Drying Kinetics and Quality Evaluation of Mace Under Solar, Vacuum, and Hot-Air Drying Methods

Abstract

This study explored the impact of different drying methods namely solar-biomass, vacuum, and hot-air drying, on the drying characteristics, essential oil, oleoresin, and lycopene contents of mace. The research highlighted the importance of optimizing drying techniques to preserve the quality and bioactive compounds of mace, a valuable spice derived from nutmeg. Work compared drying efficiency and quality retention across the three drying methods. Experimental setup utilized a solar-biomass hybrid dryer with supplementary heating, alongside vacuum and hot-air dryers at temperatures of 45°C, 50°C, 55°C, and 60°C. The methodology involved measuring moisture reduction from an initial 55%–60% to a final 7%–8%, with vacuum drying achieving this in 4 h, hot-air drying in 6 h, and solar-biomass drying requiring 18 h. The drying process exhibited a falling rate period, with vacuum and hot-air drying reaching a maximum drying rate of 1.06 g/g dry mass·h, compared to 0.97 g/g dry mass·h for solar-biomass drying. Results revealed that vacuum-dried mace at 60°C yielded the highest essential oil (7.92%) and oleoresin (19.55%) contents, while hot-air-dried mace at 55°C had the lowest essential oil (7.63%) and oleoresin (18.44%). Solar-biomass-dried mace showed intermediate values (7.82% essential oil, 19.06% oleoresin). Lycopene content was highest in vacuum-dried mace (153.47 μg/mL), followed by hot-air (145.71 μg/mL) and solar-biomass (144.54 μg/mL) dried samples, indicating the superiority of vacuum drying in preserving bioactive compounds.