Work

Mathematical Modeling of Moisture Diffusivity and Mass Transfer During Drying of Coffea arabica L. var. Catimor

Year: 2026

Type: article

Abstract: Understanding mass transfer mechanisms during coffee drying is essential for optimizing postharvest processing conditions. This study aimed to estimate the effective moisture diffusivity coefficient (Deff) and convective mass transfer coefficient (hm) of Coffea arabica L. var. Catimor through mathematical modeling. Drying experiments were conducted in an automated convection dryer (CE 130) at four constant temperatures (40, 50, 60, and 70 °C) and an air velocity of 1.5 m/s. Drying time, equilibrium moisture content (Meq), and critical moisture content (Mc) were determined. A MATLAB based algorithm was developed to solve Fick’s second law and estimate Deff and hm during coffee drying. An Arrhenius-type model was further applied to describe the temperature dependence of both coefficients. Although the model captured the general increasing trend with temperature, only moderate coefficients of determination were obtained (R2 = 0.63 for Deff and R2 = 0.74 for hm). Drying times were 26.5, 17.5, 16.5, and 13.5 h at 40, 50, 60, and 70 °C, respectively. Meq ranged from 11.30% to 11.76% (wet basis), while Mc remained close to 46% (wet basis) at all temperatures. Deff ranged from 0.232×10−10 to 1.397×10−10 m2/s, whereas hm ranged from 1.668×10−9 to 3.998×10−9 m/s. Both coefficients increased with temperature, indicating enhanced internal diffusion and external mass transfer. These findings provide useful engineering parameters for modeling, design, and optimization of industrial coffee drying processes.

Source: Agriculture

DOI: 10.3390/agriculture16131402