It has been reported that vanillin has been intentionally added to enhance the taste and flavor of low-quality vegetable oils. Therefore, it is crucial to investigate the accurate concentrations of vanillin in three types of fragrant vegetable oils commonly consumed in China. In this study, a method has been developed for the quantification of vanillin in commercial fragrant vegetable oils using the stable isotope dilution assay (SIDA) and headspace–solid-phase microextraction (HS–SPME) coupled with gas chromatography/mass spectrometry (GC/MS). The limit of detection (LOD) and limit of quantification (LOQ) of the analyte were determined to be 20 µg kg⁻¹ and 50 µg kg⁻¹, respectively. The validation study demonstrated that the recoveries ranged from 89% to 101%, with intra-day and inter-day precision being less than 7.46%. A survey of 80 commercially available fragrant vegetable oils was performed using the present method. Vanillin was found to be widely present in fragrant vegetable oils, with sesame oils showing the highest average content (842.6 µg kg⁻¹), followed by rapeseed oils (262.1 µg kg⁻¹) and peanut oils (115.0 µg kg⁻¹). The results indicate that the proposed method is a simple, accurate, and eco-friendly approach for determining the presences of vanillin in fragrant vegetable oils.

Free phytosterols (PS) and phytosterol esters (PSE) usually coexist in natural oils, which significantly affect the crystallization behavior of oil. However, the phase behaviors of PS/PSE mixtures in oils and their roles on the crystallization behavior of oil are still unclear. In this study, the dissolution and crystallization behaviors of PS/PSE mixtures in medium chain triglyceride (MCT) were studied, and the synergistic mechanism of PS/PSE mixtures on the crystallization behaviors of MCT was further clarified. The results showed that when the mass ratio of PS: PSE was greater than 3: 7, PS/PSE mixtures recrystallized a new urchin-like crystal structure, which was different from PS spherical or PSE plate-like crystal structure, in MCT. The new urchin-like PS/PSE crystal had a larger surface area, and its melting point was between PS and PSE. It also showed the synergistic ability to promote the crystallization nucleation of MCT. When the total content of PS and PSE was 1 wt%, and the mass ratio of PS: PSE was 5: 5, the crystallization peak temperature of PS/PSE/MCT was 12 ºC higher than that of virgin MCT, 2.5 ºC higher than that of PSE/MCT, and 10.3 ºC higher than that of PS/MCT. These results not only provide a method for obtaining new crystal structure of phytosterols, but also have great significance for controlling the crystallization behaviors of oils by precisely adjusting the nutritional composition of oils.