Development Prospect of Microwave Vacuum Drying Equipment

- May 08, 2019 -

Henan Microwave Equipment Network: Microwave vacuum drying equipment technology also has great potential in the field of food processing. At present, the microwave vacuum drying of shrimp has been tested, and the quality of microwave vacuum drying shrimp is compared with hot air drying and freeze drying shrimp. It is found that the shrimp dried by microwave vacuum drying is smaller than that dried by hot air drying, and has stronger ability of rehydration and moisture retention, and is close to rehydrated frozen shrimp in color, organization and flavor. The drying experiment of scallop was carried out in Henan Province by using self-made microwave vacuum drying equipment. The results showed that the color, aroma, taste and drying time of scallop after drying had reached ideal results. Microwave drying technology is a new technology and new method in drying industry. It can overcome many drawbacks of ordinary drying methods and cause extensive praise from users. Conventional drying methods, such as steam drying and far-infrared drying, use the characteristics of heat conduction to transfer temperature to the interior of the material, which will form a drying process, that is, the outer layer of the material is dried first, and then the drying layer moves inward gradually. Microwave has strong penetration and can overcome the above weaknesses. When the material meets microwave, both inside and outside will be heated at the same time, which avoids the problem of poor thermal conductivity of some materials and greatly improves the drying speed. In addition to the fast drying speed, the energy saving effect of microwave drying is considerable. For general materials, the less water content, the worse thermal conductivity. Thus, the outer drying layer forms a barrier to hinder heat transfer inward. The drying time is greatly prolonged. For example, wood, thermal insulation materials, honeycomb ceramics and so on, the drying speed can be increased by tens of times.

Water is a substance with strong molecular polarity and is more susceptible to microwave heating. Therefore, the higher the water content, the easier the substance to absorb microwave, the faster the heat is generated. When the water content decreases, the ability to absorb microwave decreases accordingly. Generally, in the early stage of drying, the moisture content of materials is higher, and the microwave power has a higher influence on drying effect. Continuous microwave heating can be used. At this time, most microwave can be absorbed by water, and the moisture can be rapidly transferred and evaporated. During the period of constant and decelerated drying, with the decrease of moisture, the microwave energy required is also less, so pulse gap microwave heating can be used. In general, microwave drying can save more than 30% energy than infrared drying, and the less water content, the more obvious the effect. Some materials, such as glass, ceramics, plastics, and some foods, absorb little microwave, while water absorbs microwave easily, so energy will be concentrated on water to the maximum extent. Microwave sterilization and drying equipment has the characteristics of selective heating of substances.

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