IQF Vs. Traditional Freezing Methods: A Comparative Analysis
May 28, 2023
May 28, 2023
Freezing is one of the most widely used methods for food preservation that allows locking texture, nutritional value and taste of food better than other methods. Over the years, different freezing methods have been adopted across industries with the advancement in technology. However, individual quick freezing (IQF) remains the preferred freezing method.
Let us discover how traditional freezing methods compare with IQF.
When it comes to the long-term preservation of fruits and vegetables, freezing is considered superior to canning and dehydration. Given the items being preserved are of high quality, GMP or good manufacturing practices are utilised in the preservation process, and the products are kept in the required temperature range, freezing helps extend the shelf-life.
Additionally, freezing requires the least processing time when compared in terms of cost, quality, and use of energy. Usually, freezing involves reducing the temperature of the product to -18 °C or below. However, dehydration and canning of fruits and vegetables require less energy than the freezing process and storage but the overall costs of freezing can be kept low or lower than other food preservation methods.
In summary, the benefits of freezing include the following.
The Indian Frozen Food Market stood at $1204.30 million in 2021 and is expected to grow with a CAGR of 8.00% to hit $1841.28 million by 2027. Growth in the e-commerce segment, increased demand for convenience food and processed food items, and changing lifestyles are some of the factors fueling the expansion of the Indian frozen food market.
During the freezing process, the product cools down below its freezing point but does not freeze. This phenomenon is known as supercooling. The product to be frozen is first cooled down to the temperature at which nucleation begins. Before the formation of ice, a nucleus (seed) is required upon which the crystals grow and this process is known as nucleation. Once the first crystal appears, the phase change takes place from liquid to solid to further increase crystal growth.
Image source: FAO
The freezing point is the temperature at which the first ice crystal appears and the liquid is in equilibrium with the solid. For instance, the freezing point of pure water is 0°C (273°K) but when food products are frozen, the process gets complex due to the presence of bound and free water.
Usually, the freezing process is divided into two categories.
Here is a quick glance at what the freezing process of fruits and vegetables looks like.
Image source: FAO
Before we dive into different types of freezing methods, let us determine the factors on which the choice of freezing method depends.
Here are different types of freezing methods.
One of the oldest methods of freezing, air freezing uses cool air with temperatures between -18 and -40°C. Commercially, there are three types of air freezing.
Air blast freezers recirculate cool air over foods between -30°C and -50°C at a velocity of 1.5 to 6 m/s. The airflow can be perpendicular or parallel to the food to ensure it flowers evenly all over the food products.
In this method, packaged items or fresh commodities are put on the surface of a plate that is cooled by a refrigerant in cylindrical scraped-surface heat exchange. Usually, double plates are used in retail storage.
In the liquid immersion freezing method, the product is immersed in or sprayed with a cold liquid such as glycol or brine while being conveyed through the freezer. Usually, the products are packaged to prevent any cross-contamination or contact between the liquid and the product. The liquid is refrigerated by circulation through a heat exchanger, cooling coils, or via a jacket built into the liquid tank.
This freezing method relies on the change of state of the refrigerants (cryogens) that absorb heat from the food being frozen. This heat provides the latent heat of sublimation or vapourisation of the cryogen which may include liquid nitrogen, solid carbon dioxide, and others. In cryogenic freezing, the cryogen is in close contact with the product and quickly removes heat from all surfaces, resulting in rapid freezing and high heat transfer coefficients.
|Freezers Type||Average Freezing Time
(Product thickness <100 mm)
|Plate Freezer||30 to 120 minutes|
|Air Blast–Batch Freezer||180 to 300 minutes or longer|
|Continuous Air Blast Freezer|
|Belt Freezer||20 to 30 minutes|
|Fluidized Belt or Tray Freezer||5 to 10 minutes|
|Cryogenic Freezer||½ to 1 minute|
Individual quick freezing is a special quick freezing method in which each and every product is frozen individually, even if multiple product types are frozen in the same area. For instance, every pea or each corn kennel is individually frozen and does not lump together.
Since this freezing method is ultra-quick, it does not allow large ice crystals to form in the fruit or vegetable cells, thus, maintaining the quality and shape of the frozen product. It rapidly lowers the temperature of the food to around -30 to -40℃ or even colder.
This method relies on blast freezing and is frequently used for berries, peaches, french fries, chicken, shrimp, salmon, peas, corn, fish, etc. Tunnel freezers and belt freezers are generally used for IQF of products. Additionally, it has low operational costs when compared to other liquid nitrogen freezers.
Some exclusive benefits of the individual quick freezing method.
The choice of freezing method depends on various factors including product type and size, freezing rate, specific heat, and many more. However, when compared to traditional freezing methods, individual quick freezing or IQF has emerged as a preferred choice in the food industry due to its short freezing time, quality output, and affordability.
Rinac, a market leader in cold chain processes offers straight (tunnel) and spiral belt IQF and each unit comes with a matching refrigeration package. To know more about technical specifications, get in touch with us today!
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