Hot-air and vacuum drying technology of celery

Celery was processed by hot-air drying combined with vacuum drying. The impacts of the drying conditions, such as the temperature of the hot-air, intermediate conversion moisture content, pressure, vacuum chamber temperature, drying time, and re-hydration ratio, on drying of celery were experimentally evaluated to optimize the drying procedures. The preliminary results show that the drying time decreased with the increase of the temperatures of both the hot-air and the chamber, but increased with the increases of the pressure and intermediate conversion moisture content. The optimized drying conditions include: the intermediate-conversion moisture content (w. b.) of 39%, a hot-air temperature of 67°C, a chamber temperature of 60°C, and a pressure of 20 kPa.