Nov 13, 2025
In the food freezing and cold-chain industry, liquid nitrogen tunnel freezers are widely used because of their extremely low temperatures and fast freezing ability. Many customers want to know: How cold can a liquid nitrogen tunnel freezer get? And how do different temperatures affect food quality, energy use, safety, and production?
This article explains the basics of liquid nitrogen, the temperature range inside the tunnel, how temperature is measured, how different temperatures affect food, safety requirements, and how liquid nitrogen systems compare with traditional mechanical freezers. This helps production managers, engineers, and buyers make the right decision when choosing equipment.
Liquid nitrogen (LN?) has a boiling point of –196°C at normal pressure.This means that in theory it can create an environment close to −196°C.
However, the inside of a tunnel freezer is not filled entirely with liquid nitrogen. In real systems, freezing is achieved in several ways:
● Liquid nitrogen spray / mist: LN? is sprayed as fine drops to create strong heat transfer.
● Cold nitrogen gas: Frozen gas after evaporation cools the food without direct liquid contact.
● Mixed method: First harden the surface quickly, then cool the inside with cold airflow.
So even though liquid nitrogen itself is −196°C, the temperature inside the tunnel and on the food depends on design, airflow, belt speed, and product load.
In real operation, three types of temperature are important:
① Surface temperature
Affects icing, crust formation, and product appearance.
② Core temperature
Measured by a probe inside the food.This temperature relates to food safety and proper freezing.
③ Airflow temperature inside the tunnel
This is the temperature of the cold gas blowing across the food.
Key measurement rules:
● Use multiple sensors in different positions.
● Record temperatures in real time so each batch can be traced.
● Measure the time for food to pass through −1°C to −5°C, the “ice crystal zone.”
● Use sensors suitable for very low temperatures (like K-type or T-type thermocouples).
Typical real temperatures
● Food surface may drop to −60°C to −100°C within seconds.
● Core temperature may take several minutes to reach −18°C, depending on thickness.
Understanding temperature effects is key to good freezing performance.
① Extremely cold surface (below −60°C)
Benefits:
● Very fast crust freezing
● Food keeps shape, color, and does not stick together
Possible risks:
● Coated or sugary products may crack
● Surface may be damaged if cooling is too strong
Solution:Reduce spray strength, increase gas-phase cooling.
② The “ice crystal zone” (−1°C to −5°C)
This is the most important zone.Ice crystals grow fastest here.
● The faster food passes this zone,
● The smaller the ice crystals,
● The better the texture and juice retention after thawing.
Liquid nitrogen tunnels are designed to pass through this zone as fast as possible.
③ −18°C and below (standard freezer temperature)
Most frozen foods are stored long-term at −18°C.Products with more fat (like salmon or beef steak) often store better at −25°C or −30°C.
④ Ultra-low temperatures (−80°C and lower)
Used mostly in research, special seafood, or high-value tests.Not common for commercial freezing because the cost is high and special materials are required.
Liquid nitrogen freezing involves very low temperatures and a large amount of nitrogen gas. Important safety points include:
Main risks:
● Low oxygen (asphyxiation): Nitrogen gas can reduce oxygen concentration.→ Install oxygen alarms and strong ventilation.
● Cold burns: Workers must wear gloves, face shields, and protective clothing.
● Material brittleness: Some plastics and rubber break at low temperatures.→ Equipment must use low-temperature-safe materials.
● Pressure safety: LN? tanks and pipelines need safety valves and isolation valves.
● Food safety documents: Keep temperature records, alarm logs, and cleaning records.
| Item | Liquid Nitrogen Tunnel | Mechanical Freezers (Freon/CO?/Ammonia) |
| Lowest temperature | Close to −196°C | Usually −40°C (special design −60°C) |
| Freezing speed | Very fast | Slower |
| Energy/Running cost | LN? consumption cost | Lower long-term electricity cost |
| Best for | High-value IQF foods, fast crust freezing | Large cold rooms, mass storage |
| Response to load | Instant cooling | Slower response |
? Misunderstanding 1: “Lower temperature is always better”
Extreme surface temperature may waste LN? and damage food.The goal should be the best freezing curve, not the lowest number.
? Misunderstanding 2: “More liquid nitrogen gives better quality”
Excess LN? without proper design = waste + uneven freezing.Correct method: fine spray control, zone control, and proper belt speed.
Practical tips:
● Check spray nozzles, insulation, and valves regularly.
● Monitor LN? usage per kg of product (L/kg).
● Record data daily to detect abnormal consumption early.
Liquid nitrogen tunnel freezers can theoretically reach −196°C, but the important point is not the extreme temperature. Instead, focus on:
● The freezing curve
● The speed through the ice crystal zone
● The time needed to cool the product core
● Matching temperature zones to each food type
● Safety systems and measurement systems
● Combining LN? freezing with mechanical cold rooms
When designed well, liquid nitrogen tunnels give the best food quality, faster freezing, and stronger market value.
SPEEDCRYO specializes in liquid nitrogen freezing systems, IQF tunnel freezers, and complete engineering services. We provide:
● Product testing
● Freezing curve development
● Cleaning and hygiene plans
● On-site setup and training
● Customized design for different food types
If you need product testing or want help selecting the right tunnel freezer, please prepare product samples, target capacity, and a layout drawing. Our engineering team will offer a tailored plan and project budget.
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