Yuan Meng | ALES Graduate Seminar

Event details: A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Yuan Meng. This seminar is open to the general public to attend.

MSc with Dr. Marleny Aranda Saldana.

Thesis Topic: SC-CO2 Processing: Extraction, Scale-up and Impregnation of Essential Oil from Mentha Piperita

Abstract:

Mentha piperita is an important aromatic plant in the Lamiaceae family with great industrial potential. In the first study, the research aimed to explore the potential of supercritical carbon dioxide (SC-CO2) to extract essential oil from peppermint leaves as well as evaluate the scale-up of the extraction process. A systematic investigation of processing parameters such as pressure (100-400 bar), temperature (45-55 °C), CO2 flow rate (0.5 and 3 mL/min), time (15-180 min), and co-solvent type (ethanol, acetone, and isopropyl acetate) was undertaken to maximize extraction yield. Gas chromatography was employed to analyze the essential oil extracts, focusing on quantifying menthol and menthone contents. The DPPH and FRAP methods were also used to determine the antioxidant property of extracts obtained. The highest extraction yield (1.97%) was achieved at 400 bar and 50 °C for 120 min with a flow rate of 3 mL/min. However, superior essential oil quality, with the highest menthol content (47.50%) and menthone content (2.29%) was obtained at 110 bar and 50 °C for 120 min with a flow rate of 3 mL/min. Co-solvents enhanced the extraction yield, though they influenced the menthol and menthone contents in the extracts. Scale-up experiments resulted in yields of 0.94%, 0.79%, and 0.77% for 3-fold, 5-fold, and 10-fold increases in peppermint powder loading, respectively, at 110 bar and 50°C. In addition, these scale-up processes resulted in menthol contents of 49.81%, 48.186%, and 47.362% and menthone contents of 1.90%, 2.00%, and 2.13% in the extracts, respectively. Furthermore, peppermint essential oil exhibited antioxidant activity, displaying its most significant scavenging activity of 77.9% and a ferric reducing power equivalent to approximately 82.253 μM ascorbic acid equivalent at a concentration of 500 mg/mL. In the second study, the solubility of menthol in SC-CO2 was evaluated to further impregnate menthol on cotton gauze using SC-CO2. Solubility of menthol in SC-CO2 was carried out at various temperature (45-55 °C) and pressure (100-300 bar) conditions, with SC-CO2 density varying from 337.2 to 890.3 kg/m3. Overall, the best solubility of menthol was 1.2510-2 mole fraction obtained at 120 bar and 45°C. Then, the impregnation of menthol onto cotton gauze was accomplished using SC-CO2 at 120 bar and 45 °C, and a depressurization rate of 6 bar/min or 60 bar/min and a time of 30 min or 300 min. High impregnation yields ranging from 6% to 30.65% were achieved with the long impregnation time of 300 min and the lower depressurization rate of 6 bar/min. The impregnation process demonstrated the successful dissolution of menthol and penetration into the cotton gauze matrix. The FT-IR, SEM, and TGA analyses confirmed the effective impregnation of menthol without significant alterations in the cotton’s structural integrity. Overall, this study provides significant insights into peppermint essential oil extraction by SC-CO2, particularly relevant to the food and pharmaceutical sectors.

Keywords: Supercritical carbon dioxide processing; Extraction; Scale up; Mentha piperita; Menthol; Solubility; Impregnation.