What’s the Difference Between IQF and Cold Storage Freezing?

In the food processing and storage industry, refrigeration technology is crucial for maintaining product quality and safety. Two common freezing techniques used in this sector are Individual Quick Freezing (IQF) and cold storage freezing. What are the differences between these two methods? This article will compare the principles, features, and applications of IQF and cold storage freezing, helping you understand their distinctions better and choose the most suitable freezing technology to meet your needs.

Refrigeration Technology

Based on Working Principles

IQF (Individual Quick Freezing)

IQF (Individual Quick Freezing)

IQF is a specialized food freezing technology where each individual unit of a product is rapidly frozen separately. After freezing, the units do not stick together. For example, using IQF technology to freeze berries ensures each berry is completely frozen without clustering like ice cubes.

An IQF unit typically consists of an inlet section, a quick-freezing tunnel, freezing equipment, an air circulation system, and an outlet section. In the inlet section, a combination of conveyor belts and vibrating screens evenly distributes food products to prevent stacking and remove surface moisture. As food enters the quick-freezing tunnel, high-speed cold air rapidly removes heat from the food surfaces, achieving rapid freezing.

Cold Storage Freezing

Cold storage freezing is another common freezing technique where appropriate refrigeration units rapidly lower the temperature inside a cold room to very low levels, achieving quick freezing. Unlike IQF, cold storage freezing does not individually freeze each unit; instead, frozen products may develop large ice layers around them, causing units to stick together.

A cold room primarily consists of insulation materials and a refrigeration system. Food products are typically stacked or palletized inside the cold room. The refrigeration system lowers the temperature inside the cold room, facilitating freezing.

Freezing Speed

IQF Technology: IQF technology freezes food very quickly, often completing the process in just a few minutes.

Freezing Speed

Cold Storage Freezing: In contrast, cold storage freezing is relatively slower and depends largely on the choice of refrigeration equipment. Under similar conditions, the type and quantity of refrigeration equipment affect freezing speed. Even in quick-freeze cold rooms, it typically takes 2-4 hours to completely freeze food.

 

Based on the Quality of Frozen Products

Chemical and Physical Changes During Freezing

During the freezing process, food undergoes a series of chemical and physical changes that can adversely affect its quality. Here are some common chemical and physical changes that occur during food freezing:

Formation of Crystals

During the freezing process, the moisture inside the food solidifies into fine ice crystals. As freezing continues, these fine crystals may grow into larger, slow-frozen crystals. These larger ice crystals can damage the cell structure of food, affecting its texture and making it feel rough in the mouth.

Fiber Structure Breakdown

Freezing can also cause the fiber structure within food to break down, resulting in a less firm texture and poorer mouthfeel.

Generation of Drip Loss

Generation of Drip Loss

Upon thawing, food often releases liquid known as drip loss, which is formed as ice crystals melt. This liquid cannot be reabsorbed into the food’s cell structure to restore its pre-frozen state. Drip loss not only contains water but also dissolved nutrients such as proteins, minerals, and vitamins, thereby impacting the overall quality of the food.

Dehydration

During freezing, the sublimation of ice crystals causes food to lose moisture. This dehydration not only dries out the food, particularly meats, and fruits, but also reduces its weight.

Color Changes

During the freezing process, oxidation and cell damage can cause color changes in food. Upon thawing, frozen food may exhibit altered coloration, diminishing its visual appeal. Different types of food react differently to freezing, resulting in varying degrees of color change. Typically, bright colors may become dull after thawing.

 

Impact of Cold Storage Freezing on Food Quality

In conventional freezing methods like cold storage freezing, food often undergoes the chemical and physical changes mentioned above, leading to a decline in quality. However, employing suitable freezing techniques can help mitigate these adverse effects. Shortening the freezing time significantly preserves the quality of frozen products.

Impact of IQF on Food Quality

Impact of IQF on Food Quality

Compared to cold storage freezing, IQF technology offers faster freezingpeeds. This allows for the formation of evenly distributed fine ice crystals during freezing, reducing damage to cellular structure and helping maintain the food’s texture. Additionally, IQF technology minimizes dehydration in food. Studies indicate that food processed with IQF typically experiences dehydration rates ranging from 0.3% to 2%, whereas food processed with cold storage freezing can have dehydration rates as high as 5% to 10%. Furthermore, IQF technology minimizes the oxidation process, thereby preserving the food’s original color to the greatest extent possible.

Overall, IQF technology enables frozen foods to retain their original quality to a greater extent compared to cold storage freezing techniques.

 

Based on Applications

IQF

IQF technology offers the advantages of fast freezing speed, excellent freezing results, and maintaining food quality. However, its drawbacks include higher equipment costs and complex maintenance requirements. It is primarily suitable for freezing small-sized foods and high-value processed foods such as small fruits, vegetables, and seafood. If high food quality is a priority, IQF technology is an excellent choice.

Cold Storage Freezing

Cold Storage Freezing

Cold storage freezing is characterized by its wide applicability, relatively lower equipment costs, and simpler maintenance. However, it has the drawback of slower freezing speeds, which can impact food quality to some extent. It is widely used for freezing large quantities and bulk-sized foods, is often applied extensively in the freezing of meat products.

 

Conclusion

IQF and cold storage technologies play crucial roles in food freezing and storage. They exhibit significant differences in freezing speed, product quality, and applications. When deciding which freezing technology to use, it is important to consider the advantages and disadvantages of both IQF and cold storage freezing, as well as the specific requirements of food storage.

 

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