One of the questions we hear most often from food businesses is this: "We already have a -20 °C cold room, do we also need a blast freezer?" The short answer is yes, because the two units are designed for different jobs.
What is the difference between a blast freezer and a cold room?
A blast freezer is used to freeze product, while a cold room is used to store frozen or chilled product. Although they may seem to operate in the same temperature range, their cooling capacities, air velocities and design calculations are completely different.
What is a blast freezer?
A blast freezer is a refrigeration unit that brings product temperature below freezing point in a short time using very low air temperature and high air velocity. The air temperature inside the cabinet is usually between -30 °C and -40 °C, and powerful fans move air quickly through the products.
The goal is to bring the product's core temperature to -18 °C as quickly as possible. There are cabinet, room, tunnel and spiral types; the choice depends on batch size and whether production is continuous.
What is a cold room?
A cold room is an insulated storage space used to keep chilled or frozen product at a set temperature for a long time. Sub-zero storage rooms usually operate between -18 °C and -25 °C.
The refrigeration unit of a cold room is selected to handle heat entering through the walls, door openings and a limited amount of incoming product. The capacity and air velocity needed to freeze large amounts of hot product are usually not part of this calculation. We explained the selection criteria in detail in our cold room installation article.
Comparison table
The main difference between the two units is that one is designed to change the product's temperature and the other to maintain it. This difference shows up in temperature, air velocity and capacity.
| Feature | Blast freezer | Sub-zero cold room |
|---|---|---|
| Function | Freezing product quickly | Storing frozen product |
| Air temperature | Usually -30 / -40 °C | Usually -18 / -25 °C |
| Air velocity | High, directed through the product | Low, focused on even distribution |
| Capacity calculation | Product load is the deciding factor | Wall and door load are the deciding factors |
| Operating mode | Batch (cycle) or continuous line | Continuous storage |
Why does fast freezing affect product quality?
Fast freezing forms small ice crystals inside the product, so it damages the cell structure less. Slow freezing forms large crystals that damage the cell walls.
The result of this difference shows up during thawing: meat, fish or pastry that was frozen slowly loses more water, its texture softens and its flavor declines. Fast freezing also shortens the time the product spends in the temperature range where bacteria grow, which matters for food safety.
In the commonly accepted practice for cooked products, the target is to bring the product from +70 °C to -18 °C at the core in about 4 hours. For blast chilling (cooling without freezing), the target is usually about 90 minutes from +70 °C to +3 °C. Exact times are set according to the business's food safety plan and the product.
Why is putting hot product in a cold room a problem?
Putting hot or freshly cooked product straight into a storage room exceeds the room's cooling capacity and warms the other products inside. The unit runs for hours without stopping, but the room temperature rises.
- Products that were frozen earlier partially thaw and refreeze, and quality drops.
- Moisture from the hot product quickly freezes on the evaporator, and defrost cycles become more frequent.
- The core of the new product stays unfrozen for hours.
- The compressor runs under high load for a long time, increasing energy consumption and the risk of breakdown.
First freeze the product in a blast freezer until its core temperature reaches -18 °C, then move it into the storage room. Use a probe-type thermometer to check the core temperature.
Blast freezer or cold room?
Based on your product and production information, let's determine the right capacity together during the site survey.
What types of blast freezers are there?
Blast freezers are made in different types depending on how the product is loaded and whether production is batch or continuous. The right type is chosen according to the business's daily production volume and workflow.
01Cabinet type
These are compact units used in restaurants, pastry shops and small production kitchens, loaded with trays or GN pans. Capacity per batch is limited, but installation is easy.
02Room type
These are panel-walled blast freezing rooms where product is brought in on trolleys or pallets. They are common in mid-sized facilities producing meat, pastry and ready meals. The panels are thicker than in a storage room, and the evaporator capacity and fan power are significantly higher.
03Tunnel and spiral type
These are systems in which the product freezes while passing continuously on a conveyor. They are used in facilities with high-volume, continuous production. They are designed according to the product's residence time in the tunnel and the line speed.
What should be considered for capacity and maintenance?
A blast freezer's capacity is defined by how many kilograms of product per batch or per hour can be brought from which entry temperature to which core temperature, and in how long. Product thickness and packaging directly affect the time: thick, tightly packaged product takes much longer to freeze than thin, unpackaged product.
Because the unit is exposed to heavy frost, regular checks of the defrost system, evaporator fans and door heaters are essential. Keeping the condenser clean prevents cycle times from getting longer in summer. Leaving air gaps between trays is also a simple but effective rule that shortens freezing time.
The probe record showing core temperature at the end of a cycle is the best indicator of both product quality and unit performance. If the cycle time for the same product keeps getting longer over weeks, it may be a sign of a dirty condenser, low refrigerant, an iced-up evaporator or a tiring compressor. In that case, instead of changing settings, have a qualified technician take measurements.
Which one do you need?
If you produce and freeze your own product, you need a blast freezer; if you buy ready-frozen product and store it, you need a sub-zero cold room. Most businesses that produce food use both together.
When selecting a blast freezer, the amount of product per batch, the product's entry temperature, the packaging type and the target time are the deciding factors. At YOİ Mühendislik, in blast freezer and cold room projects we collect this information during the site survey and present the capacity calculation in writing; the price is determined during the survey. For details, see our cold room service page.
Frequently asked questions
What temperature does a blast freezer run at?
The air temperature inside a blast freezer cabinet is usually between -30 °C and -40 °C. The goal is to bring the product's core temperature down to -18 °C in a short time.
Can a cold room be used instead of a blast freezer?
A storage cold room is not designed to quickly freeze large amounts of hot product. If used that way, the product freezes slowly and the other products in the room warm up.
How does blast freezing affect product quality?
Fast freezing forms small ice crystals and damages the cell structure less. When the product is thawed it loses less water, and its texture and flavor are better preserved.
Is a blast chiller the same as a blast freezer?
No. A blast chiller quickly brings the product down to around +3 °C without freezing it, while a blast freezer lowers the core temperature to -18 °C. Some units can work in both modes.