Introduction to Specialized Cold Storage for Seafood Storage

Fish have high water content and fragile muscle fibers, making them extremely prone to spoilage. Additionally, different fish have significant differences in their freezing points, so freezing and storage must accurately control temperature based on their characteristics. This prevents damage to the fish meat, preserves nutritional components, and avoids dry, stringy texture and water loss after thawing.

•  Common Marine Fish (Hairtail, Croaker, Spanish Mackerel, etc.)

The optimal freezing temperature ranges from -18℃ to -20℃, with a stable storage temperature of -18℃±1℃, allowing for storage periods of 3-6 months. Before warehousing, quick freezing treatment is required to lower the core temperature of the fish meat to below -18℃ within 2 hours—this locks in the fish’s moisture and nutrients, preventing ice crystal formation from damaging muscle fibers. Sealed fresh-keeping bags or vacuum packaging are used to prevent odor mixing and water loss, while the air flow rate in the warehouse is controlled at 0.2-0.3m/s to avoid thawing and refreezing caused by local temperature fluctuations.

•  High-End Marine Fish (Salmon, Cod, Tuna, etc.)

These fish have extremely high temperature requirements, with an optimal freezing temperature of -25℃ to -30℃ and a storage temperature fluctuation of no more than ±0.5℃, enabling storage for 6-12 months. Ultra-low temperature quick freezing technology (liquid nitrogen freezing or air-cooled quick freezing) is required to reduce the core temperature of the fish meat to -30℃ within 1 hour, maximizing the retention of its fresh, tender taste and unsaturated fatty acids. During storage, frequent opening and closing of the cold storage door should be avoided to prevent temperature fluctuations; independent sealed packaging is used to prevent odor mixing, and the condition of the fish meat should be checked regularly to promptly remove any spoiled individuals.

•  Freshwater Fish (Carp, Grass Carp, Crucian Carp, etc.)

The suitable freezing temperature is -15℃ to -18℃, which can be stored for 2-4 months. Freshwater fish have a strong fishy smell and need to be stored in separate partitions. Before warehousing, the internal organs should be removed and cleaned, and sealed packaging should be used. The warehouse should be equipped with a deodorizing device to regularly ventilate and exhaust odors and carbon dioxide, avoiding the fish meat from absorbing odors. At the same time, the humidity in the warehouse is controlled at 60%-70% to prevent frost accumulation.

Shrimp have tender meat, high water content, and thin shells, making them highly susceptible to thawing and spoilage due to temperature fluctuations. They are also prone to black heads and shelling, so the core of their storage lies in "quick freezing, constant temperature freshness locking, and anti-oxidation".

•  Fresh Frozen Shrimp (Prawns, Chinese Shrimp, etc.)

The optimal freezing temperature is -20℃ to -22℃, with a stable storage temperature of -20℃±1℃, allowing for storage periods of 4-8 months. Before warehousing, the shrimp need to be cleaned and graded, and individual quick freezing technology (freezing each shrimp separately) is adopted to avoid adhesion. After freezing, vacuum packaging is used to prevent oxidation and water loss, as well as black heads and shelling. The warehouse is equipped with anti-frost devices to regularly remove frost, preventing frost accumulation from affecting refrigeration efficiency and avoiding frostbite on the shrimp.

•  Crayfish (Fresh Frozen, Cooked Frozen)

The suitable temperature for fresh frozen crayfish is -18℃ to -20℃, which can be stored for 3-6 months; the suitable temperature for cooked frozen crayfish is -15℃ to -18℃, which can be stored for 2-3 months. Fresh crayfish need to be cleaned and the shrimp intestines removed before warehousing. Cooked crayfish need to be cooled to room temperature before warehousing to avoid temperature fluctuations in the warehouse. Both are packaged in sealed packaging and stored in separate partitions to prevent odor mixing. The humidity in the warehouse is controlled at 65%-75% to avoid dryness and shelling of the shrimp.

