Cold storage is the practice of controlling product temperature between −35°C and 15°C to suppress micro-organisms, slow biochemical reactions and extend shelf life. As the temperature falls, enzymes and bacteria lose their ability to act — the scientific basis of the whole industrial cold storage sector.
Food processing uses three main methods: chilling, freezing and IQF fast freezing. Each works in its own temperature band, serves a different group of products and needs purpose-made equipment. This article sets out in detail the temperature standards for each product group, the operating procedure inside a plant, the equipment required, and the common mistakes to avoid. Tan Long, with more than 20 years designing and building industrial refrigeration systems, shares its specialist knowledge in this article.
What is refrigerated storage?
Refrigerated storage (cold storage / refrigeration) is the practice of controlling product temperature between −35°C and 15°C (−31°F to 59°F) to slow biological breakdown. Low temperature suppresses micro-organisms, slows the rate of enzymereactions and limits oxidation, extending the product’s shelf life.
Refrigerated storage is not limited to food. Pharmaceuticals, vaccines, cut flowers and industrial chemicals all need low-temperature storage to hold their quality. "Refrigerated storage" is an umbrella term covering both chilling above freezing and freezing at deep sub-zero temperatures.
So are refrigerated storage and frozen storage the same thing? The two differ in their temperature threshold and in the state of the water inside the product.
Refrigerated storage and frozen storage distinguished
Refrigerated storage holds the product above its freezing point, with the water in the cells still liquid. Frozen storage takes the temperature below −18°C (0°F), turning the water into ice crystals and stopping micro-organisms entirely.
| Criteria | Chilling | Freezing |
|---|---|---|
| Temperature | −1°C to 15°C (30°F to 59°F) | −18°C to −40°C (0°F to −40°F) |
| State of the water in the cells | Liquid | Frozen (ice crystals) |
| Storage time | 3 to 30 days | 3 to 18 months |
| Suitable product | Vegetables, fruit, milk, eggs, cut flowers | Meat, seafood, processed food |
| Typical equipment | Chill rooms, industrial display chillers | Freezer rooms, blast freezing tunnels, freezers |
A business needs to be clear about its storage purpose before choosing a method. Short-term storage of 3 to 7 days for fruit and vegetables needs only a chill room. Frozen seafood held 6 to 18 months for export needs a freezer store at −25°C or below.
How refrigerated storage works
Refrigerated storage works on a thermodynamic principle: as the temperature falls, the molecular energy in the cells falls with it, so biochemical reactions slow down. Below 4°C (39°F), most pathogenic bacteria stop multiplying.
The first mechanism is enzyme suppression. Enzymes catalyse the breakdown of proteins, lipids and carbohydrates in food. Low temperature reduces enzyme activity, delaying rancidity, discolouration and loss of flavour. The second is microbial suppression. Harmful bacteria such as Salmonella, Listeria monocytogenes and E. coli grow best between 20°C and 40°C. Below 4°C their ability to multiply falls sharply. At −18°C, activity stops altogether.
Under FDA guidance, the band from 4°C to 60°C (40°F to 140°F) is called the danger zone. Within it, bacteria double every 20 minutes. So which storage method should each type of product use?
Three common industrial refrigerated storage methods
Food processing uses three main refrigerated storage methods, from the warmest to the coldest: cooling, freezing and IQF fast freezing. Each serves a different group of products and a different storage purpose.
Cooling, 0°C to 15°C
Cooling holds the product at 0°C to 15°C (32°F to 59°F), suiting vegetables, fruit, fresh milk, eggs and cut flowers. Storage life ranges from 3 to 30 days depending on the product. It is the least energy-intensive of the three. Typical equipment: chill rooms, pre-processing chill rooms and industrial display chillers.
Freezing, −18°C to −30°C
Freezing takes the product down to −18°C to −30°C (−0.4°F to −22°F). The water in the cells freezes and micro-organisms stop. This suits meat, seafood and ready-prepared food, with a storage life of 3 to 18 months. Equipment: freezer rooms, blast freezing tunnels and contact freezers.
Note: slow freezing forms large ice crystals that break down the cell structure. The product loses noticeable quality on thawing because bound water is lost.
