Drying kinetics of lemon (Citrus lemon) seeds on forced-air convective processing

Abstract

The convective drying kinetics of Citrus lemon seeds at different air temperatures (60–160 °C, 0.3 m.s−1), as well as the effect of air velocity (v) and technology (tray and rotary drum (RD) drying), were investigated. Internal seed temperature profiles showed that most of the process would occur under internal mass transfer control. Each drying curve was fitted with a theoretical diffusion model to determine the effective diffusivity (Deff), and with nine empirical models. Deff were 0.65 × 10−10-13.10 × 10−10 m2.s−1 and the activation energy was 19.90 kJ.mol−1. Deff increased by 85% when v was raised by 50%; this effect was partially compensated by seed movement when using RD (62% increment). A two-term exponential model with arrangements over the pre-exponential terms demonstrated the complementarity of both terms in explaining the seed dehydration process. In addition, convective heat transfer coefficients were calculated (0.48–0.65 W.m−2 K−1). Overall, the results provide valuable kinetic parameters to characterize the dehydration process for further design and simulation of drying equipment.