Most shellfish are shelled seafood, and their shells provide a certain degree of protection. However, their internal meat is tender and high in water content, making them prone to death and spoilage due to oxygen deficiency and temperature fluctuations. Thus, the core of shellfish storage is "low-temperature freshness preservation, appropriate ventilation, and anti-oxygen deficiency".

•  Fresh Shellfish (Scallops, Oysters, Clams, etc.)

The suitable storage temperature is 0℃ to 2℃, with humidity controlled at 90%-95%, allowing for short-term turnover of 3-7 days. A wet-keeping preservation mode is adopted, with regular water changes to ensure adequate oxygen supply for the shellfish and prevent death from oxygen deficiency. They are stored in separate partitions to avoid shell damage caused by extrusion, and the air flow rate in the warehouse is controlled at 0.1-0.2m/s to prevent dehydration and death of the shellfish from direct cold air blowing.

•  Frozen Shellfish (Shelled Meat, Frozen Shelled Shellfish)

The suitable freezing temperature is -18℃ to -20℃, which can be stored for 6-8 months. Shelled meat needs to be quickly frozen to a core temperature below -18℃ and packaged in vacuum to prevent oxidation and water loss. Frozen shelled shellfish need to be cleaned and drained before freezing to avoid adhesion due to shell freezing. The temperature in the warehouse is stable at -18℃±1℃ to avoid spoilage and poor taste of the shellfish meat caused by thawing and refreezing.

Crustacean seafood (crabs, lobsters) have plump meat and are rich in protein. In their fresh state, they have extremely high requirements for temperature and humidity; after freezing, they are prone to dry, stringy meat and loss of crab roe or shrimp roe. Therefore, the core of crustacean storage is "precise temperature control, moisture retention and freshness locking, and anti-extrusion".

•  Fresh Crustaceans (Hairy Crabs, Swimming Crabs, Lobsters, etc.)

The suitable storage temperature is 0℃ to 1℃, with humidity controlled at 90%-95%, allowing for short-term turnover of 1-3 days. They are stored in layers to avoid limb damage and loss of crab roe or shrimp roe caused by extrusion. Water is sprayed regularly to keep them moist, adequate ventilation is ensured to prevent death from oxygen deficiency, and they are stored in separate partitions to avoid odor mixing. The temperature fluctuation in the warehouse does not exceed ±0.5℃ to prevent frostbite or spoilage due to high temperatures.

•  Frozen Crustaceans (Frozen Crabs, Frozen Lobsters)

The suitable freezing temperature is -20℃ to -25℃, which can be stored for 4-6 months. Before freezing, they need to be cleaned and tied to avoid limb loss after freezing. Quick freezing technology is adopted to reduce the core temperature to below -20℃ within 2 hours, locking the water and nutrition of the meat. Vacuum packaging is used and stored in separate partitions to avoid odor mixing and extrusion. The warehouse is regularly defrosted to prevent frost accumulation from affecting the refrigeration effect.

•  Fresh-Keeping Cold Storage (0℃ to 2℃)

Suitable for short-term turnover seafood such as fresh shellfish and fresh crustaceans, this type of cold storage uses insulation panels with a thickness of 150mm. This thickness effectively blocks external heat penetration, maintains a constant temperature and humidity environment in the warehouse, and balances energy efficiency and economy. If the region is hot in summer (outdoor maximum temperature ≥35℃) or has high humidity (annual average humidity ≥75%), the thickness can be slightly adjusted to 180mm to enhance thermal insulation and moisture-proof effects, reduce the operational load of refrigeration and dehumidification equipment, and prevent condensation and frost in the warehouse. Additionally, the warehouse is equipped with a gentle air circulation system to avoid uneven local temperature and humidity, which could lead to the death of fresh seafood.

