Evaluation of yields and quality parameters of oils from Cornus wilsoniana fruit extracted by subcritical n-butane extraction and conventional methods

Cornus wilsoniana fruit oil is a very important woody oil and is the main raw material of biodiesel. In this study, the oil yield, physicochemical properties, fatty acid composition, rheological properties, thermal stability, and Fourier transform infrared (FTIR) spectra of C. wilsoniana fruit oil obtained by subcritical n-butane extraction (SBE) and conventional methods such as pressing extraction (PE) and Soxhlet extraction (SE) were determined to study the influence of different extraction methods on the quality and yield of C. wilsoniana fruit oil. The oil yield of SBE (19.47%) was higher than that of PE (9.93%) but slightly lower than that of SE (21.08%). All of the extracted oils exhibited similar physicochemical properties, and the SBE oil was richer in polyunsaturated fatty acids (PUFA) than that of the PE oil, with an approximate 1:2 ratio of total saturated fatty acids against unsaturated fatty acids. The results of rheological behavior and thermal stability showed that all extracted oils had Newtonian flow characteristics, wherein the SBE oil exhibited lower viscosity and higher thermal stability. Furthermore, scanning electron microscopy (SEM) images of the surface topography indicated that different oil extraction methods will affect the residual oil content of the C. wilsoniana fruit powder. Compared with PE, the pores on the surface of the C. wilsoniana fruit powder after oil extraction were clearly visible, indicating that the driving force of SBE for oil extraction is stronger than that of PE. Based on the above results, it is implied that SBE is the best of the three methods for extracting C. wilsoniana fruit oil and can be potentially applied to extract other edible oils.