IQF (individual quick freezing)
IQF fast freezing takes the product core down to −18°C in only 30 to 120 minutes, depending on size. The ice crystals formed are very small (under 100 micrometres) and do not rupture the cell membranes. The product keeps its shape, flavour and nutritional value after thawing. IQF freezes each unit separately: shrimp, fish fillets and cut vegetables do not stick together in a block.
Tân Long has been manufacturing IQF freezing lines since 2011. Tân Long IQF systems run at major seafood plants such as Kyokuyo Vina Foods and Frescol Tuna Vietnam, holding product losses below 2%. So what is the specific temperature for each type of product?
Storage temperature standards by product type
Storage temperature directly determines product quality and shelf life. A deviation of 2 to 3°C from the standard threshold is enough for bacteria to start growing again or for the cell structure to be damaged.
| Product group | Temperature (°C) | Temperature (°F) | Storage time | Method |
|---|---|---|---|---|
| Vegetables (cabbage, carrot, cucumber) | 0 to 5 | 32 to 41 | 7 to 30 days | Cooling |
| Tropical fruit (mango, dragon fruit, durian) | 8 to 12 | 46 to 54 | 14 to 30 days | Cooling |
| Fresh meat (beef, pork, poultry) | 0 to 2 | 32 to 36 | 3 to 5 days | Cooling |
| Frozen meat | −18 to −25 | −0.4 to −13 | 6 to 12 months | Frozen |
| Fresh seafood (shrimp, fish, squid) | -1 to 2 | 30 to 36 | 1 to 3 days | Cooling |
| Frozen seafood | −18 to −35 | −0.4 to −31 | 6 to 18 months | Freezing / IQF |
| Milk, eggs | 0 to 4 | 32 to 39 | 7 to 14 days | Cooling |
| Pharmaceuticals, vaccines | 2 to 8 | 36 to 46 | As specified by the manufacturer | Cooling |
| Cut flowers (roses, chrysanthemums, lilies) | 1 to 10 | 34 to 50 | 5 to 14 days | Cooling |
Tropical fruit (mango, banana, durian) must not go below 10°C. Too low a temperature causes chilling injury, leaving the flesh brown and mushy once it comes out of store. So what is the specific procedure for reaching and holding these temperatures in a plant?
The refrigerated storage procedure in a production plant
The refrigerated storage procedure in a plant has five consecutive stages: product preparation, pre-cooling, transfer into the cold store or freezer, continuous temperature control, and dispatch on a FIFO basis:
- Stage 1, preparation: The product is washed, sorted and any damaged parts removed. It is vacuum packed or shrink-wrapped before chilling to limit contact with air.
- Stage 2, pre-cooling: The product temperature is brought down from ambient to 4 to 10°C (39 to 50°F) over 2 to 4 hours, using a chill room or circulating chilled water. This step lightens the load on the freezing system at the next stage.
- Stage 3, into the cold store or freezer: Depending on the product, the business chooses a chill room (−1 to 5°C) for short-term storage, a freezer room (−18 to −25°C) for long term, or an IQF system for fast freezing of individual pieces.
- Stage 4, continuous temperature control: A PLC or SCADA monitoring system records temperature 24/7. A deviation of more than 1°C triggers an automatic alarm. Tân Long integrates SCADA control panels across its cold stores, holding control to ±0.5°C.
- Stage 5, dispatch: Follow FIFO (first in, first out). Dispatch should take no more than 30 minutes to avoid breaking the cold chain.
One exception to note: produce such as potatoes, onions and garlic needs a curing stage of 10 to 14 days at 18 to 20°C (64 to 68°F) before going into cold storage. Curing hardens the skin and reduces mechanical damage during storage.
Equipment needed for an industrial refrigerated storage system
An industrial refrigerated storage system has five core items: the cold store itself (insulated panels), the compressor, the condenser, the evaporator and the control panel. Choosing the right equipment for the storage requirement keeps running costs down and losses low.
| Storage requirement | Suitable equipment | Operating temperature |
|---|---|---|
| Short-term storage of fruit, vegetables and produce | Cool storage | 0 to 5°C |
| Long-term frozen storage of meat and seafood | Cold storage | -18 to -25°C |
| Fast freezing of seafood, fruit and vegetables | IQF conveyor | −35 to −40°C |
| Batch freezing | Air blast freezing tunnels, contact plate freezers | −35 to −40°C |
| Flake ice production for icing seafood | Flake ice machine | -20°C |
Beyond the main equipment, the system needs a evaporative condenser (heat rejection), pressure vessels (holding refrigerant) and a PLC/SCADA control panel (automation). Tân Long designs and manufactures all of this at its factory in Tây Ninh (formerly Long An), providing a complete solution from consultation and design through installation to maintenance.
