Quick freezing generally refers to reducing the temperature of food below its freezing point in the shortest possible time, thereby minimizing water loss and preserving the nutrition and texture of the product.

When food is frozen through fast freezing, there isn’t enough time for water molecules to form large crystals. In contrast, during the slow freezing process, large ice crystals can form, leading to cell damage when the frozen product is thawed.

As the test results have shown, the faster the product’s temperature drops below the freezing point (0℃), the better the freshness of the product will be.

In general, fast freezing should be carried out in an environment ranging from -35℃ to -18°C, and the food should be frozen to -18 ℃ in about 30 minutes. The core temperature of the food should be -18°C to -15°C.

The picture below illustrates how ice crystals form during the freezing process. From the picture, it can be seen that in the slow freezing process, the ice crystals are large, while in fast freezing, the ice crystals are small and evenly sized.

Blast freezing, also known as individual freezing, is the most popular fast freezing method for small and medium-sized products. Depending on the conveyor system and airflow pattern of the blast freezer, it can be further categorized into the spiral freezer, tunnel freezer, and impingement freezer.

The IQF freezer can freeze individual products in a few minutes, typically less than 50 minutes.

Benefits of the IQF Freezer

1. Reduced product water loss: The product can be quickly frozen from ambient temperature to -18°C. For example, chicken nuggets can be frozen from 40°C to -18°C in around 40 minutes. If packed chicken nuggets are placed in cold storage, it would take a day. The shorter freezing time reduces the water loss of the product.

2. Limited bacteria development: Quick freezing lowers the product’s temperature rapidly, giving bacteria less time and fewer opportunities to develop.

3. Prevention of enzyme effects: Enzymes can form in the product and cause it to ripen. Quick freezing can reduce the ripening of the product caused by enzymes.

4. Smaller ice crystals: Quick freezing avoids the formation of large ice crystals in the food’s cells. This prevents cell damage during thawing and prevents water from leaching out.

5. Increased productivity and profitability: Quick freezing can boost the hourly output of frozen products in a factory, leading to reduced utility costs for freezing food. The quality of frozen food improves, enhancing the overall value. Food processors using IQF generally experience higher profitability compared to those who don’t.

Several Options of IQF Freezer

Spiral Freezer

A spiral freezer consists of a spiral conveyor, evaporator, fans, insulated enclosure, and control system. It is the most popular type of IQF freezer and also the most versatile. The products that can be frozen by a spiral freezer include seafood, chicken parts, ready-to-eat meals, bakery dough, and more. The freezing capacity can range from 500 kg to 7000 kg/hr, covering the needs of most frozen processors. Due to the multiple belt levels in a spiral freezer, it can make the best use of space. Typically, with the same freezing capacity, a spiral freezer occupies less footprint than other IQF freezers, such as tunnel freezers or fluidized bed IQF. 

Click the link below for the spiral freezer video

Linear Tunnel Freezer

The working principle of a linear tunnel freezer is similar to that of a spiral freezer. The major difference lies in the configuration of the freezing chamber: the tunnel freezer features a linear belt conveyor, whereas the spiral freezer utilizes a spiral conveyor. As the tunnel freezer has only one level of a linear belt, its length typically ranges from 8 meters to 20 meters. The longer the belt, the larger the capacity. The most common freezing capacity of a tunnel freezer is between 200 and 1000 kg/hr. For larger capacities, the spiral freezer is preferred over the tunnel freezer due to its more compact design. The tunnel freezer is suitable for freezing seafood, chicken parts, ready-to-eat meals, bakery dough, and more. It is also more cost-effective than the spiral freezer, making it suitable for small frozen food processors to start with.

Click the link below for the linear tunnel freezer video

Fluidized Bed IQF Freezer(for fruits and vegetables)

Food particulates, generally of uniform size, are placed on a mesh conveyor. The airstream flows in an upward direction, and the air velocity is adjusted to just lift the product off the belt, causing it to flow. As the conveyor elevation changes, the solid particles begin to behave like a fluid as they are immersed in the air.

As the product moves in the fluidized bed, it comes into good contact with the air, facilitating excellent heat transfer between the air and the product.

Convective heat transfer coefficients of between 30 and 60 W/m2K can be achieved.

The product remains separated during freezing, with each particulate lifted off the belt and tumbling in the air. It freezes while remaining separate from neighboring particles, a process known as Individual Quick Freezing (IQF). Similar results can be achieved on a regular belt freezer, but in a fluidized bed, there is better separation of particulates, leading to individual quick freezing.

Common products frozen in a fluidized bed freezer include strawberries, blueberries, diced meat, peas, beans, and French fries.

About Square Technology Group Co. Ltd

Square Technology Group Co. Ltd is the largest IQF freezer manufacturer in China with over 37 years of experience. The product line includes spiral freezers, plate freezers, tunnel IQF, refrigeration systems, cold storage, air coolers, insulated panels, cookers, ovens, ice machines, etc.

Contact ntfe@ntsquare.com to learn more about IQF freezer products. Visit the website for additional information.