Chemical composition and antioxidant activity of essential oils from barks of Pinus pumila using microwave-assisted hydrodistillation after screw extrusion treatment

Abstract

A screw extrusion treatment method successfully applies to the extraction of essential oils from Pinus pumila barks under microwave-assisted hydrodistillation conditions, which effectively promotes the increase of the yield of essential oils. Moreover, some potential factors affecting the yield of essential oils have been systematically analyzed and optimized through single factor screening method and Box-Behnken design, and the optimum operating conditions were liquid-solid ratio 5.82 mL/g, microwave irradiation power 585 W, and microwave irradiation time 30 min. Meanwhile, the satisfactory yield of essential oils was 16.51 ± 0.83 mL/kg in the derived optimum conditions, which was highly consistent with the predicted result (17.14 mL/kg) by the Box-Behnken design model. By comparing the kinetic curves of the separation of essential oils by different methods, the bark after the screw extrusion process can obtain higher yield and separation efficiency of essential oils through the microwave-assisted hydrodistillation method. The antioxidant properties and the yield of the essential oils separated by different methods were compared, and the antioxidant capacity and the yield of the essential oils obtained from the barks that were processed by screw extrusion treatment were significantly better than other treatment methods. By comparing the raw materials obtained by different treatment methods and their residues after essential oil separation, it was confirmed that the screw extrusion treatment method greatly increases the yield of the essential oils. The results show that the introduction of screw extrusion treatment and microwave-assisted hydrodistillation in the separation of essential oil has produced significant changes, which may become a new type of essential oil separation technology and be applied to the market.