Microwave heating is a heating method that relies on the material to absorb microwave energy and convert it into heat energy, so that the material itself is heated at the same time. Commonly used microwave frequencies are 915MHz and 2450MHz. Due to its high-frequency characteristics, the microwave electromagnetic field changes periodically at an amazing speed of billions of times per second, and polar molecules in the material (typically such as water molecules, proteins, nucleic acids, fats, carbohydrates, etc.) absorb the microwave energy. , they are arranged in order under the action of microwave electromagnetic field, changing their original random distribution orientation. Under the action of high-frequency electromagnetic field, these polar molecules also do electric field polar motion at the same speed with the change of the alternating electromagnetic field, which will cause the movement and rotation of the molecules, resulting in frequent collisions between molecules and a large amount of frictional heat. , and manifested in the material in the form of heat, resulting in a rapid temperature rise, heating or curing of the material in a short period of time.

Microwave heating is that the dielectric material itself loses electric field energy and generates heat, which is completely different from other conventional heating methods. The traditional heating method is based on the principles of conduction, convection and radiation, so that the amount of heating is transferred from the outside to the material. The amount of heating is always transferred from the outside to the inside to add the material. There is inevitably a temperature gradient in the material, so the heated material is uneven. , resulting in local overheating of the material. Microwave heating is through the high-frequency reciprocating motion of the dipole molecules inside the heated body, which generates "internal friction heat" and increases the temperature of the heated material. Without any heat conduction process, the inside and outside of the material can be heated at the same time. The speed is fast and uniform, and the heating purpose can be achieved with only a fraction or tens of the energy consumption of the traditional heating method. From the theoretical analysis, the amount of heat generated by a substance in the microwave field has a great relationship with the type of substance and its dielectric properties, that is, microwaves have the property of selectively heating substances.

Principle of microwave sterilization:

(1) Thermal effect: Under the action of microwave, harmful bacteria, insect pests and other microorganisms in the material are affected by non-polar thermal motion and polar rotation to change their arrangement and combination state and motion law, resulting in changes in the structure of microbial protein. As a result, the biological activity is lost, so that the bacteria die or are seriously disturbed and cannot reproduce.

(2) Non-thermal effect: mainly the effect of alternating electromagnetic fields on living organisms. Change the biological arrangement, combination state and movement law of a large number of electrons, ions and other charged particles produced by microorganisms in the chemical process of their life. In addition, microwaves can also lead to the loosening, breaking and recombination of hydrogen bonds in cellular DNA and RNA molecular structures, interfering with or destroying their normal metabolism, and inducing gene mutations, thereby interrupting the normal reproductive capacity of cells.