Composition, bioactive substances, extraction technologies and the influences on characteristics of Camellia oleifera oil: A review

C. oleifera oil is one of the high-quality edible oils recommended by the Food and Agriculture Organization of the United Nations (FAO). Pharmacological studies have shown that C. oleifera oil is the homology of medicine and food, and it possesses extensive beneficial health properties both in vivo and in vitro. C. oleifera oil found its application in the functional food, cosmetic, and pharmaceutical industries. In recent years, the need for high-quality and high-quantity production of C. oleifera oil for human consumption has increased. The present review examines the chemical composition of C. oleifera oil, bioactive substances, extraction technologies, and evidence supporting the health benefits of C. oleifera oil. From the reviewed studies, it appears that C. oleifera oil contains a significant proportion of unsaturated fatty acids (>85%) with oleic acid (>75%) as the major compound, and high contents of squalene, tea polyphenols, tocopherol and phytosterol. Some variations in C. oleifera oil composition can be found depending on the kernel's origin and the extraction method used. Emerging technologies such as aqueous extraction, and supercritical fluid extraction are highly efficient processes, and can achieve higher recovery while reducing solvent and energy consumption. This review provides an in-depth discussion on the various extraction technologies and factors affecting the extraction efficiency of C. oleifera oil using traditional and emerging methods. The influences of different extraction methods on the C. oleifera oil characteristics are also introduced. Furthermore, challenges and future prospects of the extraction of C. oleifera oil have been identified and discussed.