Process Optimization of Supercritical CO₂ Extraction for Enhanced Yield of Sarawak Black Pepper (Piper Nigrum L.) Essential Oil

Supercritical fluid extraction (SFE) using carbon dioxide has become a green and efficient alternative to traditional methods for extracting essential oils and bioactive compounds from plant materials. However, extraction performance heavily depends on operating conditions, requiring systematic optimization. In this study, a One Factor At a Time (OFAT) approach was used to optimize the supercritical CO₂ extraction of Sarawak black pepper (Piper nigrum L.) oil, aiming to maximize oil yield and retain key bioactive compounds. The effects of extraction pressure (200-325 bar), temperature (20-70 °C), CO₂ flow rate (2-10 g min⁻¹), extraction time (30-180 min), and ethanol co-solvent concentration (0-25% w/w) were examined individually while keeping other parameters constant. Oil yield was measured gravimetrically, and piperine content was analyzed using high-performance liquid chromatography. Results indicated that all operating parameters significantly affected extraction efficiency. The optimal conditions were found at 300 bar pressure, 50 °C temperature, 6 g min⁻¹ CO₂ flow rate, 90 min extraction time, and 10% (w/w) ethanol as a co-solvent. Under these conditions, a maximum oil yield of 4.07 ± 0.10% was obtained. The optimized extract had a piperine content of 4.88% (w/w) and physicochemical properties consistent with high-quality, unadulterated black pepper oil. Compared to Sarawak-specific SFE studies without co-solvents, adding ethanol significantly improved extraction efficiency. Overall, this study shows that OFAT-based optimization offers valuable parametric insights and provides a practical, scalable strategy for producing high-quality Sarawak black pepper oil using supercritical CO₂.