Case study on steam-assisted solvent-free microwave extraction of black pepper essential oil: Comparative performance, kinetics, and process intensification against microwave hydrodistillation

Steam-assisted solvent-free microwave extraction (SFMES) has been proposed as an intensified alternative to microwave hydrodistillation (MHD) for essential oil recovery; however, comparative engineering evidence under harmonized operating conditions remains limited. This case study evaluates and compares the extraction performance, kinetics, and process intensification characteristics of SFMES and MHD for black pepper ( Piper nigrum L.) essential oil production. Both extraction routes were investigated under identical microwave power (150–600 W), feed loading, and extraction time windows using a Taguchi L 32 experimental design. Extraction yield, recovery relative to Soxhlet reference, start-up dynamics, and physicochemical quality (ISO 3061:2008) were assessed, supported by GC–MS compositional analysis and kinetic modeling. The results demonstrate that SFMES consistently achieved higher oil yield and recovery, reaching up to 90.14 % Soxhlet-equivalent recovery, compared with 73.37 % for MHD at 600 W. Steam assistance significantly reduced first-drop time, stabilized thermal behavior at elevated microwave power, and enabled earlier attainment of extraction plateaus. Kinetic analysis revealed that SFMES followed Elovich-type behavior, indicating surface-controlled desorption, whereas MHD obeyed Power-Law kinetics characteristic of diffusion-limited liquid-phase transport. GC–MS analysis confirmed improved preservation of monoterpene-rich fractions under solvent-free steam-microwave conditions, while both methods produced oils compliant with ISO quality specifications. Hence, this case study demonstrates, using black pepper essential oil as a representative system, that steam-assisted solvent-free microwave extraction represents a practical and scalable process-intensification route for essential oil production, offering reduced processing time, improved recovery efficiency, and enhanced product quality relative to microwave hydrodistillation. • Steam-assisted SFME intensifies extraction by eliminating liquid-phase mass transfer. • SFMES delivers faster kinetics and higher oil recovery than microwave hydrodistillation. • Kinetic analysis confirms a shift from diffusion to vapor-driven desorption control. • Solvent-free steam–microwave coupling reduces energy and water consumption. • The framework enables cleaner and intensified microwave-assisted separations.