Abstract: Microwave drying equipment can effectively shorten the drying time and improve the quality of apple dehydration. Six constant temperature microwave drying schemes and three variable temperature microwave drying schemes were used to study the drying characteristics and quality of apples under different schemes.
The experimental results show that the drying rate of "constant temperature" drying scheme decreases slowly in the middle drying stage, which will result in lower quality of products. In the "drying rate control" scheme, the drying rate is controlled at a constant speed in the middle of drying, but there are some defects in the initial drying control; in the "linear temperature control" scheme, the drying rate is basically maintained at a constant speed in the middle of drying, and the drying time and energy consumption are reasonable, sensory quality and color quality are superior to the constant temperature drying; In the three-stage temperature control scheme, the complexity of the equipment used in the linear temperature control scheme is simplified. Although the product quality index is slightly decreased, the equipment is simplified, which is more conducive to industrial application. This study provides a technical basis for the application of microwave drying technology to Apple drying theory.
Key words: microwave drying, drying rate, temperature change, apple
Microwave drying technology is widely used in food industry because of its high efficiency and low energy consumption. In the process of Apple microwave drying, the electromagnetic wave emitted by magnetron directly acts on the ions and dipole molecule of the material, causing its vibration and mutual friction to produce heat, thus rapidly increasing the temperature of the object. If the magnetron stops working, the action of ions and dipole molecules in the object will stop immediately, and the temperature will drop faster than other ways of heating and drying from outside to inside. Therefore, by automatically adjusting the microwave power can quickly and effectively control the temperature of the object in the microwave drying process.
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