Microwave dryers are widely used in food processing. For example, the drying, sterilization and heating of chicken, duck, beef jerky, pork jerky and other products require microwave drying process. Food dried by microwaves still maintains its original flavor and its shelf life can be extended. When microwave drying food, packaging materials need to meet the following requirements:

1. Microwave transparency: Packaging materials need to have a certain degree of microwave transparency so that microwaves can penetrate the packaging, be absorbed by the food, and be converted into heat. Common microwave transparent packaging materials include cellophane, plastic film and special microwave transparent plastic.

2. Heat resistance: Since high temperatures may be generated during microwave drying, packaging materials need to have a certain degree of heat resistance to prevent the packaging from melting, deforming or releasing harmful substances during microwave heating.

3. Microwave absorptivity: Packaging materials should not be too microwave-absorbent to avoid absorbing too much microwave energy, causing the packaging materials to overheat or even ignite. At the same time, it is also necessary to ensure that the food can fully absorb microwave energy for drying.

4. Food safety: Packaging materials should comply with safety standards related to food contact to prevent harmful substances from penetrating into food.

5. Moisture resistance: Since some steam may be generated during the microwave drying process, the packaging materials need to have a certain moisture resistance to prevent the food from getting damp during the packaging process.

6. Uniformity of microwave heating: The shape and structure of the packaging should promote the uniformity of microwave heating to ensure that food can be heated evenly in the microwave field and avoid local overheating or overdrying.