Drying properties of agarwood leaves in vacuum far infrared dryer: Colour changes

Drying is the most common technique for preserving medicinal plants to increase the shelf life of medicinal plants. Drying techniques is one of the factors that change the quality of the product. Colour has played an essential role in the marketability of dried products. Colour is also vital in measuring the quality of phytochemical content in the dried material, especially medicinal plants. Agarwood or Aquilaria are endangered species under CITES that contain therapeutic benefits from their resin and leaves. Therefore, research on the usage of different drying techniques has been explored thoroughly to explore the benefits of this species. This study aimed to investigate the effect of Aquilaria Subintegra leaves by using a vacuum infrared dryer (VFIR) as an alternative drying technique using a radiation mechanism. The changes of lightness L*, a* and b* were observed during the drying under vacuum far infrared dryer. The combination of vacuum and infrared radiation helps in the accelerating the dehydration of moisture as well as the maintaining the appearance of the leaves at lower drying temperature. The usage of a vacuum far infrared dryer as an alternative drying technique that has excellent radiation characterises gave a better product's colour appearance with lower temperature and shorter drying time. (C) 2022 Published by Elsevier Ltd.