Microwave drying principle: Microwave refers to electromagnetic waves with frequencies ranging from 300 megahertz to 300 gigahertz. The dielectric material is composed of polar molecules (water molecules) and non-polar molecules. Under the action of an electromagnetic field, these polar molecules shift from their original random distribution state to orientation according to the polarity of the electric field. Under the action of high-frequency electromagnetic fields, these orientations change according to the alternating electromagnetic field, which causes molecular motion and mutual friction effects (under the action of a 2054 megahertz electromagnetic field, water molecules can make 2.45 billion displacements per second), thereby generating heat. At this point, the field energy of the alternating electromagnetic field is converted into thermal kinetic energy within the medium, causing the temperature of the medium to continuously rise. Microwave heating is a method of heating the object itself as a heating element, known as integral heating, which does not require a process of heat conduction and can achieve uniform heating in a short period of time. This feature can enable materials with poor thermal conductivity to be heated and dried in a short period of time, improve energy utilization, and make the size of the heating furnace smaller than conventional heating furnaces. Meanwhile, when the material is subjected to microwave electromagnetic fields, the overall temperature of the material increases. At this point, due to the evaporation of moisture on the surface of the material, the surface temperature decreases; This creates a temperature gradient that is high inside and low outside, and the direction of this gradient coincides with the direction of water evaporation. So the efficiency is extremely high. There are generally two ways in which microwaves are used for drying chemical powders. One is the conventional tunnel type drying equipment, mainly used for drying materials with low temperature requirements and no volatile substances generated during the process (it can dry to a moisture content of less than 0.1% in a few to ten minutes, and the temperature can be controlled within 100 degrees). The other is the microwave vacuum drying method (including static basket type microwave vacuum drying equipment and dynamic stirring type microwave vacuum drying equipment), mainly used for drying heat sensitive materials and volatile materials. Artificial nutritional rice is a substitute for ordinary rice, but it must be dried and sterilized during processing and manufacturing, so choosing microwave drying and sterilization equipment is also a choice.

Characteristics of artificial nutrition rice drying and sterilization equipment: After puffing and cutting, the rice is formed into a rough shape and then enters the microwave production line.

1. Uniform and fast. Heating both the inside and outside of the material at the same time, the material heats up quickly. There are no features such as condensation or stickiness on the surface.

2. Selective heating, water has a much greater heat absorption capacity than other dry materials due to its higher dielectric loss; At the same time, due to the fact that microwave heating is carried out both inside and outside, the internal moisture can be quickly heated and directly evaporated, allowing the material to be dried in a short period of time through heating. Simultaneously achieving sterilization effect and requirements.

3. High thermal efficiency. Due to the direct source of heat from the dried material, there is minimal loss of heat in the surrounding medium, and the microwave heating box itself does not absorb microwaves or generate heat. Most of the microwaves act on rice, resulting in very high thermal efficiency.

Technical parameters of artificial nutrition rice drying and sterilization equipment:

model: LT-100KW-SD

Power input: three-phase 380 ± 10% 50Hz;

Output trial load microwave power: 150KW (power adjustable)

Microwave input power: 100kw

Frequency: 2450MHz±50MHz

Equipment (length x width x height): 19800mm×1750mm×1650mm

Material import and export size: 80mm

Microwave leakage: in accordance with the national GB10436-89 standard ≤ 5mw/cm2

Compliant with GB5226 Electrical Safety Standard

Application of Microwave Industrial Drying and Sterilization in Agricultural Product Processing

1、 Overview

With the continuous improvement of people's living standards and changes in consumer attitudes, higher and higher requirements have been put forward for the product structure, quality, safety and hygiene of the food industry, especially for various traditional and convenient bag packaged foods, which have become a consumption hotspot in today's food market. However, during the production, storage, transportation, and sale of these foods, they are highly susceptible to contamination and spoilage, thereby losing their commercial value. Although the National Food Hygiene Law has strict regulations on hygiene indicators for various types of food, it is generally difficult to meet the standards. This not only greatly affects the shelf life of products, but also is extremely detrimental to safeguarding people's health. Although conventional techniques such as high-temperature drying, blanching, pasteurization, freezing, and preservatives can usually be used to achieve insecticidal sterilization and preservation of food. But most of these devices are large, have long processing times, incomplete sterilization or are difficult to achieve automated production, and often affect the original flavor and nutritional content of food. Microwave insecticidal sterilization is the process of subjecting microorganisms such as insects and bacteria in food to the combined effects of microwave thermal and non thermal effects, causing mutations in their proteins and physiological activity substances, resulting in delayed growth and development and death of microorganisms, achieving the purpose of food insecticidal, sterilization, and preservation.

2、 The mechanism of microwave nutrition rice drying, sterilization and preservation

Microwave sterilization and preservation aim to remove or kill microorganisms such as bacteria and worms in food after microwave energy treatment, ensuring that the bacterial content in food does not exceed the allowable range stipulated by the Food Hygiene Law during a certain storage period, thereby extending its shelf life.

