Microwave heating mechanism
Microwaves have a certain amount of energy (electromagnetic field energy). Under certain conditions, it can be used as an energy source.
Microwave has physical, chemical, biological and other effects on materials, and can be used for various purposes, but the most widely used one is microwave heating. This article mainly introduces this point.
Microwave heating is an extremely high-frequency electromagnetic oscillation that acts on the polar material molecules, causing the molecular arrangement and orientation to change drastically, resulting in an intense "friction" effect that heats the material. This process is the conversion of microwave electromagnetic field energy into heat energy.
Water molecules are polar molecules and strongly absorb microwaves. When a material containing moisture is subjected to strong enough microwave radiation, the water molecules in it absorb the microwave and quickly heat up and evaporate, and the material can be quickly dried.
Microwave sterilization is the result of the combined effect of microwave thermal effects and biological effects. The thermal effect of microwave on bacteria is to denature proteins, causing the bacteria to lose nutrition, reproduction and survival conditions and die;
the biological effect is that the microwave electric field changes the potential distribution of the cross-section of the cell membrane, affecting the concentration of electrons and ions around the cell, thereby changing the permeability of the cell membrane.
the bacteria are malnourished and cannot metabolize normally. The bacterial structure and function are disordered, and their growth and development are inhibited and they die. In addition, nucleic acid (RNA) and deoxyribonucleic acid (DNA), which determine the normal growth and stable genetic reproduction of bacteria, are coiled macromolecules tightly connected by several hydrogen bonds.
A sufficiently strong microwave field can cause hydrogen bonds to relax, break, and recombine, thereby inducing genetic mutations, chromosomal aberrations, or even breakage. Microwave sterilization makes use of the thermal and biological effects of electromagnetic fields to destroy organisms.
Therefore, the temperature of microwave sterilization is lower than that of conventional methods, only 70-105°C, and the time only takes about 3-5 minutes.
Microwave heating characteristics
Heating is rapid and uniform
no heat conduction process is required. It can penetrate the heated material in an instant. The penetration depth can reach several centimeters or even more than ten centimeters. It can convert microwave energy into heat energy in seconds to tens of seconds. Microwaves have selective heating, making heating more uniform.
Energy saving and high efficiency
Since materials containing moisture can easily absorb microwaves and generate heat, there is almost no other loss except a small amount of transmission loss. Compared with far infrared heating, microwave heating saves 1/3 of energy.
Anti-mold, sterilization and preservation
Microwave heating has thermal and biological effects, so it can kill mold and sterilize at lower temperatures; it can maximize the activity of materials and the vitamins, color and nutrients in food.
Advanced technology, capable of continuous production
heating or termination can be achieved as long as the microwave power is controlled. It has a complete conveying system to ensure continuous production, realize computer control and save labor.
Safe and harmless
Since the microwave energy is controlled in the heating chamber and waveguide made of metal, the microwave is effectively controlled. There is no radiation hazard or harmful gas emission, no waste heat is generated, and it neither pollutes food nor the environment. Improve working conditions.
service
The equipment occupies a small area and saves investment.
The application of microwave energy technology in food processing is not limited to drying, sterilization, and improving product quality; it also provides powerful new technological means for developing new products.
The use of microwave technology to transform and replace traditional processing methods has broadened the way for the development and production of new products. Fried foods, for example, cannot be declared "green foods" because they may contain a small amount of carcinogens.
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However, foods processed using microwaves instead of traditional frying processes (oil-free instant noodles, microwave puffed foods, etc.) have no carcinogen concerns. Another example is the freeze-drying method of dehydrated vegetables, which is of high quality, but the cost is high and the product is expensive, making it affordable for most people.
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The production of dehydrated vegetables in China mainly uses hot air drying, and the blanching process uses 80-90°C hot water, which causes the loss of many nutrients. Our company's first new method of combining microwave and hot air drying is used to produce dehydrated vegetables.
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The product quality is close to that of freeze-drying, and the cost is significantly reduced. Another example is that compared with the traditional extraction method, the microwave extraction process has higher extraction efficiency,
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The time is only a few tenths of the original method, reducing the consumption of energy, solvents and waste generation, and the equipment investment is only 1% of the carbon dioxide supercritical method extraction.
Conclusion
