Drying characteristics, color kinetics and quality evaluation of black pepper ( Piper nigrum ) under conventional and novel drying methods

Abstract This study investigated the drying characteristics and quality attributes of black pepper (var. IISR‐Thevam) under four methods: vacuum tray drying (VTD), infrared drying (IRD) and hot‐air drying (HAD) at 45, 50, 55, and 60°C, and sun drying (SD). Drying rate, effective moisture diffusivity, drying efficiency, color parameters (L*, a*, b*, hue angle, chroma, ΔE), and chemical constituents (essential oil, oleoresin, piperine) were analyzed. Infrared drying exhibited superior dry recovery (38.3% at 50°C) and drying efficiency (36.8% at 60°C), while vacuum drying at 60°C better preserved essential oil (2.9%), and color attributes. Essential oil contents of vacuum, infrared, hot air and sun‐dried black pepper were determined to be 2.9%, 2.9%, 2.6%, and 2.3%, respectively. Vacuum drying at 60°C and infrared and hot‐air drying at 55°C exhibited the maximum value for essential oil. Vacuum, infrared, hot‐air, and sun‐dried samples reported oleoresin and piperine contents of 7.55%, 7.55%, 7.5%, and 7.61% and 23.08, 21.08, 20.78, and 13.70 mg/mL, respectively. The highest value of oleoresin was observed at a temperature of 50°C for all three drying methods. Sun drying, despite being cost‐effective, resulted in the lowest retention of active compounds. Infrared drying balanced speed and quality, whereas hot‐air drying incurred greater color and nutrient losses. These findings highlighted the advantages of vacuum and infrared drying in enhancing the quality and marketability of black pepper, offering valuable insights for spice processors aiming to optimize quality, energy efficiency, and compliance with international trade standards.