Why Do Frozen Foods Stick Together? How Tunnel Freezers Solve the Problem

In frozen food processing and storage, product sticking (clumping or adhesion) is a common issue that significantly affects product quality. Items such as dumplings, fish pieces, shrimp, and frozen vegetables often freeze into a single mass, which not only damages appearance but also reduces taste quality, increases sorting loss, and may even harm brand reputation.

So why do frozen foods stick together? And how can advanced freezing technology effectively solve this problem? This article explains the main causes of product adhesion and introduces how tunnel freezers provide an efficient solution.

1. Three Main Causes of Frozen Food Sticking

1) Moisture turns into “ice bridges”

Frozen foods contain a large amount of free water. During slow freezing, water gradually forms ice crystals and migrates to the product surface. When products touch each other, surface moisture freezes and forms thin ice layers—creating “ice bridges” that bind products together.

2) Temperature fluctuations cause ice recrystallization

Unstable freezing temperatures (such as frequent door opening or insufficient cooling capacity) cause partial melting and re-freezing of ice crystals. This repeated process leads to recrystallization, increasing surface adhesion and product clumping.

3) Improper stacking and packaging

• Overlapping or stacked storage increases contact area

• Poor sealing allows moisture exchange and ice formation

• Inadequate pre-cooling leaves internal moisture active, leading to post-freezing adhesion

2. Limitations of Traditional Freezing Methods

Conventional freezers or cold storage systems freeze food slowly (often taking several hours to reach -18°C at the core), which leads to:

Issue	Result
Slow freezing speed	Large ice crystals and moisture migration
Temperature fluctuation	Ice recrystallization and increased sticking
No individual quick freezing	Products freeze into blocks
Manual handling	Low efficiency and higher labor cost

Therefore, traditional freezing methods cannot meet modern food industry requirements for high-quality, fast, and individual quick freezing.

3. Tunnel Freezer: The Key Technology to Solve Sticking Problems

A tunnel freezer is a continuous, high-efficiency freezing system. Food is conveyed through a tunnel via a mesh belt and rapidly frozen in a -35°C to -40°C high-velocity cold air environment. The core temperature of products can quickly drop to -18°C.

How Tunnel Freezers Prevent Product Sticking

✔ Rapid freezing

Products pass quickly through the maximum ice crystal formation zone, reducing moisture migration and preventing surface ice accumulation, effectively avoiding adhesion.

✔ Fluidized IQF tunnel freezing (for granular products)

Through airflow and mechanical vibration, small particles such as shrimp or vegetables are kept in a semi-suspended or fully fluidized state, enabling true Individual Quick Freezing (IQF) and preventing clumping.

✔ Stable temperature control

The enclosed tunnel structure ensures consistent low temperature, preventing ice recrystallization caused by temperature fluctuations.

✔ Single-layer conveying system

Products are evenly distributed on the conveyor belt, minimizing contact and ensuring uniform freezing for each piece.

Note: Sure International’s IQF tunnel freezer is specially designed for products such as vegetables, shrimp, and dumplings, achieving true individual quick freezing. Capacities available include 300kg/h, 500kg/h, and more, effectively solving sticking issues.

4. Tunnel Freezer vs Traditional Freezing Methods

Feature	Traditional Freezing	Tunnel Freezer
Freezing time	2–6 hours	Minutes (continuous)
Ice crystal size	Large, uneven	Fine, uniform
Product sticking risk	High	Very low (IQF type almost zero)
Product quality	Deformation possible	Better shape retention
Production mode	Batch processing	Continuous processing
Automation level	Low	High
Energy efficiency	Low	High

5. Suitable Food Types

Tunnel freezers are widely used for products prone to sticking:

• Dough products: dumplings, buns, spring rolls, baozi

• Seafood: shrimp, fish cubes, fish balls

• Meat products: meatballs, chicken nuggets, beef steaks

• Fruits & vegetables: strawberries, corn kernels, green beans, mixed vegetables

• Others: pizza, fried rice, prepared meals

6. How to Choose the Right Tunnel Freezer

• Capacity selection: Choose based on daily output requirements (100kg/h – 1500kg/h options available)

• IQF requirement: For granular products like peas, blueberries, shrimp, etc., fluidized IQF tunnel freezer is recommended

• Temperature range: Typically around -35°C, with core temperature reaching -18°C

• Conveyor belt material: Stainless steel mesh belt for durability and hygiene

• Energy efficiency: Prefer energy-saving and low-noise designs

7. Conclusion: Freezing Technology Defines Food Quality

Food sticking is not an unavoidable problem—it is the result of inadequate freezing processes. With advantages such as rapid freezing, stable temperature control, and true individual quick freezing, tunnel freezers have become essential equipment in modern food processing.

For food manufacturers aiming for higher product quality, efficiency, and brand competitiveness, investing in a tunnel freezer is not just an equipment upgrade—it is a strategic production improvement.

If you are facing issues such as product sticking, low capacity, or quality loss, contact a professional freezing equipment supplier like Sure International for customized tunnel freezing solutions and achieve true “individual quick freezing with premium product quality.”