Identification of camellia oil using FT-IR spectroscopy and chemometrics based on both isolated unsaponifiables and vegetable oils

Camellia oil is one of editable high-quality oils recommended by Food and Agriculture Organization. Thus the method to authenticate camellia oil is significant research. Saponification is one of the simple and inexpensive processes have been used to identify the adulteration in edible oil. At present, the saponification takes a long time, higher temperature and the isolation of unsaponifiables from saponifiables is tedious. In this research, the enriched saponification process has been developed using ultrasonication technique instead of a conventional reflux method. The process has been significantly reduced to 15 min at 55 °C from the regular saponification which need about 2 h by ISO 18609:2000. The special solid phase extraction (SPE) cartridge has been designed and prepared to separate the unsaponifiables, which separates the residual alkaline substance as well as absorbs water in the organic phase in a single cycle. PLS-DA is used to establish model I based on isolated unsaponifiables and model II based on of vegetable oils for identification of camellia oil. The combined FT-IR and chemometrics based on the isolated unsaponifiables was first used to authenticate vegetable oil. Model I had more sensitivity to discriminate adulterated camellia oils by adulterants whose fatty acid compositions similar to camellia oil such as hazelnut oil, soybean oil, corn oil and cheap mixed oil. On the contrary, model II had more sensitivity to discriminate adulterated camellia oils by adulterant whose fatty acid compositions were different from camellia oil such as palm oil. The results concluded that the FT-IR spectroscopy combined with chemometrics based on both isolated unsaponifiables and vegetable oils could be fast and effective to authenticate camellia oil.