Generally speaking, the temperature for drying grapes should be between 40°C and 60°C, and the drying time should be determined according to the thickness and humidity of the grapes. If the temperature is too high, the surface of the grapes will dehydrate too quickly, and the internal water cannot be fully evaporated, making the outer layer of the raisins harden and the inside is humid; while the temperature is too low, the drying time will be too long, which will easily cause problems such as mold on the surface of the grapes. . Therefore, the best way is to experiment, observe the effect of grape drying, and adjust the temperature and time to achieve the best results before starting to dry.

1. Prepare grapes: Choose ripe, non-rotten grapes. You can wash the grapes with water and shake them dry.
2. Prepare the dryer: Adjust the heat pump dryer to the proper temperature and humidity. Generally speaking, the drying temperature of the heat pump dryer should be between 40-60°C, and the humidity should be between 30-50%.
3. Place the grapes: Place the prepared grapes evenly in the drying tray of the dryer.
4. Turn on the dryer: Turn on the dryer and set the drying time according to the instructions of the dryer. Generally speaking, the time for drying grapes needs to be determined according to the type, size and moisture content of the grapes. Drying time usually takes between a few hours and a day.
5. Check the grapes: During the drying process, you can periodically check the condition of the grapes to make sure they are not over-dried. If the grapes have dried, you can take them out.

In general, the temperature of the heat pump dryer should be between 40-60°C and the humidity between 30-50%. Different grape varieties and moisture content may require different drying times and temperatures. Therefore, before drying, it is best to know the characteristics of the grapes you are using and adjust the parameters of the heat pump dryer according to your needs.