Enhanced supercritical CO2 extraction of Xanthoceras sorbifolia Bunge seed oil

Abstract

Xanthoceras sorbifolia Bunge (XSB) is an emerging woody oil crop with great potential in edible oil and functional food industries, particularly due to its high nervonic acid content. However, current research on XSB mostly relies on conventional extraction methods, which have drawbacks like incomplete extraction and easy degradation of heat-sensitive components such as nervonic acid. A key academic gap is the lack of systematic exploration on green, efficient extraction technologies for Xanthoceras sorbifolia Bunge seed oil (XSBO), especially in optimizing advanced extraction parameters to balance oil yield. To fill this gap, supercritical fluid extraction of carbon dioxide (SFE-CO2), which is
also called supercritical CO2 extraction was adopted as the core method in this study. I initially explored the pressing preparation process of XSBO and determined the optimal pressing temperature. Firstly, SFE-CO2 was employed, and single-factor experiments combined with the response surface method (RSM) were conducted to optimize the process conditions for XSBO production. Based on this, the enhanced effects of extending extraction time, secondary extraction, and novel co-solvents on improving extraction efficiency were further investigated. The extraction yield, fatty acid composition, and content of XSBO under several different process conditions were analyzed and compared. For the purification of XSBO, multi-stage molecular distillation was studied, with the key objective of nervonic acid enrichment. Gas chromatography-mass spectrometry (GC-MS), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FT-IR)
were employed to analyze the oils and oil meals obtained from different processing technologies. Overall, enhanced SFE-CO2 combined with molecular distillation was proven to be a cost-effective and efficient strategy for producing high-quality XSBO, providing valuable theoretical and technical support for its industrial development. The main findings of the research are as follows:
(1) Mechanical pressing temperature had a significant effect on XSBO production. At 200 °C, the oil yield reached 85.1 % ± 0.2 %, indicating that pressing is feasible but limited by lower extraction efficiency compared with other methods.
(2) Single-factor experiments and RSM were used to optimize SFE-CO2 conditions. The optimal parameters were an extraction pressure of 31 MPa, temperature of 45 °C, and time of 120 min, resulting in an oil yield of 91.25 %.
(3) Three enhancement strategies were tested for SFE-CO2: prolonged extraction time, sequential extraction, and the addition of novel co-solvents. These approaches improved oil yield up to 98.7 % and slightly modified the physicochemical properties, suggesting their potential for industrial-scale improvement.
(4) Multistage molecular distillation effectively enriched nervonic acid in XSBO. From the first to the third distillation stage, nervonic acid concentration increased from 20.64 mg/mL to 28.34 mg/mL, while maintaining good oil quality indicators.
(5) Analytical characterization confirmed that the oil composition obtained by different processes exhibited little variation. Meanwhile, GC-MS confirmed the fatty acid composition of XSBO, SEM observations revealed the microstructural changes of seed kernels powder before and after extraction, and FTIR spectroscopy identified the characteristic functional groups of the seed meals, further demonstrating the good quality stability of the extracted products.

Date of Award	15 Jul 2026
Original language	English
Awarding Institution	University of Nottingham
Supervisor	Yuanyuan Shao (Supervisor), Dongbing Li (Supervisor) & Xiaoyang Wei (Supervisor)