The Extraction Mechanism of Essential Oil from Michelia alba DC. Using Subcritical Solvent Extraction

The use of essential oils from plants has occurred since ancient times, with their demand steadily increasing. In Southeast Asia, the white champaka flower is a well-known medicinal flower, and its essential oil holds significant value in various industries. There are numerous studies on enhancing their extraction yields using various methods. However, research into the extraction mechanism of the white champaka flower is relatively limited, despite their importance. Therefore, the study of essential oil extraction from Michelia alba D.C. or white champaka flowers was investigated using the subcritical solvent extraction method with 1,1,1,2-tetrafluoroethane (HFC-134a) as the solvent. This research analyzes the extraction mechanism and the effects of time and temperature on the extraction yield. The extraction times were varied to 20, 30, 40, and 50 minutes per extraction loop, and the temperatures ranged from 40°C to 60°C. The results showed that increasing time or temperature significantly improved the extraction yield. Furthermore, this study also provides an agitator as an alternative method for maintaining the solute concentration difference between the inside and outside of the raw material particles. This replaces the old method used in the machine, which is called the “solvent-overfill method”. Lastly, the extraction mechanism was analyzed using mathematical modeling, including Darcy’s law, the mass transfer equation, and the Arrhenius equation. Consequently, the initial concentration of solute inside white champaka petal, the activation energy and pre-exponential constant, were evaluated to be 6.99×10^-4 g/cm³, 18.48 kJ/mol and 9.03×10^-2 g/min·cm², respectively, as well as the mass transfer coefficient of the extraction at various temperatures. These discoveries are highly advantageous for further research on the extraction of other flowers under similar conditions.