Supercritical fluid extraction of essential oil from mint leaves (mentha spicata): Process optimization and its quality evaluation

Supercritical fluid extraction of mint leaves was carried out at different process parameters using central composite rotatable design. The effects of temperature (35–55 °C), pressure (100–300 bar), dynamic time (20–90 min), and particle size (0.2–1.0 mm) were evaluated with respect to essential oil yield and carvone content in volatile oil. The particle size was found to have the most significant effect (p < 0.05) on essential oil yield followed by pressure, temperature, and dynamic time. Although in case of carvone content, pressure showed the most significant effect (p < 0.05) followed by particle size and dynamic time. The optimized SFE process parameter obtained though numerical optimization was 48 °C, 151 bar, 0.40 mm and 37.5 min, respectively having essential oil yield of 1.4%, carvone content of 998 mg/100 g and desirability value of 0.53. Quality of essential oil of mint obtained by SFE was compared with hydrodistilled oil. The essential oil obtained using SFE showed highest antimicrobial activity against E. coli and a moderate activity against S. typhi and S. aureus. PRACTICAL APPLICATIONS: The optimization of SFE process for mint oil extraction using response surface methodology approach is presented in the present study. The data obtained can be useful for scale up of batch scale SFE extraction of mint oil to a pilot or large scale system. A quadratic polynomial equation was developed, which can predict the oil yield as well as carvone content of mint leaves within the studied domain of the experimental SFE conditions. From the results obtained from this study, SFE can be used in industry for producing mint oil having high carvone content. The recommended operating condition for mint oil extraction is temperature 48 °C, pressure 151 bar, particle size of mint leaves 0.40 mm and dynamic extraction time of 37.5 min.