temperature and timing are precisely adjustable.
Footnotes
- Explanation: The refrigerant of tunnel freezers is commonly used in liquid nitrogen (at -196 °Celsius) or carbon dioxide (at -56,6 °Celsius). Click this link to explain the types of refrigerants and cooling methods used in tunnel freezers.↩
- Explanation: The freezing temperature of the tunnel freezer varies based on the product type. Click this link to provide more background information or examples of different industries and their specific freezing temperature requirements.↩
- Explanation: Tunnel freezing method enables food production lines to reduce the temperature of food from 160°F to 0°F in a matter of minutes, preventing the growth of harmful bacteria. Tunnel cooling and freezing can also impact energy efficiency, shelf life, and even cost savings in your commercial food operations. Click here to explain the science behind tunnel freezing in detail.↩
