Ultrasound-assisted development of stable grapefruit peel polyphenolic nano-emulsion: Optimization and application in improving oxidative stability of mustard oil

•Nano-emulsion (NE) of grapefruit peel phenolic/mustard oil (GPP/MO) was formulated.•RSM optimization revealed sonication aided formation of NE with droplet size <100 nm.•Morphological analysis revealed encapsulation of GPP inside the emulsion.•Antioxidant activities depicted synergistic interaction between GPP and MO.•GPP/MO-NE resulted in enhanced oxidative stability of virgin mustard oil.