Drying Kinetics and Mathematical Modeling of Algerian Red-Hot Pepper (Capsicum Annuum L.) Utilizing Microwave Radiation

Abstract

Background: Dehydration constitutes a fundamental preservation technique employed to reduce microbial proliferation and enzymatic spoilage in fruits and vegetables, thereby extending their shelf-life beyond the harvest season. While Capsicum annuum L. is a globally significant spice, its elevated moisture content renders it highly perishable in its fresh state.  Consequently, microwave drying has emerged as an advanced thermal processing method to address these stability issues efficiently.

Aims: This study aimed to characterize the drying kinetics of Algerian red-hot peppers subjected to varying microwave power levels. Furthermore, the research sought to identify the most suitable mathematical models to describe the drying behavior and optimize the process parameters.

Materials and Methods: Red-hot pepper samples were subjected to microwave drying at various power outputs. Moisture loss was recorded at regular intervals until equilibrium moisture content was achieved. Kinetic parameters were determined using established thermodynamic and mathematical equations and the experimental data were fitted to sixteen thin-layer drying models to evaluate their predictive accuracy.

Results: The results indicated that microwave drying time decreased notably from 80 to 24 minutes as power levels from 200 to 1200 . The process was characterized by two primary stages: an initial warming-up phase followed by a dominant falling-rate period. Drying rates () exhibited an initial progressive increase (0.1152 to 0.4012  for 200 and 1200 , respectively) followed by a significant decline during the final stages of dehydration. A third-order polynomial relationship was established to correlate effective moisture diffusivity ( with moisture content. ( increased significantly with microwave power as moisture content decreased (2.83 × 10^-8 ± 0.1834 to 12.9 ×10^-8 ± 0.2637  for 200 and 1200 , respectively). The calculated activation energy  was 23.48 ± 0.987 . While specific energy consumption () increased at higher power levels (1.55 ×10⁺⁸ ± 0.01 to 2.76 ×10⁺⁸ ± 0.0153  H₂O), the energy efficiency () displayed an inverse trend, decreasing from 14.55 ×10^-4 ± 0.0881 to 7.84 ×10^-4 ± 0.0078 %. Among the models tested, the Hii model demonstrated the highest statistical fit for describing the microwave drying kinetics.

Conclusions: Microwave drying offers significant technical advantages, including reduced processing time and optimized energy consumption when operated at moderate power levels. These findings suggest that this innovative dehydration process is highly suitable for industrial-scale food processing applications to enhance the quality and stability of Capsicum annuum L.

Keywords: Capsicum annuum L., drying kinetics, mathematical modeling, diffusion, energy activation, energy consumption.