When a microwave dryer dries food, it may cause some damage to the nutrients in the food. Microwave dryers use microwave radiation to generate heat energy to evaporate moisture from food to achieve the purpose of drying. However, this method of heating may result in the loss of some nutrients.

Some nutrients are heat-sensitive, such as vitamin C and B vitamins. At high temperatures, these nutrients may break down or become inactive, causing the nutritional value in the food to decrease. In addition, microwave dryers may cause some oxidation reactions to occur, thereby reducing the antioxidant content in food.

On the other hand, a microwave dryer can complete the drying process faster than traditional drying methods, which helps preserve some heat-sensitive nutrients. In addition, microwave dryers often keep food at a lower temperature during the drying process, which also helps reduce the loss of some nutrients.

In general, microwave dryers may cause certain damage to nutrients when drying food, but the specific impact will be affected by a variety of factors, such as drying time, temperature and type of food. To maximize the retention of nutritional value in food, it's best to use low temperature and short-time drying methods, or consider other gentler food preservation methods, such as freezing or vacuum packaging.