Fast detection of adulteration of aromatic peanut oils based on alpha-tocopherol and gamma-tocopherol contents and ratio

A fast method based on normal-phase high-performance liquid chromatography with UV detection was applied to determine the tocopherols in aromatic peanut oil (APO) and four refined vegetable oils (soybean, sunflower, maize, and rapeseed oils). Our results showed that the tested oils varied greatly on the content of tocopherol isomers, especially on α- and γ-tocopherol concentrations. Consequently, (α+γ)-tocopherol (297.9–393.2 mg kg−1) and α-/γ-tocopherol (1.05–2.13) were successfully applied as discriminating parameters for detecting the adulteration of APO with above four refined vegetable oils. Furthermore, APO was mixed with the four oils (at the levels of 5, 10, 15, 20 and 25 g/100 g, w/w) to determine whether the tocopherol analysis is a better approach than fatty acid profiling for detecting APO adulteration. Our results showed that for tocopherols, our detection limits were 5 g/100 g for soybean oil and 10 g/100 g for other three oils in APO, showing a higher sensitivity than fatty acids profile based method for detecting APO adulteration. Thus, our newly developed method is an alternative and innovative tool for fast and cost-effective detection of the adulteration of APO with soybean, sunflower, maize, and rapeseed oils.