Tuna Sashimi-grade tuna is a high-end seafood export product from Vietnam, generating nearly $1 billion in export revenue annually to markets such as Japan, the US, and the EU. The specific requirements for sashimi-grade tuna necessitate a cold storage system that maintains a specific temperature. Ultra-low temperature from -50°C to -60°C This aims to completely inhibit the oxidation and denaturation of myoglobin, absolutely preserving the natural ruby red color and the firm, crisp texture of the fish meat. Tan Long As a leading EPC general contractor in Vietnam, we master the design and construction solutions for advanced two-stage refrigeration systems for the preservation chain of ocean tuna.
🏢 Tan Long General Contractor's Practical Implementation Capabilities
Tan Long proudly serves as a general contractor for industrial HVAC systems, undertaking top-tier cold supply chain projects:
- Ca Mau Clean Seafood Processing Complex: Ultra-fast freezing system, -40°C blast freezer, and EU-standard seafood export storage system.
- ASRS NECS automatic cold storage (Long An): 102,642 pallet positions with a temperature range of -20°C to -25°C.
- AJ Total Vietnam (Long Hau & Pho Noi Industrial Parks): 31,000 pallet positions, Mycom & Freon inverter NH3 screw compressors.
1. Why is it necessary to store tuna in ultra-cold storage at -50°C to -60°C?
For most types of seafood, freezing temperatures between -18°C and -25°C are sufficient to prevent microbial growth. However, for tuna intended for raw consumption (Sashimi/Sushi), the technical standards are completely different:
- Anti-myoglobin pigmentation disorders: Myoglobin in tuna muscle tissue is extremely sensitive to oxygen. At temperatures between -18°C and -20°C, myoglobin is still oxidized to metmyoglobin, causing the fish meat to turn dark brown and lose its premium commercial value. Only when the temperature drops below -50°C is this reaction completely neutralized, preserving the bright red color of the meat as if it were freshly caught.
- Completely inhibit the activity of the enzyme that breaks down substances: The breakdown of proteins and unsaturated fats (Omega-3) remains intact throughout the storage period of 12-24 months.
- Preventing ice crystals from breaking down the structure of cellular tissue: Rapid deep freezing helps form ultrafine ice crystals, and when thawed, it does not cause loss of moisture (drip loss). (< 2%), the fish meat retains its mechanical elasticity.
2. Technical Standards for Tan Long's Ultra-High-Speed Refrigeration System
| Technical Item | Ultra-Cold Freezing Chamber for Tuna | Ultra-Cold Freezer Storage (-50°C to -60°C) |
|---|---|---|
| Operating temperature range | -55°C to -65°C | -50°C to -55°C (continuously stable) |
| Insulated shell structure | PIR panel with a density of 45-48 kg/m³, 200mm thick, and double-sided 304 stainless steel. | PIR panels with a density of 42-45 kg/m³, a thickness of 175-200mm, and camlock fastening. |
| Compressor system | Two-stage or Cascade compressor unit (CO2/NH3 or R23/R404A) | Bitzer / Mycom / Kobelco 2-stage screw auger specifically designed for ultra-low temperatures. |
| Evaporator & Defrosting | Large fin pitch (10-12mm) evaporator, extreme frost prevention, hot gas defrosting. | Ceiling-mounted indoor unit with aluminum fins and stainless/copper tubing, high-pressure fan. |
| Underfloor heating system | Multi-stage underfloor heating resistors + forced ventilation to prevent frost buildup. | Cooling oil circulation tube or double heater cable 100% spare |
3. Standard EPC Cold Chain Operation Procedure for Exporting Tuna
- Pre-processing & Sorting at the Port: Upon arrival at the port, the tuna are immediately transferred to the ante-room at a temperature of 5°C – 8°C for bleeding, gutting, cleaning, and vacuum packaging.
- Ultra-fast freezing in a freezer (-60°C): Using a high-speed, multi-directional air blast freezer with a speed of 4–6 m/s, the core temperature of the fish is brought to -50°C within 8–10 hours.
- Transferring commercial cold storage: Stack on pallets or specialized shelves in a -55°C warehouse, and manage shipments by batch using an RFID barcode system.
- Loading and unloading export containers: Using an automated dock leveler combined with an air cushion dock shelter prevents heat loss to the external environment.
4. Cost Estimate Table for the Construction of a Tuna Cold Storage Facility
The investment cost for a cold storage facility depends on the freezing capacity per batch and the storage volume. Below is a table showing the estimated technical cost breakdown:
| Expense Category | Technical Specifications Meet Standards | Percentage in Total Investment |
|---|---|---|
| Two-stage ultra-refrigeration compressor unit | Imported from Bitzer (Germany) / Mycom (Japan), Inverter, water-cooled. | 40% – 45% |
| Insulated casing & Frost-free door | 200mm PIR panel, fire-resistant B1, 304 stainless steel, 4-sided electric sliding door with heating. | 25% – 30% |
| Cooling unit & piping system | High-pressure cold-resistant steel pipe, insulated with Armaflex/Aeroflex coating, 50mm | 15% – 18% |
| PLC SCADA and Sensor Control Panels | HMI touchscreen display, IoT monitoring with SMS/App alerts 24/7. | 8% – 12% |
5. Tan Long General Contractor's Commitment to Capacity
- Conduct a site survey and calculate the thermal load according to ASHRAE standards, accurately down to the kW level.
- Genuine 100% compressor, pressure vessel, and expansion valve equipment, complete with CO, CQ, and pressure safety inspection certificates.
- We offer turnkey construction (EPC) services, including support for acceptance testing, inspection, and safe operation training.
- Comprehensive 24-month warranty, 24/7 technical support service within 2 hours in key coastal areas (Binh Dinh, Phu Yen, Nha Trang, Vung Tau, Kien Giang…).
Is your business in need of constructing a seafood freezing warehouse or IQF conveyor belt system?
Tan Long provides complete industrial refrigeration solutions: blast freezers, ultra-low temperature freezers from -25°C to -60°C (Japanese Sashimi standard), and ultra-fast IQF conveyor systems, preserving cell tissue structure and meeting export standards such as HACCP, EU Code, and US FDA.
Engineer Nguyen Toan Thinh (Technical Director)
With over 18 years of practical experience in directing, consulting, designing, and constructing heavy industrial refrigeration systems, ASRS automated warehouses, and IQF freezing systems across more than 29 major national projects.
