Drying of kaffir lime leaves in a fluidized bed dryer with inert particles: Kinetics and quality determination

• Drying kinetics of kaffir lime leaves in fluidized bed dryer was investigated.
• The presence of inert particles enhanced the drying rate.
• Fluidized bed retained the vitamin A and C contents and color of kaffir lime leaves.

Kaffir lime (Citrus hystrix D.C.) leaves are widely used as aromatic herb and food ingredient. Drying process is required to preserve this product. In the present study, drying behavior of kaffir lime leaves was investigated in a fluidized bed dryer with sand as inert particles under different superficial air velocities (0.6, 0.7 and 0.8 m/s) and mass ratios of kaffir lime leaves to sand (without inert, 0.04, 0.02 and 0.01) at a constant temperature of 50 °C. Effects of air velocity and mass ratio of kaffir lime leaves to sand were studied. The results showed that the rate of drying increased with increasing superficial air velocity. It was found that the presence of inert particles enhanced the drying rate. However, the rates of drying decreased when higher ratios of kaffir lime leaves to sand were used. Page model was the most suitable model to represent the drying kinetics experimental results with the highest r2 and the lowest RMSE values compared to the other drying models. The effective moisture diffusivity was found to increase with the increase in air velocity. Within the range of variables used, the values were reported to be varied from 2.61 × 10−11 to 9.24 × 10−11 m2/s. Comparison was made for the products dried using different drying methods (fluidized bed, sun and oven) in terms of color, composition of essential oil and vitamin C and A contents. No significant loss in the composition of essential oil, vitamin C and A contents and the color of kaffir lime leaves when drying in the fluidized bed dryer.