A Study on Drying Kinetics of Rhubarb Medical Plant by an Infrared Dryer

Rhubarb is a mountain plant that contains many antioxidants and various vitamins, including A, B۱, B۲ and C, and is an extremely healthy product and a rich source of antioxidants and dietary fibers. Today, it is important to dry medicinal plants and agricultural products in order to achieve better product quality, so that minimal physical, chemical and biological changes made in the product. In this research, the drying kinetics of rhubarb medicinal plant with an infrared dryer conducted at three temperature levels of ۵۰, ۶۰, and ۷۰ ℃ in the skin and without skin for ۲ and ۵ cm pieces of the product. By increasing the drying temperature and reducing the length of the parts and removing the skin of the samples, the drying speed and mass transfer increased and the drying time decreased. The values of activation energy ranged from ۳۲.۱۸ to ۴۵.۰۹ kJ/mol and the values of moisture diffusion coefficient ranged from ۲.۴۵ x ۱۰-۹ to ۵.۹۷ x ۱۰-۱۰ square meters per second. The overall color change of the product at all three temperatures was insignificant and the color of the rhubarb product changed little during the drying process. Using the intensity of low infrared radiations kept the color characteristics of rhubarb samples .Due to the low cost and high speed of drying, infrared dryer recommended as an economic method with high productivity for drying rhubarb medicinal plant.