Thin-Layer Drying Model of Rambutan (Nephelium lappaceum L.) Kernel and Its Application in Fat Extraction Process

Abstract

Abstract Rambutan (Nephelium lappaceum L.) kernels contain a high amount of fat and it has a potential to be used as a new alternative source of edible vegetable fat. Drying of fat seed can improve the fat yield and prolong the seed storage shelf life. Therefore the drying behaviour of rambutan kernels was investigated using a hot air dryer for 6 h at each of three temperatures, 45°C, 55°C and 65°C. Based on the coefficient of determination (R2) and root mean square error (RMSE), modified Henderson and Pabis model was found to be the best thin-layer drying model for rambutan kernels (R2 > 0.99 and RMSE < 0.02). The effective moisture diffusivity of rambutan kernels, estimated from a modified equation of Fick’s second law of diffusion, was 2.56 × 10–10 to 3.68 × 10–10 m2 s–1. The result of fat extraction significantly indicates the effect of low moisture rambutan kernels on the fat yield enhancing (P < 0.05).