estimation of the mass transfer parameters of horseradish (armoracia rusticana l.) under convective drying

the glucosinolates in the horseradish (armoracia rusticana l.) have the potential to increase human resistance to cancer and environmental toxins. they have powerful antioxidant properties and can also be used to relieve sinus and respiratory distress. drying is the most common method of medicinal plant preservation and, due to high investment and energy costs, drying is also a large expense in medicinal plant production. drug quality and consequently earnings are significantly influenced by the drying regime. the design of the proper operating conditions relies on the knowledge of the transfer phenomena happening during drying. hence, the present work aimed at determining the mass transfer properties of horseradish for convective air drying, using fick’s second law of diffusion for slab geometry. the drying process for horseradish took place in the falling rate period. the values of the mass transfer coefficients and mass biot numbers were determined for the three drying temperatures, 60, 70 and 80˚c. the effective diffusivities, mass transfer coefficients and the mass biot numbers varied between 3.838×10^-9 to 5.388×10^-9 m²/s, 2.034×10^-6 to 3.589×10^-6 m/s and 2.649 to 3.115 for the air temperatures studied, respectively. the results obtained showed effective diffusivities and mass transfer coefficient increased with the increasing air temperature where as the mass biot numbers decreased with the increasing air temperature. also the mass transfer coefficient suffered a very important increase with temperature, owing to a higher efficiency of the moisture transfer at the surface of the horseradish.