Solvent-free microwave extraction and microwave-assisted hydrodistillation of essential oils from spices

Thesis Type: Postgraduate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Engineering, Department of Food Engineering, Turkey

Approval Date: 2007


Supervisor: SERPİL ŞAHİN


The undesirable effects of conventional methods generated the need for economical and safe techniques in the extraction of essential oils. Microwave-assisted hydrodistillation (MAHD) and solvent-free microwave extraction (SFME) are recently developed techniques, which are thought to overcome this problem. Oregano (Origanum vulgare L.), laurel (Laurus nobilis L.) and rosemary (Rosmarinus officinalis L.) were chosen in this study since they have high antimicrobial and antioxidant effects and are widely grown and consumed in Turkey. The objectives of this study were to examine the applicability of SFME in the extraction of essential oils from oregano and laurel, and MAHD in the extraction of rosemary essential oil. The effects of microwave power and extraction time on the yield, composition, and other quality parameters of the extracts were also investigated. Hydrodistillation was performed as control. SFME offered significantly higher essential oil yields (0.054 mL oil/g oregano) from oregano as compared to hydrodistillation (0.048 mL oil/g oregano). Conventional process time was reduced by 80%. Main aroma compound was thymol (650-750 mg thymol/mL oil). For laurel, no significant differences were obtained in yields (about 0.022 mL oil/g laurel) obtained by SFME and hydrodistillation. Process time was reduced by 55-60%. Main aroma compound was 1,8-cineole (630-730 mg 1,8-cineole/mL oil). In the case of rosemary, no significant differences were obtained in yields (about 0.026 mL oil/g rosemary) obtained by MAHD at 622 W and hydrodistillation. The process time was reduced by about 65%. Main aroma compounds were 1,8-cineole (430-500 mg 1,8-cineole/mL oil) and camphor (150-210 mg camphor/mL oil). Keywords: Solvent-free microwave extraction (SFME), Microwave-assisted hydrodistillation (MAHD), Origanum vulgare L., Laurus nobilis L., Rosmarinus officinalis L.