Effect of microwave power and extraction time on the yield of highly-valuable vegetable oil and microstructure during microwave-assisted extraction of roselle seeds

The increasing demand for healthy vegetable oils has encouraged researchers around the world to find their new and sustainable sources. In addition, the needs for more efficient and environmentally benign technologies for vegetable oil extraction has also received more attention from both researchers and industries. This study aims to investigate the influence of microwave on the extraction yield and microstructure of roselle seeds as a promising candidate of vegetable source. The extraction was performed using conventional Clevenger apparatus employing a microwave oven as the heating equipment at various microwave power and extraction time. The results show that increasing microwave power accelerated the release of oil from roselle seeds and subsequently shortened the extraction time. Microwave power also demonstrated its role to alter roselle seeds microstructure. The microwave-assisted extraction of vegetable oil from roselle seeds required a roselle seeds mass to solvent volume ratio of 1:6 and microwave power of 400 W for 20 minutes to successfully achieve 16.03% % yield. Further research on the roselle seeds oil composition and physical properties may be necessary to provide a more comprehensive information on the roselle seeds oil, extraction method, physicochemical properties, and applications.