IQF Freezing and Block Freezing: Differences and Applications

In the maritime and canning industry, there are various processes for treating raw materials like fish. Among these, freezing is a widely used procedure due to its advantages for transporting pieces and their subsequent commercialization.

In this article, we will discuss two of the most popular techniques: IQF (Individual Quick Freezing) and block freezing. We will then analyze their differences and diverse applications in the canning industry.

What is IQF Freezing?

IQF freezing, which stands for Individual Quick Freezing, is a freezing process used to preserve food items in separate pieces so that each unit is frozen independently and does not stick to the others. Unlike traditional methods that form compact blocks, IQF keeps products loose, facilitating their handling, storage, and consumption.

The IQF process involves exposing products to very low temperatures (typically between -30°C and -40°C) for a short period of time. This rapid freezing prevents the formation of large ice crystals within the food, which helps preserve its texture, flavor, and nutritional properties more effectively.

In the marine and fishing sector, IQF freezing is applied directly to products such as prawns, shrimps, mussels, squid rings, fish fillets, and also to small whole fish like sardines or other pelagics. Its use is particularly advantageous in these cases for several reasons:

• Preserves product quality: The rapid freezing process prevents cellular decomposition of the fish, resulting in better texture and flavor upon thawing.
• Prevents clumping: Each piece remains separate, making it easier to use portions of the product without needing to thaw the entire batch. The quality of each frozen piece is superior.
• Facilitates traceability and further processing: In canning or food processing plants, IQF allows dosing of the product as needed, optimizing production lines.
• Optimizes logistics: As only the required amount of product can be used, this reduces waste and improves inventory management.

IQF Freezing Machinery

In the industrial fishing environment, IQF machines are usually installed in onshore plants, although they can also be found on large factory ships. There are various types of IQF freezers, including tunnel freezers and fluidized bed freezers, where the product moves on conveyor belts through cold air streams that quickly freeze it.

Among all the machinery we manufacture at Gaictech, the brine IQF freezer stands out, specially designed for pelagic fish. This equipment has been designed to facilitate cleaning tasks thanks to its hydraulic system for lifting the conveyor system, providing full access to the freezing tank. Additionally, it features an agitator that keeps the brine in motion, preventing stagnation, which could otherwise slow down the freezing process.

IQF Freezing Applications

IQF freezing is commonly employed for fruits, vegetables, seafood, fish, and meats. This freezing method is highly appreciated for the flexibility it provides in both production and commercialization, allowing retailers to extract only the necessary quantity for sale without the need to defrost large volumes of product.

This method is commonly used in modern facilities aiming to make their business model more flexible, although its adoption also depends on the target market.

What is Block Freezing?

In block freezing, products are grouped and frozen together to form a compact block, usually rectangular or parallelepiped in shape. Unlike the IQF process, where pieces remain loose, in block freezing all units are enclosed within a solid mass of ice.

In this system, the product is placed into molds or containers, often along with water or another cryogenic substance, and then exposed to extremely low temperatures (generally -20°C or lower) for a prolonged period of time. The result is a rigid, uniform block that can be easily stored and transported.

In the fishing and maritime sector, block freezing is a widely used practice to preserve large volumes of fish, especially when efficiency in transportation and storage is prioritized. It is common in species such as sardines, mackerel, horse mackerel, and other fish caught in large quantities. Some of the advantages this method provides in the fishing context are:

• High storage density: By forming solid blocks, stowage in cold storage rooms and maritime containers is facilitated, optimizing the available space.
• Physical protection of the product: The ice block acts as a barrier against impacts and dehydration, protecting the food during transport.
• Long duration: By being kept frozen uniformly and compactly, the fish can be preserved for many months without significant loss of quality.

However, this process also entails certain disadvantages:

• Being a compact block, the defrosting process is much longer, which may affect the quality of some of the pieces that make up the block, depending on how careful (or not) the defrosting process is.

• Depending on how the fish grouping process has been to form the block, a significant percentage of deteriorated fish units may be achieved. Depending on the final market to which the fish is destined, this percentage of damaged fish may not be acceptable.

  This point, together with the mentioned defrosting issue, implies that block freezing might not be the most suitable if a process with quality product is desired.

• Possible problems: Fish with areas without skin, fish with burst stomachs or ventral areas, fish with forced ‘banana’ effect, etc.

Equipment and Technical Process

Block freezing is performed using specialized freezers known as plate freezers, which can be either horizontal or vertical. These machines compress products in metal trays and apply cold from multiple directions through refrigerated plates, by contact.

The freezing time depends on the thickness of the block, the type of fish, and the initial temperature of the product.

Another type of freezing tunnel is the blast freezer, also known as a conventional forced-air tunnel. In this system, the fish are grouped in molds or boxes that match the desired block size and introduced into the tunnel in an orderly, palletized manner. They are then exposed to a cold air stream, typically at -40ºC, until fully frozen.

Freezing times are longer compared to plate freezers, but the overall quality is better because there is no contact with the product.

Once frozen, the blocks are extracted and stored in cold storage rooms at sub-zero temperatures until transportation or processing. Upon arrival at their destination, industrial thawing systems are used to return the product to a processable state.

Conclusion

In summary, both freezing processes cater to different logistical and production needs. IQF offers greater versatility, quality, and convenience for later use, whereas block freezing is more efficient for storage and transportation. The choice between the two depends on the client’s specific commercial, technical, and logistical context.

Both methods are compatible with the processing lines that Gaictech offers and are integrated within a global strategy to ensure a continuous and adapted supply of raw materials to canning factories.