With cold storage for produce storage, a IQF conveyor system for a seafood plant, or air blast freezer for batch freezing — Tân Long supplies the right solution at any scale of production.
Having the right equipment is necessary but not sufficient. Operating it incorrectly, or failing to control the temperature, still causes serious losses. Here are the common mistakes and how to avoid them.
Common refrigerated storage mistakes and how to fix them
The three most common mistakes are: leaving product in the 4 to 60°C danger zone too long, mixing raw and cooked product in the same store, and failing to monitor temperature continuously. Each typically costs 15 to 30% of the value of the goods.
A break in the cold chain occurs when product moves between stores without temperature control in between. Stacking too densely blocks the circulation of cold air, creating local hot spots in the store. Skipping the pre-cooling stage and putting warm product straight into the freezer increases the load on the compressor and shortens equipment life.
Does refrigerated storage destroy nutrients in food?
No. Stored at the correct temperature, food keeps its original nutritional value. Meat, poultry and seafood change very little in protein and mineral content after freezing. Poultry bones darkening on thawing is caused by marrow pigment seeping through the porous bone, not by any loss of nutrients.
Industrially frozen fruit and vegetables (IQF) actually keep their vitamins better than "fresh" produce shipped over 3 to 5 days, because freezing locks the nutrients in at the moment of harvest.
What temperature is the "danger zone" for food?
The danger zone is the band from 4°C to 60°C (40°F to 140°F). Within it, bacteria double every 20 minutes. Food left in the danger zone for more than 2 hours has to be discarded. It cannot be "rescued" by refreezing, because freezing only suppresses bacteria, it does not kill them.
When should a business invest in its own cold store rather than renting?
Investing in your own cold store makes sense when throughput is steadily above 500 kg a day (1,100 lbs a day) and the storage cycle repeats year round. Renting suits a seasonal business or one with variable throughput. A cold store investment typically pays back in 2 to 4 years of continuous operation, against rental costs that accumulate year after year.
Tân Long advises free of charge on the cold storage solution that suits your scale of business. Contact our engineers for a site survey.
See also:
- What is quick freezing? The secret to keeping food fresh.
- What is cold storage? The optimal preservation solution in 2026.
- What is a cold supply chain? Structure, operation, and business benefits.
Frequently asked questions about refrigerated storage
What is refrigerated storage?
Refrigerated storage keeps a product at a low temperature but above its freezing point, slowing microbial activity and biochemical reactions and so extending shelf life without freezing the product.
How does refrigerated storage differ from frozen storage?
Refrigerated storage keeps the product fresh and unfrozen, with a storage life measured in days or weeks. Frozen storage takes the temperature below the freezing point, lasting months but changing the product’s structure.
What does the storage temperature depend on?
On the particular product. Fruit and vegetables, meat, seafood, dairy and pharmaceuticals each have their own optimum temperature and humidity range, and the wrong band causes chilling injury or shortens storage life.
Besides temperature, what else affects refrigerated storage?
Relative humidity, air circulation speed within the room, how stable the temperature is, how goods are stacked so air moves evenly, and how clean the store is kept.
Does Tân Long build refrigerated storage facilities?
Yes. Tân Long designs and builds refrigerated storage to the exact temperature and humidity range of each type of goods, from the heat load survey through installation to operational handover.
Related pages
- What is preservation? Common preservation methods today.
- What is VRV cooling system? Advantages, disadvantages and operating principle
- What is Surimi? Origin, classification and how to preserve Surimi
- What is a capacitor? Structure, operating principle and function of capacitors
- What are cold storage materials? Instructions on how to choose cold storage materials
- industrial refrigeration systems designed and built by Tan Long
Is your business in need of a survey, upgrade, or new design for your industrial refrigeration system?
With over 18 years of practical experience leading more than 29 major national projects, Tan Long's team of HVAC engineers is committed to providing accurate thermal load calculations, optimizing the COP efficiency coefficient, switching between natural refrigerants NH3/CO2, and saving 20–30% in operating electricity costs.
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.
