Shandong Industrial Microwave Oven

1 microwave drying
Microwave is a high-frequency electromagnetic wave with a frequency of 300 MHz ~ 300 000 MHz and a wavelength of 0.001 m~1 m. Microwave drying is different from hot air and other drying methods. After microwave absorption, the food directly heats up, forming a small positive temperature gradient, which is conducive to the diffusion of internal moisture and greatly accelerates the drying speed. It is a new technology worthy of further study. The following describes the principle, characteristics and application status of microwave drying.

1.1 Principles and characteristics of microwave drying
The principle of microwave drying is: the microwave generator radiates the microwave to the dry material. When the microwave is injected into the material, the penetration causes the polar molecules such as water to rotate synchronously with the frequency of the microwave. For example, the dried vegetable products adopt RGS+DNO. Microwave, the polar molecules in the vegetables rotate R>GS billion times per second, and the polar molecules such as water rotate at such a high speed that the material instantaneously generates frictional heat, causing the surface and interior of the material to simultaneously heat up, making a large amount of water molecules. It escapes from the material and achieves the effect of drying the material.

1.1.1 Fast drying speed and short drying time
Since the microwave can penetrate deep into the material rather than by the heat conduction of the object itself, the heating time is very short and the drying time can be shortened by 50% or more.

1.1.2 High product quality
The microwave heating temperature is uniform, the surface is consistent, and the dry product can achieve uniform water distribution. Due to the selective heating of the water by the microwave, it is possible to dry at a lower temperature without causing the dry matter in the product to overheat and be damaged. Microwave heating can also produce some beneficial physical or chemical effects.

1.1.3 Responsive and easy to control
By adjusting the microwave output power, the heating of the material can be changed instantaneously, facilitating continuous production and automatic control, improving labor productivity and improving working conditions.

1.1.4 High heat utilization rate, saving energy, environmental protection, and low equipment footprint
Microwave heating equipment itself does not consume heat, most of the thermal energy (>80%) acts on the material, and the thermal efficiency is high, so energy saving, generally saves 30%~50%; has little effect on the ambient temperature, microwave drying equipment Can be done smaller.

1.1.5 Not paying for low temperature sterilization, maintaining food nutrition and flavor
Microwave heating has thermal and biological effects, so it can kill mold and bacteria at lower temperatures, maximizing the activity of the material and the vitamins, color and nutrients in the food. Microwave drying is often combined with hot air drying to increase the efficiency and economy of the drying process. Because hot air can effectively remove the free moisture on the surface of the material, microwave drying provides an effective method to eliminate internal moisture, and the combination of the two can exert their respective advantages to reduce the drying cost.

1.2 Development Status and Prospects of Microwave Drying at Home and Abroad
Guo Mei introduced the principle and characteristics of microwave drying and sterilization, and the microwave technology is continuously improving its technology and equipment. It is combined with other drying technologies, such as hot air drying, vacuum drying, freeze drying, and far infrared drying. A broader direction of development.

Shandong Industrial Microwave Oven elaborated on the principle, characteristics and application of microwave vacuum drying technology in the food industry. The problems existing in microwave vacuum drying technology were analyzed. The research status of this technology at home and abroad was introduced. Microwave vacuum drying is a new technology that combines the advantages of microwave drying and vacuum drying. It is very suitable for dry production of food. With the continuous improvement of computer monitoring technology and automation level of microwave vacuum drying equipment, microwave vacuum drying technology will be in food production. It is more widely used.

Shandong Industrial Microwave Oven discusses the performance characteristics of microwave drying equipment from the aspects of microwave drying heating characteristics and drying mechanism. According to the current situation of dryer market in China, it is considered that microwave drying is in the food industry, pharmaceutical industry and agricultural product processing. Excellent choice. Moreover, the performance and price ratio of high-power microwave drying equipment appearing on the market has been accepted by the majority of users.

