Effects of different extraction methods on the physicochemical properties and storage stability of tiger nut (Cyperus esculentus L.) oil

Tiger nut (Cyperus esculentus L.) tubers are promising resources in the oil industry due to their high yield and oil content. In this study, five tiger nut oils, namely, cold pressing oil (CPO), roasted-pressing oil (RPO), solvent leaching oil (LPO), aqueous enzymatic extraction oil (AEO), and subcritical fluid extraction oil (SEO) were obtained, with yields of 14.00%, 9.80%, 20.80%, 14.60%, and 23.50%, respectively. After accelerated storage, their unsaturated fatty acid contents and tocopherol contents decreased significantly by 2.20–3.59% and 8.66–23.07 mg/100 g, respectively. Aldehydes formed by oil oxidation were the main volatiles in CPO (58.478%), RPO (34.471%), and AEO (47.780%), while the main volatiles in LPO and SEO were still alkanes (38.488–40.210%). Oxidative deterioration of oils was also characterized by nuclear magnetic resonance, differential scanning calorimetry, and physicochemical properties (e.g., peroxide value, acid values, p-anisidine values, iodine values, 2-thiobarbituric acid levels, conjugated diene/triene values, refractive indices, and color). The above results all demonstrated the superior storage stability of LPO and SEO, which was also consistent with the high oxidative stability indices of LPO (125.0 h) and SEO (61.5 h) than other oils (4.8–11.8 h). This study will benefit to the development of tiger nut oil in the edible oil field.