Steam-assisted solvent-free microwave extraction of Melaleuca cajuputi oil: Process intensification and quality evaluation

Cajuput oil (Melaleuca cajuputi) extraction using conventional steam and hydrodistillation methods is typically associated with long processing times and high energy consumption, limiting process efficiency. Although solvent-free microwave extraction (SFME) offers faster extraction, it still suffers from non-uniform heating and restricted mass transfer in dense plant matrices. In this study, a steam-assisted solvent-free microwave extraction (SFMES) process was developed as an intensified alternative by incorporating controlled steam flow to enhance heat and mass transfer during microwave irradiation. This study presents the first integrated evaluation of SFMES for Melaleuca cajuputi oil that simultaneously combines process optimization, energy–emission analysis, and compositional selectivity within a unified cleaner engineering framework. The effects of key operating parameters, including microwave power, particle size, feed-to-distiller ratio, and extraction time, were systematically evaluated and optimized using Response Surface Methodology based on a Box–Behnken Design. Under optimized conditions, a maximum oil yield of 1.2 % was achieved with significantly reduced extraction time compared to conventional methods. Gas chromatography–mass spectrometry analysis confirmed a cineole-rich oil profile, while physicochemical properties complied with SNI 3954:2014 standards. From a cleaner engineering perspective, the optimized SFMES process exhibited low specific energy consumption (6 kWh kg⁻¹ oil) and reduced CO₂ emissions (4.8 g CO₂ g⁻¹ oil), outperforming both hydrodistillation and non–steam-assisted microwave extraction. These results demonstrate that SFMES effectively intensifies the extraction process by enhancing oil recovery, improving energy efficiency, and reducing environmental impact, suggesting its potential as a cleaner and industrially viable alternative for essential oil production.