Shandong Industrial Microwave Oven introduced a new type of computer automatic monitoring method, which can easily test the real-time temperature, weight and vacuum of materials in real time, and solve the problem of online monitoring of moisture content and internal temperature of materials during drying. Convenient online recording and query of test data and test results, achieving paperless recording, reducing the workload and human error of the tester.

Shandong Industrial Microwave Oven introduces the specific application of microwave drying in the drying of fruits and vegetables by taking some specific fruits and vegetables as an example. By comparing with other drying methods, the advantages and disadvantages of microwave drying in the processing of fruits and vegetables are compared. Based on the prediction of microwave drying technology in the future, it is recommended to accelerate the development of sophisticated automatic control systems and heat pump technology to improve the performance of drying equipment; develop heat recovery devices to improve energy efficiency; accelerate the promotion of microwave hot air drying technology; A combination of continuous microwave and traditional heating methods.

1.3 Summary
The development and application of microwave technology in developed countries has been in the past 20 years, but China is still in its infancy in this regard, mainly in the fields of chemical industry, wood, paper, food and so on. At present, there are not many equipments with perfect design and high degree of automation. The penetration surface is very narrow, and the potential market for microwave drying technology development is still very large.

2 spray drying
Spray drying is a drying method in which a liquid spray is sprayed into a mist by a sprayer to rapidly evaporate the moisture of the liquid. The application of spray drying technology has been more than 100 years old, but it started late in China. Since the earliest spray drying in 1865 for egg processing, this process of direct atomization and drying into a solid powder in a very short time has made great progress in the 20th century and is now widely used in food, Pharmaceutical, chemical, environmental protection and many other fields [8].

2.1 Spray drying in the food industry
Liu Jingbo, Ma Shuang, Lin Songyi et al. Prepared instant egg yolk powder by spray drying technology and studied the characteristics of egg yolk powder with different solubility. The rheological properties, particle structure and stability analysis were used to study the differences in the properties of egg yolk powders with different solubility levels. The results showed that the optimum conditions for spray drying of egg yolk powder were as follows: spray flow rate was 17.37 m L/min, feed temperature was 35.65 °C, and inlet air temperature was 185.36 °C. The average dissolution index of instant egg yolk powder was 1.850 6, solubility. The average is 98.74 g/100 g [9].

Shandong Industrial Microwave Oven explored the effects of spray drying process parameters such as decompression concentration and dehydration ratio, inlet air temperature and feed rate on the drying effect of the hydrolyzed protein solution of the almond and the antioxidant activity of the hydrolyzed protein powder. Mathematical model. The results showed that the almond starch hydrolyzed protein powder had certain antioxidant activity, but it was affected by the spray drying process parameters. The dehydration ratio was between 0.5 and 0.6, the inlet air temperature was about 200 °C, and the feed rate was 270 m L/h. At 320 m L/h, a better overall effect can be obtained [10].

Shandong Industrial Microwave Oven combines the current status of milk drying equipment and drying technology and dryers in China. The current status, application and development direction of milk powder drying equipment, namely spray drying equipment, are briefly described. The atomization structure and form of the spray drying equipment, the tower structure, the uniform wind, the exhaust, the powder, the powder form, the combination with other process equipment, and the automatic control system must be applied to the materials to be treated [11]. .

Shandong Industrial Microwave Oven analyzed the technical characteristics of microwave vacuum freeze-drying, as well as the problems of theory, process and equipment in the application, and proposed corresponding technical methods and means. The research and development of a microwave powder drying device integrating microwave technology, spray drying and freeze drying has realized the freeze drying of milk powder at -40 °C ~ -30 °C [12].

2.2 Development status and prospects of spray drying at home and abroad
Zhao Lixia discussed the application of spray drying process, spray drying equipment type and spray drying technology. It shows that the general spray drying includes liquid atomization, contact mixing of materials with hot drying medium, drying of materials, separation of dry products and drying medium. The application of spray drying in the pharmaceutical field, flue gas desulfurization, and papermaking black liquor treatment is introduced.