The following is a brief description of the mechanism of microwave drying for sterilization and preservation: As is well known, bacteria, adults, and any biological cell are a cohesive medium composed of complex compounds such as water, ribonucleic acid, proteins, carbohydrates, fats, and inorganic substances. Water is the main component of biological cells, with a content of 75-85%, because various physiological activities of bacteria require the participation of water. The growth and reproduction process of bacteria, as well as the absorption of various nutrients, is completed through the diffusion and permeation absorption of cell membrane material. Under the action of a certain intensity of microwave field, insects and bacteria in food will also undergo molecular polarization relaxation and absorb microwave energy to heat up. Due to their being condensed matter media, the strong intermolecular forces intensify the conversion of microwave energy into thermal energy. Thus, the proteins in the body are subjected to both non-polar thermal motion and polar rotation, causing changes or damage to their spatial structure and resulting in protein denaturation. After protein denaturation, its solubility, viscosity, swelling, permeability, and stability will undergo significant changes, and it will lose its biological activity. On the other hand, the non thermal effect of microwave energy plays a special role in sterilization that conventional physical sterilization does not have, and is also one of the reasons for bacterial death. Microwave sterilization and preservation are the result of the combined effects of microwave thermal and non thermal effects. The thermal effect of microwaves mainly plays a role in rapid heating and sterilization; Non thermal effects, on the other hand, involve the mutation of proteins and physiologically active substances within microorganisms, resulting in loss of vitality or death. Therefore, microwave sterilization temperature is lower than conventional methods. In general, conventional methods require sterilization temperature of 120 ℃ -130 ℃ for about 1 hour, while microwave sterilization temperature is only 70 ℃ -105 ℃ for about 90-180 seconds.

3、 Characteristics of Microwave Drying for Sterilization and Preservation

1. Short time and fast speed

Conventional thermal sterilization involves transferring heat from the surface of food to its interior through methods such as heat conduction, convection, or radiation. It often takes a long time to reach the sterilization temperature. Microwave sterilization is the direct interaction between microwave energy and microorganisms such as food and bacteria, with both thermal and non thermal effects working together to achieve rapid heating and sterilization, greatly reducing processing time. The sterilization effect of various materials is generally within 3-5 minutes.

2. Low temperature sterilization maintains nutritional content and traditional flavor

Microwave sterilization is achieved through special thermal and non thermal effects. Compared with conventional thermal sterilization, it can achieve the desired disinfection and sterilization effect at lower temperatures and in a shorter time. Practice has shown that the general sterilization temperature can achieve the effect at 75-80 ℃. In addition, microwave treatment of food can retain more nutrients and flavors such as color, aroma, taste, and shape, and has a puffing effect. Vegetables treated with conventional heat retain 46-50% of vitamin C, while those treated with microwave retain 60-90%. Vegetables treated with conventional heat retain 58% of vitamin A, while those treated with microwave retain 84%.

3. Save energy

Conventional thermal sterilization often results in heat loss in the environment and equipment, while microwaves directly treat food without additional heat loss. In addition, its conversion efficiency from electrical energy to microwave energy is between 70-80%, while it can generally save 30-50% of electricity.

4. Uniform and thorough

Conventional thermal sterilization starts from the surface of the material and is then transmitted internally through heat conduction. There is a temperature difference between the inside and outside. In order to maintain the flavor of the food and shorten the processing time, the internal temperature of the food is often not sufficient, which affects the sterilization effect. Due to the penetrating effect of microwaves, when processing food as a whole, both the surface and interior are affected simultaneously, resulting in uniform and thorough disinfection and sterilization.

5. Easy to control

Microwave food sterilization treatment, equipment can be turned on and used immediately, without the thermal inertia of conventional thermal sterilization, flexible and convenient operation, microwave power can be continuously adjusted from zero to rated power, and transmission speed can be continuously adjusted from zero, making it easy to control.

6. Simple equipment and advanced technology

Compared with conventional disinfection and sterilization, microwave sterilization equipment does not require boilers, complex pipeline systems, coal yards, and transportation vehicles, as long as it has basic water and electricity conditions.

7. Improve working conditions and save land area

The working environment of the equipment has low temperature and low noise, greatly improving working conditions. The operator of the entire microwave equipment only needs 2-3 people. It is widely used in agaric, ginseng, flowers, artificial rice, nutritious cereals, rice, Rice noodles, onion, ginger and garlic slices. The heating, drying, and sterilization of products such as jujube slices, chili peppers, dehydrated vegetables, and soy products, through microwave sterilization and preservation technology, not only will the original nutritional components of the materials not be destroyed, but the hygiene indicators can be completely lower than the national food hygiene standards, and can fully meet the export level standards of food. It is the * drying and sterilization equipment for nutritional rice and artificial rice enterprises in China.