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How RF Tempering Achieves Unparalleled Temperature Uniformity Over Microwave Tempering

Updated: Jul 5, 2023


When it comes to tempering methods in food processing, two options are Radio Frequency (RF) and Microwave (MW) technologies. While both utilize endogenous or volumetric heating, there are distinct advantages to using RF tempering over microwave tempering in terms of temperature uniformity in the processed product. In this blog, we will explore the unique features of RF technology and equipment that make it the preferred choice for many food processing applications that require uniform defrosting.

Working Frequency and Penetration Depth

RF operates at frequencies in the range of tens of megahertz, commonly around 27 MHz. On the other hand, MW operates at much higher frequencies, typically in the range of thousands of megahertz or gigahertz, with 2,450 MHz being the most common frequency used in industrial and domestic MW equipment. The significant difference lies in their penetration depth, where RF waves can easily penetrate dense materials up to a depth of about 1.1 m (1/10 of their wavelength). In contrast, MW can only penetrate typically in the range of 1.2 centimetres , limiting their ability to uniformly heat products larger than a few centimetres, such as frozen blocks of meat, poultry or fish. Although lower MW frequencies can be used to improve penetration, they are subject to special permissions and compatibility issues. RF technology, therefore, offers the advantage of versatility, allowing for the heating of products of virtually any dimension.

Energy Transfer and Heating Uniformity

In addition to limited penetration depth, MW heating often results in uneven temperature distribution within the product. MW energy is generated by magnetrons and delivered to the product through waveguides which can lead to irregular energy absorption depending on the position and geometry of the product within the cavity, causing uneven treatments and temperatures. To address this, MW equipment incorporates mechanisms such as rotating plates or conveyor belts to keep the product moving. However, these efforts cannot guarantee precise and uniform energy transfer, often affecting the final result.

On the contrary, RF technology provides a solution to these challenges. The energy for the treatment is applied by a pair of electrodes. These electrodes, acting as opposite plates of a capacitor, receive energy from the generator and evenly distribute it to the product. As a result, regardless of the product's shape or size energy is absorbed evenly and diffusely. This controlled energy transfer mechanism in RF tempering leads to consistent and uniform heating, ensuring high-quality results.

Figure 1.0 Microwave Irradiation

Figure 2.0 Uniform RF Electric Field


While both RF and MW technologies offer endogenous heating methods for food processing, RF tempering stands out with its unique advantage of uniform defrosting. The ability of RF waves to penetrate large products and the even distribution of energy through controlled electrode-based heating make it the preferred choice in many applications. Whether you're tempering meat, poultry fish of dairy, RF technology provides a versatile and efficient solution for achieving uniform and precise heating in your food processing operations.


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