Shandong Industrial Microwave Oven proposed an improved method for spray dryers: improvement of hot blast stoves, increase of gun height, negative pressure in the tower, increase mud concentration, and improved nozzle structure. More than one year of application practice has proved that the improved spray drying tower has been put into production, and has achieved certain results in improving the quality, output and management of powder.

Zhang Caihong, Huang Lixin gave an overview of the development of spray drying in the processing and utilization of biomass resources from the aspects of process, mechanism, product quality and energy saving. It is found that there are still some problems in the research process, such as due to high intake air temperature. The product quality is degraded; the product sticking wall occurs in the drying chamber or the process tube; the system energy efficiency is low and the active material in the biological product is destroyed, etc., it is not necessary to improve and improve in the process and equipment, so it is necessary to spray drying technology Conduct more in-depth research.

2.3 Summary
The spray drying technology can dry the solution, suspension, emulsion, etc., and the obtained product has small particle size, uniformity, good fluidity and fast solubility, and has been widely used in many fields such as food, pharmaceutical, chemical, environmental protection and the like. It allows many valuable but difficult to preserve materials to greatly extend the shelf life, making some materials easy to package, store and transport. At the same time, it simplifies the processing of some materials. With the in-depth research and development of spray drying technology and equipment, spray drying technology will have broader application prospects.

3 vacuum freeze drying
Food vacuum freeze-drying equipment is a high-tech that uses low-temperature drying of fruits, meat, vegetables, edible fungi, concentrates and other foods to maximize the color, aroma, taste, shape and nutrition of food. Ingredients ensure the quality of the food.

3.1 Vacuum freeze drying in the food industry
Shandong Industrial Microwave Oven explores the application of vacuum freeze drying in fruits and vegetables. Shandong Industrial Microwave pointed out that freeze-dried foods avoid the defects of discoloration, odor, large loss of nutrients and poor rehydration caused by traditional dehydration methods, and maintain the original food shape, color, fragrance, taste, nutrition and rehydration. It has the advantages of light weight and storage at room temperature.

Shandong Industrial Microwave Oven et al. studied the application of vacuum freeze-drying technology in aquatic product processing, and found that the price of vacuum freeze-dried food is 4 to 6 times that of hot-air dried food, and 7 to 8 times the price of frozen food. It shows that the application of vacuum freeze-drying technology in China's aquatic product processing industry is feasible and has bright prospects.

Shandong Industrial Microwave Oven describes the principles of freeze-drying technology, process operations, the characteristics of freeze-dried foods and the application of freeze-drying technology in the food industry. The application range of vacuum freeze-drying technology in food processing, including vegetables, fruits, meat and poultry, aquatic products, health foods, beverages, food additives, etc., is pointed out.

3.2 Development Status and Prospects of Vacuum Freeze Drying
Shandong Industrial Microwave has conducted a corresponding discussion on food vacuum freeze-drying equipment. The design idea of the control system of food vacuum freeze-drying equipment was introduced in the aspects of control system control requirements, hardware structure of control system and preparation of control program.

Shandong Industrial Microwave introduced the composition and working principle of food freeze-drying equipment, discussed the development status of food freeze-drying equipment at home and abroad, and proposed the development trend of food freeze dryer, including improving structure, optimizing design, reducing cost and reducing Energy consumption, quality assurance, performance improvement, development of continuous freeze-drying equipment, and improvement of hygiene standards.

Shandong Industrial Microwave introduces food vacuum freeze-drying technology from the characteristics of freeze-dried foods, research status of food freeze-drying technology, freeze-drying process and application. Vacuum freeze-drying has unparalleled advantages in other drying methods, so it has become more and more popular since its inception, and has become increasingly popular in medicine, biological products and food.

Shandong Industrial Microwave introduced the advantages of food vacuum freeze-drying technology, reviewed the application status of food vacuum freeze-drying technology at home and abroad, and predicted the development prospect of food vacuum freeze-drying technology. Pointed out the freeze-dried foods that are being or are being developed abroad: new convenience foods, granular vegetables, powdered vegetables, etc.