An efficient strategy to enhance the yield and quality of ethanol-extracted tiger nut (Cyperus esculentus L.) oil by combining high-speed blending with ultrasound-assisted extraction

Ethanol is a promising green alternative to conventional n -hexane as an oil extraction solvent; however, achieving high oil yields typically requires elevated temperatures (>80 °C) to enhance ethanol’s solvating capacity. In this study, ethanol-extracted oil (EO, 60 °C, 3 h) from tiger nut yielded 16.21%, which was lower than that obtained by n- hexane extraction (HO, 23.33%). Ethanol extraction assisted by 5-minute high-speed blending at 55 °C (BEO) enhanced extraction efficiency while preventing excessive temperature increases that could damage starch, resulting in an oil yield of 22.68%. This improvement was attributed to tiger nut being a unique high-starch oilseed. Effective cell wall disruption and dispersion of starch particles facilitated oil migration into ethanol, thereby reducing the dependence on high solvating capacity. To further improve oil quality, ultrasound treatment (60 °C, 30 min) was applied after high-speed blending to assist ethanol extraction, yielding UBEO. It achieved a higher oil yield (23.18%) than that of EO, BEO, HEO (extracted with n- hexane/ethanol), and MBEO (microwave-assisted pretreatment followed by high-speed blending). It also exhibited the highest phenolic content (15.75-fold that of HO) and the highest radical scavenging capacity among all oils. In conclusion, this work provides a new strategy for producing high-quality tiger nut oil. • Method to improve yield & quality of ethanol-extracted tiger nut oil (EO) developed • UBEO’s (high speed blending & ultrasound assisted ethanol) thermostability was best • UBEO's yield is 43.0% higher than EO's, with no obviously damage to meal starch • The phenolic content of UBEO was 15.75 times that of HO (extracted by n-hexane)