ABSTRACT The dehulled and deseeded tamarind is used as an acidulant in cooking. The unit operations involved in the processing of tamarind are drying the whole tamarind fruit (WTF), dehulling, drying of dehulled tamarind, deseeding, and packing. The conventional industries are mostly using open sun dry method to dry the WTF which is time consuming and yield poor quality product whereas mechanical drying facilitates uniform drying and less time consumption. This study analyzed the drying characteristics of WTF having a complex structure, under open sun and tray dryer at varying temperatures of 50°C, 60°C, and 70°C. Moisture content (MC) trends over time were represented using polynomial equations specific to each drying method. These models offer predictions of moisture levels under given conditions. Standard thin‐layer drying models were applied to describe both natural and mechanical drying behaviors. Effective diffusivity, drying characteristics, activation energy and thermodynamics properties were explored. Under sun drying, the drying rate ranged from 0.0012 to 0.00360 g/g h, while in mechanical drying, drying rates varied from 0.0307 to 0.0024 g/g h at 70°C, 0.0297 to 0.00217 g/g h at 60°C, and 0.01307 to 0.00126 g/g h at 50°C. Higher drying temperatures resulted in faster moisture removal (70°C > 60°C > 50°C). Drying occurred entirely within the falling rate period, and no constant rate phase was observed. Equilibrium moisture content (EMC) after drying was recorded as 18.84%, 14.07%, and 13.86% (dry basis) at 50°C, 60°C, and 70°C, respectively. The Midilli et al. model was found suitable for the sun drying data, while the Jena‐Das, Midilli et al., and Verma models were suitable for 50°C, 60°C, and 70°C tray drying, respectively. Effective moisture diffusivity ( D eff ) ranged from 4.79 × 10 −10 to 6.91 × 10 −10 m 2 /s, and increased with drying temperature. The activation energy ( E a ) was determined to be 16.77 kJ/mol. Thermodynamic analysis revealed that the enthalpy change (Δ H ) ranged from 13.926 to 14.092 kJ/mol and decreased with increasing temperature. The Gibbs free energy change (Δ G ) remained high (167.880–175.320 kJ/mol), particularly at elevated temperatures, while the entropy change (Δ S ) ranged from −0.47599 to −0.47033 kJ mol/K and increased with rising temperature. The critical analysis on the drying behavior of WTF could be a great use for designing an exclusive dryer toward mechanizing the process flow.
Narasingam et al. (Sun,) studied this question.