•  Conventional Freezing Cold Storage (-15℃ to -20℃)

Suitable for common marine fish, freshwater fish, frozen shrimp, frozen shellfish, and other seafood, this cold storage uses 200mm-thick insulation panels— the conventional standard thickness for seafood cold storage. This thickness ensures that the temperature fluctuation in the warehouse does not exceed ±1℃, effectively reducing energy consumption while balancing insulation effectiveness and construction costs, making it the most widely used thickness specification in the seafood industry. The joints of the panels are sealed and thermally broken, with gaps filled with sealant to reduce cold bridge loss and moisture penetration, preventing frost in the warehouse. At the same time, air-cooled evaporators are installed to improve refrigeration uniformity and avoid local thawing.

•  Ultra-Low Temperature Freezing Cold Storage (-25℃ to -30℃)

Designed for high-end marine fish, frozen crustaceans, and other seafood with extremely high temperature requirements, this cold storage uses 250mm-thick insulation panels (which can be upgraded to 300mm for long-term storage below -30℃). This type of cold storage requires a stable ultra-low temperature environment, and thicker panels effectively block external heat penetration, avoid cold air loss, and reduce the operational load of refrigeration units, thereby lowering energy consumption. The panels must pass a -40℃ low-temperature shrinkage test with a deformation rate ≤0.5% to ensure stability in ultra-low temperature environments. The warehouse is also equipped with efficient frost-proof and defrosting equipment (such as electric defrosters) combined with an AI defrosting system to prevent frost accumulation from affecting refrigeration efficiency, while controlling temperature fluctuations during defrosting to ≤1℃.

•  Selection of outer panel material

This is adjusted based on the usage scenario. 304 stainless steel plates (0.6-1.0mm thick) are preferred, as they offer corrosion resistance, easy cleaning, and odorlessness—making them suitable for the humid, fishy environment of seafood cold storage and compliant with food hygiene requirements. For coastal or high-salt fog areas, 316L stainless steel plates (0.8-1.2mm thick) are recommended, as they provide stronger corrosion and salt fog resistance to prevent panel moisture and rust. For ordinary freezing cold storage, color steel plates (0.4-0.6mm thick) can be used, offering rust prevention, decoration, and economy; however, moisture-proof and anti-corrosion treatment (such as applying anti-corrosion coating) is required to avoid panel erosion by seafood water vapor.

•  Regional adjustment principle

In cold northern regions (where outdoor temperatures drop below -20℃ in winter), the thickness of insulation panels for cold storage in the same temperature range can be increased by 30mm-50mm to enhance thermal insulation and reduce energy consumption. Cold-proof curtains are also installed to minimize cold air loss when the cold storage door is opened. In hot, high-humidity southern regions (outdoor maximum temperature ≥35℃, annual average humidity ≥75%), the panel thickness can be slightly increased by 20mm-30mm, and efficient dehumidification and frost-proof equipment are added to balance thermal insulation, moisture resistance, and cost—preventing panel damage caused by condensation in the warehouse. For large-scale seafood cold storage (storage capacity ≥1000㎡), due to the higher risk of cold air loss, it is recommended to increase the panel thickness by 30mm based on the corresponding standard thickness, while optimizing the layout of refrigeration units to improve refrigeration uniformity and ensure a stable ultra-low temperature environment in the warehouse.

•  Insulation and frost prevention details

The cold storage door must be equipped with airtight strips, automatic door-closing devices, and observation windows, matched to the thickness of the insulation panels and fitted with cold-proof insulation layers to prevent cold air loss and external moisture entry. Cold bridge areas must be thermally broken and equipped with cold bridge blockers to prevent condensation and frost in the warehouse. The ground must be equipped with a ventilated elevated layer or electric tracing system to prevent foundation frost heave and facilitate cleaning and disinfection. Additionally, the ground of the seafood cold storage must undergo anti-corrosion and anti-leakage treatment (such as laying an epoxy resin floor) to avoid erosion by seafood blood. The walls and ground inside the warehouse must be smooth, flat, and free of cracks to facilitate cleaning and deodorization, reducing mold growth. The warehouse is also equipped with frost-proof fans and defrosting systems to regularly remove frost and ensure refrigeration efficiency, while the sealing performance of the panels is checked regularly to promptly repair any damaged areas.