A Comparative study on microwave dry-diffusion and gravity extraction method on the quality of rosemary essential oil

Abstract

Microwave dry-diffusion and gravity extraction (MDG) is an advanced microwave-assisted extraction technique. The aim of this study, was a comparison of different extraction methods namely MDG, microwave-assisted hydrodistillation (MAHD), and hydrodistillation (HD) methods and also evaluation of their effectiveness in isolation of essential oils from fresh Rosmarinus officinalis leaves. Variables such as extraction yield, extraction time, chemical composition, antioxidant activity, and operation cost were compared. The obtained results showed that the extraction times of essential oil by MDG, MAHD, and HD were 5, 15, and 120 min, respectively and energy consumptions were 0.04, 0.13, and 1.00 kW h, respectively. MDG offered important advantages over traditional HD method, namely increasing antioxidant activity (10.3%) and providing a more valuable essential oil components (α-pinene 17%, camphene 2.1%, and 1,8-cineole 2.8 % more than HD method). Gas chromatography/mass spectrometry analysis of the extracted essential oils indicated that microwave did not adversely influence the composition of the essential oils. In comparison with HD and MAHD, MDG required less energy, cost, and solvent. Hence, MDG can be proposed as a green and novel extraction technology.

Keywords

• essential oil
• extraction
• microwave
• rosemary