Radiofrequency Heating (RF)

Drying and thawing food

The dielectric radio frequency heating (RF)is based on the same principle as the microwave technology. The dielectric losses of the electromagnetic wave in a mixture of substances that result in the warming, depend on the dielectric constant of the material ε*. The dielectric constant of a substance consists of a real and an imaginary part (ε*=ε_r' - jε_r") and depends on both frequency and temperature. The dielectric loss factor tan δ= ε_r' / ε_r" is for the coupling of the electrical alternating field and thus responsible for the warming of the substance. The higher the tan δ, the easier it is to warm the substance.
Thus, for example, the tan δ of water is greatest at 22GHz, while he is almost zero at 27MHz. For frozen water, i.e. ice, it is the opposite. At 27MHz the dielectric loss factor is very high, whereas drops to very small values at 2.45GHz.
Therefore, the RF technology is particularly suitable for defrosting meat, fish, fruit and vegetables.

RF thawing plant for meat. Capacity 2000 kg meat / hour.

But RF systems are also used in the baking industry, e.g. for gentle drying of cakes and cookies after the baking process.

Drying plant for the bakery industry