Synergistic phase behaviors of phytosterols and phytosterol esters in medium chain triglycerides

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.