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<p>Uneven heat distribution and overheating are common challenges in microwave (MW) drying, often leading to inconsistent product quality. This study aims to improve the heating uniformity of coffee beans during MW drying by developing a mixing mechanism consisting of two plastic tubes and a cross-shaped mixing blade integrated into the MW cavity. Experimental data were fitted to mathematical models to describe the drying kinetics. Semi-wet processed coffee beans were dried in a MW system operating at 330&#xa0;W (2450&#xa0;MHz) with controlled temperatures of 40–55&#xa0;°C. For comparison, a separate batch was dried in a conventional oven at 50&#xa0;°C. The drying process was terminated when the final moisture content reached 11–12% (wet basis). MW drying with the mixing mechanism achieved this target in 2&#xa0;h, significantly shorter than MW drying without mixing (5&#xa0;h) and oven drying (14&#xa0;h). Mixing improved heating uniformity by reducing temperature differences (ΔT) and the heating uniformity index (λ). Without mixing, surface temperatures exceeded 55&#xa0;°C (peaking at 64&#xa0;°C), exacerbating uneven heat distribution. The logarithmic model most accurately described the drying kinetics, which exhibited only a falling rate period. These results demonstrate that integrating a mixing mechanism into MW drying systems enhances heating uniformity and drastically shortens drying time for coffee beans. The findings underscore the potential of optimized MW technology to improve efficiency and consistency in food processing applications beyond coffee.</p>

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Drying coffee beans with an innovative microwave mixing system: heat uniformity and drying kinetics

  • 期刊论文

  • 发表日期：

    2025年9月26日

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  • Bandar Alfaifi,
  • Abdulrahim A. Mohamed,
  • Saleh Al-Ghamdi,
  • Isam A. Mohamed Ahmed,
  • Ahmad M. Salamatullah,
  • Fahad Al Juhaimi,
  • Mohammed Saeed Alkaltham,
  • Abdullatif Alwshigry,
  • Mansour Ibrahim

摘要

Uneven heat distribution and overheating are common challenges in microwave (MW) drying, often leading to inconsistent product quality. This study aims to improve the heating uniformity of coffee beans during MW drying by developing a mixing mechanism consisting of two plastic tubes and a cross-shaped mixing blade integrated into the MW cavity. Experimental data were fitted to mathematical models to describe the drying kinetics. Semi-wet processed coffee beans were dried in a MW system operating at 330 W (2450 MHz) with controlled temperatures of 40–55 °C. For comparison, a separate batch was dried in a conventional oven at 50 °C. The drying process was terminated when the final moisture content reached 11–12% (wet basis). MW drying with the mixing mechanism achieved this target in 2 h, significantly shorter than MW drying without mixing (5 h) and oven drying (14 h). Mixing improved heating uniformity by reducing temperature differences (ΔT) and the heating uniformity index (λ). Without mixing, surface temperatures exceeded 55 °C (peaking at 64 °C), exacerbating uneven heat distribution. The logarithmic model most accurately described the drying kinetics, which exhibited only a falling rate period. These results demonstrate that integrating a mixing mechanism into MW drying systems enhances heating uniformity and drastically shortens drying time for coffee beans. The findings underscore the potential of optimized MW technology to improve efficiency and consistency in food processing applications beyond coffee.