Comparison of the quality attributes of oils extracted from irradiated and non-irradiated tiger nuts by different methods

In this study, tiger nut oil was extracted from irradiated and non-irradiated tiger nuts with four different methods, namely cold pressing (CPE), hexane extraction (HE), aqueous enzyme extraction (AEE) and supercritical fluid extraction (SFE), and the quality characteristics of the obtained oil were determined. Results indicated that gamma irradiation increased the oil yield by 6.02–7.30%, depending on the extraction method used and had a negligible effect on the fatty acid composition of tiger nut oil. In addition, gamma irradiation significantly increased (p < 0.05) the acid value, peroxide value, K 232 and K 268 of oil, and reduced the amount of vitamin E, total phenolic, carotenoids and chlorophyll in the oil as well as its oxidation stability. However, the FTIR spectra of the irradiated and non-irradiated oil samples were almost identical. The above changes were verified in the oils obtained with different extraction methods. A total of eight irradiation-induced hydrocarbons were detected in the irradiated oil samples, mainly 1,7-hexadecadiene, 1-tetradecene and 8-heptadecene. The extraction method had no effect on the composition of radiolytic hydrocarbons, but the amount of radiolytic products in the oil extracted by SFE was much higher than other methods. • Tiger nuts were gamma irradiated and the oil was extracted by four different methods. • Gamma irradiation improved oil yield but reduced quality of oil from tiger nuts. • Hexane extracted oils had higher bioactive component content and oxidative stability. • Fourier transform infrared spectra (FTIR) of all oil samples were almost identical. • Extremely high levels of radiocarbons in oil extracted by supercritical fluids.